Programs & Examples On #Consumer

Can't perform a React state update on an unmounted component

Inspired by the accepted answer by @ford04 I had even better approach dealing with it, instead of using useEffect inside useAsync create a new function that returns a callback for componentWillUnmount :

function asyncRequest(asyncRequest, onSuccess, onError, onComplete) {
  let isMounted=true
  asyncRequest().then((data => isMounted ? onSuccess(data):null)).catch(onError).finally(onComplete)
  return () => {isMounted=false}


        return asyncRequest(()=>someAsyncTask(arg), response=> {
        },onError, onComplete)

Android Gradle 5.0 Update:Cause: org.jetbrains.plugins.gradle.tooling.util

I solved this issue after changing the "Gradle Version" and "Android Plugin version".

You just goto "File>>Project Structure>>Project>>" and make changes here. I have worked a combination of versions from another working project of mine and added to the Project where I was getting this problem.

Java 8 optional: ifPresent return object orElseThrow exception

Two options here:

Replace ifPresent with map and use Function instead of Consumer

private String getStringIfObjectIsPresent(Optional<Object> object) {
    return object
            .map(obj -> {
                String result = "result";
                //some logic with result and return it
                return result;

Use isPresent:

private String getStringIfObjectIsPresent(Optional<Object> object) {
    if (object.isPresent()) {
        String result = "result";
        //some logic with result and return it
        return result;
    } else {
        throw new MyCustomException();

Kafka consumer list

Kafka stores all the information in zookeeper. You can see all the topic related information under brokers->topics. If you wish to get all the topics programmatically you can do that using Zookeeper API.

It is explained in detail in below links Tutorialspoint, Zookeeper Programmer guide

Spring Boot REST service exception handling

Solution with dispatcherServlet.setThrowExceptionIfNoHandlerFound(true); and @EnableWebMvc @ControllerAdvice worked for me with Spring Boot 1.3.1, while was not working on 1.2.7

Java, How to get number of messages in a topic in apache kafka

To get all the messages stored for the topic you can seek the consumer to the beginning and end of the stream for each partition and sum the results

List<TopicPartition> partitions = consumer.partitionsFor(topic).stream()
        .map(p -> new TopicPartition(topic, p.partition()))
Map<TopicPartition, Long> endPartitions =
        .collect(Collectors.toMap(Function.identity(), consumer::position));
System.out.println( -> endPartitions.get(p) - consumer.position(p)).sum());

Could not install Gradle distribution from ''

In my case I had to go to

File -> Settings -> Build, Execution, Deployment -> Gradle

and then I changed the Service directory path, which was pointing to a wrong location.

Python IndentationError unindent does not match any outer indentation level

make sure """ comments are only a tab away and not 5 spaces

How to extract hours and minutes from a datetime.datetime object?

datetime has fields hour and minute. So to get the hours and minutes, you would use t1.hour and t1.minute.

However, when you subtract two datetimes, the result is a timedelta, which only has the days and seconds fields. So you'll need to divide and multiply as necessary to get the numbers you need.

JSON ValueError: Expecting property name: line 1 column 2 (char 1)

  1. replace all single quotes with double quotes
  2. replace 'u"' from your strings to '"' ... so basically convert internal unicodes to strings before loading the string into json
>> strs = "{u'key':u'val'}"
>> strs = strs.replace("'",'"')
>> json.loads(strs.replace('u"','"'))

Error: org.springframework.web.HttpMediaTypeNotSupportedException: Content type 'text/plain;charset=UTF-8' not supported

For me it turned out that I had a @JsonManagedReferece in one entity without a @JsonBackReference in the other referenced entity. This caused the marshaller to throw an error.

Proper usage of Optional.ifPresent()

You can use method reference like this:


Method ifPresent() get Consumer object as a paremeter and (from JavaDoc): "If a value is present, invoke the specified consumer with the value." Value it is your variable user.

Or if this method doSomethingWithUser is in the User class and it is not static, you can use method reference like this:


"PKIX path building failed" and "unable to find valid certification path to requested target"

After struggling for half-day, found one more way to solve this problem. I was able to solve this in MAC 10.15.5 ( Catalina). Followed the below steps.

  • This problem occurs when we are running behind a company proxy , In my case its Zscaler.
  • Open Key chain access, export CA certificate.(Select CA certificate, File->export items and save with the desired name)
  • Copy the path of existing cacerts from java folder(/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/security/cacerts )
  • Open terminal and navigate to the Keytool folder (/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/bin )
  • Run the below command.
  • Keytool -importcert - file (Path to exported cert from the keychainaccess) -alias (give a name) -keystore (Path of existing cacerts from java folder)
  • sudo Keytool -importcert -file /Users/Desktop/RootCA.cer -alias demo -keystore /Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/security/cacerts
  • It will ask for password , give it as : changeit
  • It asks for confirmation , Say : yes

After all of these steps, Quit eclipse and terminal start fresh session.

android studio 0.4.2: Gradle project sync failed error

I had same problem but finally I could solve it forever

  1. Delete gradle and .gradle folders from your project folder.
  2. In Android Studio: Open your project then: File -> settings -> compiler -> gradle: enable offline mode
    Note: In relatively newer Android Studios, Offline mode has been moved to gradle setting. enter image description here
  3. Close your project: File -> close project
  4. Connect to the Internet and open your project again then let Android Studio downloads what it wants

If success then :)

  1. If you encounter gradle project sync failed again please follow these steps:
  2. Download the latest gradle package from this directory
  3. Extract it and put it somewhere (for example f:\gradle-1.10)
  4. Go to your Android Studio and load your project then open File->Settings->gradle, in this page click on Use local gradle distribution
  5. Type your gradle folder address there
    enter image description here

Congratulation you are done!

How can I send large messages with Kafka (over 15MB)?

One key thing to remember that message.max.bytes attribute must be in sync with the consumer's fetch.message.max.bytes property. the fetch size must be at least as large as the maximum message size otherwise there could be situation where producers can send messages larger than the consumer can consume/fetch. It might worth taking a look at it.
Which version of Kafka you are using? Also provide some more details trace that you are getting. is there some thing like ... payload size of xxxx larger than 1000000 coming up in the log?

Caused By: java.lang.NoClassDefFoundError: org/apache/log4j/Logger

java.lang.ClassNotFoundException is indicate that class is not found in class path. it could be the version of log4j is not compatible. check for different log4j version.

(.text+0x20): undefined reference to `main' and undefined reference to function

This rule

main: producer.o consumer.o AddRemove.o
   $(COMPILER) -pthread $(CCFLAGS) -o producer.o consumer.o AddRemove.o

is wrong. It says to create a file named producer.o (with -o producer.o), but you want to create a file named main. Please excuse the shouting, but ALWAYS USE $@ TO REFERENCE THE TARGET:

main: producer.o consumer.o AddRemove.o
   $(COMPILER) -pthread $(CCFLAGS) -o $@ producer.o consumer.o AddRemove.o

As Shahbaz rightly points out, the gmake professionals would also use $^ which expands to all the prerequisites in the rule. In general, if you find yourself repeating a string or name, you're doing it wrong and should use a variable, whether one of the built-ins or one you create.

main: producer.o consumer.o AddRemove.o
   $(COMPILER) -pthread $(CCFLAGS) -o $@ $^

what is Segmentation fault (core dumped)?

"Segmentation fault" means that you tried to access memory that you do not have access to.

The first problem is with your arguments of main. The main function should be int main(int argc, char *argv[]), and you should check that argc is at least 2 before accessing argv[1].

Also, since you're passing in a float to printf (which, by the way, gets converted to a double when passing to printf), you should use the %f format specifier. The %s format specifier is for strings ('\0'-terminated character arrays).

Ways to iterate over a list in Java

Example of each kind listed in the question:

import java.util.*;

public class ListIterationExample {

     public static void main(String []args){
        List<Integer> numbers = new ArrayList<Integer>();

        // populates list with initial values
        for (Integer i : Arrays.asList(0,1,2,3,4,5,6,7))
        printList(numbers);         // 0,1,2,3,4,5,6,7

        // replaces each element with twice its value
        for (int index=0; index < numbers.size(); index++) {
            numbers.set(index, numbers.get(index)*2); 
        printList(numbers);         // 0,2,4,6,8,10,12,14

        // does nothing because list is not being changed
        for (Integer number : numbers) {
            number++; // number = new Integer(number+1);
        printList(numbers);         // 0,2,4,6,8,10,12,14  

        // same as above -- just different syntax
        for (Iterator<Integer> iter = numbers.iterator(); iter.hasNext(); ) {
            Integer number =;
        printList(numbers);         // 0,2,4,6,8,10,12,14

        // ListIterator<?> provides an "add" method to insert elements
        // between the current element and the cursor
        for (ListIterator<Integer> iter = numbers.listIterator(); iter.hasNext(); ) {
            Integer number =;
            iter.add(number+1);     // insert a number right before this
        printList(numbers);         // 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15

        // Iterator<?> provides a "remove" method to delete elements
        // between the current element and the cursor
        for (Iterator<Integer> iter = numbers.iterator(); iter.hasNext(); ) {
            Integer number =;
            if (number % 2 == 0)    // if number is even 
                iter.remove();      // remove it from the collection
        printList(numbers);         // 1,3,5,7,9,11,13,15

        // ListIterator<?> provides a "set" method to replace elements
        for (ListIterator<Integer> iter = numbers.listIterator(); iter.hasNext(); ) {
            Integer number =;
            iter.set(number/2);     // divide each element by 2
        printList(numbers);         // 0,1,2,3,4,5,6,7

     public static void printList(List<Integer> numbers) {
        StringBuilder sb = new StringBuilder();
        for (Integer number : numbers) {
        sb.deleteCharAt(sb.length()-1); // remove trailing comma

Is there a way to delete all the data from a topic or delete the topic before every run?

For brew users

If you're using brew like me and wasted a lot of time searching for the infamous kafka-logs folder, fear no more. (and please do let me know if that works for you and multiple different versions of Homebrew, Kafka etc :) )

You're probably going to find it under:



How to actually find that path

(this is also helpful for basically every app you install through brew)

1) brew services list

kafka started matbhz /Users/matbhz/Library/LaunchAgents/homebrew.mxcl.kafka.plist

2) Open and read that plist you found above

3) Find the line defining location open it, in my case:

  • /usr/local/etc/kafka/

4) Look for the log.dirs line:


5) Go to that location and delete the logs for the topics you wish

6) Restart Kafka with brew services restart kafka

jquery AJAX and json format

Currently you are sending the data as typical POST values, which look like this:


If you want to send data as json you need to create an object with data and stringify it.

data: JSON.stringify(someobject)

Compare two DataFrames and output their differences side-by-side

Extending answer of @cge, which is pretty cool for more readability of result:

a[a != b][np.any(a != b, axis=1)].join(pd.DataFrame('a<->b', index=a.index, columns=['a<=>b'])).join(
        b[a != b][np.any(a != b, axis=1)]
        ,rsuffix='_b', how='outer'

Full demonstration example:

import numpy as np, pandas as pd

a = pd.DataFrame(np.random.randn(7,3), columns=list('ABC'))
b = a.copy()
b.iloc[0,2] = np.nan
b.iloc[1,0] = 7
b.iloc[3,1] = 77
b.iloc[4,2] = 777

a[a != b][np.any(a != b, axis=1)].join(pd.DataFrame('a<->b', index=a.index, columns=['a<=>b'])).join(
        b[a != b][np.any(a != b, axis=1)]
        ,rsuffix='_b', how='outer'

JSON, REST, SOAP, WSDL, and SOA: How do they all link together

Imagine you are developing a web-application and you decide to decouple the functionality from the presentation of the application, because it affords greater freedom.

You create an API and let others implement their own front-ends over it as well. What you just did here is implement an SOA methodology, i.e. using web-services.

Web services make functional building-blocks accessible over standard Internet protocols independent of platforms and programming languages.

So, you design an interchange mechanism between the back-end (web-service) that does the processing and generation of something useful, and the front-end (which consumes the data), which could be anything. (A web, mobile, or desktop application, or another web-service). The only limitation here is that the front-end and back-end must "speak" the same "language".

That's where SOAP and REST come in. They are standard ways you'd pick communicate with the web-service.


SOAP internally uses XML to send data back and forth. SOAP messages have rigid structure and the response XML then needs to be parsed. WSDL is a specification of what requests can be made, with which parameters, and what they will return. It is a complete specification of your API.


REST is a design concept.

The World Wide Web represents the largest implementation of a system conforming to the REST architectural style.

It isn't as rigid as SOAP. RESTful web-services use standard URIs and methods to make calls to the webservice. When you request a URI, it returns the representation of an object, that you can then perform operations upon (e.g. GET, PUT, POST, DELETE). You are not limited to picking XML to represent data, you could pick anything really (JSON included)

Flickr's REST API goes further and lets you return images as well.

JSON and XML, are functionally equivalent, and common choices. There are also RPC-based frameworks like GRPC based on Protobufs, and Apache Thrift that can be used for communication between the API producers and consumers. The most common format used by web APIs is JSON because of it is easy to use and parse in every language.

"Large data" workflows using pandas

Why Pandas ? Have you tried Standard Python ?

The use of standard library python. Pandas is subject to frequent updates, even with the recent release of the stable version.

Using the standard python library your code will always run.

One way of doing it is to have an idea of the way you want your data to be stored , and which questions you want to solve regarding the data. Then draw a schema of how you can organise your data (think tables) that will help you query the data, not necessarily normalisation.

You can make good use of :

  • list of dictionaries to store the data in memory (Think Amazon EC2) or disk, one dict being one row,
  • generators to process the data row after row to not overflow your RAM,
  • list comprehension to query your data,
  • make use of Counter, DefaultDict, ...
  • store your data on your hard drive using whatever storing solution you have chosen, json could be one of them.

Ram and HDD is becoming cheaper and cheaper with time and standard python 3 is widely available and stable.

The fondamental question you are trying to solve is "how to query large sets of data ?". The hdfs architecture is more or less what I am describing here (data modelling with data being stored on disk).

Let's say you have 1000 petabytes of data, there no way you will be able to store it in Dask or Pandas, your best chances here is to store it on disk and process it with generators.

API pagination best practices

You have several problems.

First, you have the example that you cited.

You also have a similar problem if rows are inserted, but in this case the user get duplicate data (arguably easier to manage than missing data, but still an issue).

If you are not snapshotting the original data set, then this is just a fact of life.

You can have the user make an explicit snapshot:

POST /createquery

Which results:

HTTP/1.1 301 Here's your query

Then you can page that all day long, since it's now static. This can be reasonably light weight, since you can just capture the actual document keys rather than the entire rows.

If the use case is simply that your users want (and need) all of the data, then you can simply give it to them:

GET /query/12345?all=true

and just send the whole kit.

Pagination response payload from a RESTful API

generally, I make by simple way, whatever, I create a restAPI endpoint for example "localhost/api/method/:lastIdObtained/:countDateToReturn" with theses parameters, you can do it a simple request. in the service, eg. .net

jsonData function(lastIdObtained,countDatetoReturn){
'... write your code as you wish..'
and into select query make a filter
select top countDatetoreturn,tt.desc
 from tbANyThing tt
where id > lastIdObtained
order by id

In Ionic, when I scroll from bottom to top, I pass the zero value, when I get the answer, I set the value of the last id obtained, and when I slide from top to bottom, I pass the last registration id I got

OAuth 2.0 Authorization Header

For those looking for an example of how to pass the OAuth2 authorization (access token) in the header (as opposed to using a request or body parameter), here is how it's done:

Authorization: Bearer 0b79bab50daca910b000d4f1a2b675d604257e42

Compare and contrast REST and SOAP web services?

In day to day, practical programming terms, the biggest difference is in the fact that with SOAP you are working with static and strongly defined data exchange formats where as with REST and JSON data exchange formatting is very loose by comparison. For example with SOAP you can validate that exchanged data matches an XSD schema. The XSD therefore serves as a 'contract' on how the client and the server are to understand how the data being exchanged must be structured.

JSON data is typically not passed around according to a strongly defined format (unless you're using a framework that supports it .. e.g. or implementing json-schema).

In-fact, some (many/most) would argue that the "dynamic" secret sauce of JSON goes against the philosophy/culture of constraining it by data contracts (Should JSON RESTful web services use data contract)

People used to working in dynamic loosely typed languages tend to feel more comfortable with the looseness of JSON while developers from strongly typed languages prefer XML.

RabbitMQ / AMQP: single queue, multiple consumers for same message?

To get the behavior you want, simply have each consumer consume from its own queue. You'll have to use a non-direct exchange type (topic, header, fanout) in order to get the message to all of the queues at once.

Celery Received unregistered task of type (run example)

An additional item to a really useful list.

I have found Celery unforgiving in relation to errors in tasks (or at least I haven't been able to trace the appropriate log entries) and it doesn't register them. I have had a number of issues with running Celery as a service, which have been predominantly permissions related.

The latest related to permissions writing to a log file. I had no issues in development or running celery at the command line, but the service reported the task as unregistered.

I needed to change the log folder permissions to enable the service to write to it.

Node.js setting up environment specific configs to be used with everyauth

set environment variable in deployment server(ex: like NODE_ENV=production). You can access your environmental variable through process.env.NODE_ENV. Find the following config file for the global settings

const env = process.env.NODE_ENV || "development"

const configs = {
    base: {
        host: '',
        port: 3000,
        dbPort: 3306,
        secret: "secretKey for sessions",
        dialect: 'mysql',
        issuer : 'Mysoft corp',
        subject : '[email protected]',
    development: {
        port: 3000,
        dbUser: 'root',
        dbPassword: 'root',

    smoke: {
        port: 3000,
        dbUser: 'root',
    integration: {
        port: 3000,
        dbUser: 'root',
    production: {
        port: 3000,
        dbUser: 'root',

const config = Object.assign(configs.base, configs[env]);

module.exports= config;

base contains common config for all environments.

then import in other modules like

const config =  require('path/to/config.js')

Happy Coding...

How to test web service using command line curl

From the documentation on :

HTTP Authentication

curl --user name:password 

Put a file to a HTTP server with curl:

curl --upload-file uploadfile

Send post data with curl:

curl --data "birthyear=1905&press=%20OK%20"

Get protocol, domain, and port from URL

window.location.origin will be enough to get the same.

Java: unable to find valid certification path to requested target

The problem appears when your server has self signed certificate. To workaround it you can add this certificate to the list of trusted certificates of your JVM.

In this article author describes how to fetch the certificate from your browser and add it to cacerts file of your JVM. You can either edit JAVA_HOME/jre/lib/security/cacerts file or run you application with parameter. Verify which JDK/JRE you are using too as this is often a source of confusion.

See also: How are SSL certificate server names resolved/Can I add alternative names using keytool? If you run into No name matching localhost found exception.

Ignore self-signed ssl cert using Jersey Client

Okay, I'd like to just add my class only because there might be some dev out there in the future that wants to connect to a Netbackup server (or something similar) and do stuff from Java while ignoring the SSL cert. This worked for me and we use windows active directory for auth to the Netbackup server.

public static void main(String[] args) throws Exception {
    SSLContext sslcontext = null;
    try {
        sslcontext = SSLContext.getInstance("TLS");
    } catch (NoSuchAlgorithmException ex) {
        Logger.getLogger(main.class.getName()).log(Level.SEVERE, null, ex);
    try {
        sslcontext.init(null, new TrustManager[]{new X509TrustManager() {
            public X509Certificate[] getAcceptedIssuers() {
                return new X509Certificate[0];
            public void checkClientTrusted(X509Certificate[] xcs, String string) throws CertificateException {
                //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.

            public void checkServerTrusted(X509Certificate[] xcs, String string) throws CertificateException {
                //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
        }}, new;
    } catch (KeyManagementException ex) {
        Logger.getLogger(main.class.getName()).log(Level.SEVERE, null, ex);
    //HttpAuthenticationFeature feature = HttpAuthenticationFeature.basicBuilder().credentials(username, password).build();
    ClientConfig clientConfig = new ClientConfig();
    Client client = ClientBuilder.newBuilder().withConfig(clientConfig)
            .hostnameVerifier((s1, s2) -> true)

    //String the_url = "https://the_server:1556/netbackup/security/cacert";
    String the_token;
        String the_url = "https://the_server:1556/netbackup/login";
        WebTarget webTarget =;

        Invocation.Builder invocationBuilder = webTarget.request(MediaType.APPLICATION_JSON);
        String jsonString = new JSONObject()
                .put("domainType", "NT")
                .put("domainName", "XX")
                .put("userName", "the username")
                .put("password", "the password").toString();
        Response response =;
        String data = response.readEntity(String.class);
        JSONObject jo = new JSONObject(data);
        the_token = jo.getString("token");
        System.out.println("token is:" + the_token);

        String the_url = "https://the_server:1556/netbackup/admin/jobs/1122012"; //job id 1122012 is an example
        WebTarget webTarget =;
        Invocation.Builder invocationBuilder = webTarget.request(MediaType.APPLICATION_JSON).header(HttpHeaders.AUTHORIZATION, the_token).header(HttpHeaders.ACCEPT, "application/vnd.netbackup+json;version=1.0");
        Response response = invocationBuilder.get();
        System.out.println("response status:" + response.getStatus());
        String data = response.readEntity(String.class);
        //JSONObject jo = new JSONObject(data);

I know it can be considered off-topic, but I bet the dev that tries to connect to a Netbackup server will probably end up here. By the way many thanks to all the answers in this question! The spec I'm talking about is here and their code samples are (currently) missing a Java example.

***This is of course unsafe since we ignore the cert!

How to check if an element exists in the xml using xpath?

Use the boolean() XPath function

The boolean function converts its argument to a boolean as follows:

  • a number is true if and only if it is neither positive or negative zero nor NaN

  • a node-set is true if and only if it is non-empty

  • a string is true if and only if its length is non-zero

  • an object of a type other than the four basic types is converted to a boolean in a way that is dependent on that type

If there is an AttachedXml in the CreditReport of primary Consumer, then it will return true().


JMS Topic vs Queues

Queue is JMS managed object used for holding messages waiting for subscribers to consume. When all subscribers consumed the message , message will be removed from queue.

Topic is that all subscribers to a topic receive the same message when the message is published.

Turning a Comma Separated string into individual rows

By creating this function ([DelimitedSplit]) which splits a string, you could do an OUTER APPLY to your SELECT.

CREATE FUNCTION [dbo].[DelimitedSplit]
--===== Define I/O parameters
        (@pString VARCHAR(8000), @pDelimiter CHAR(1))
--===== "Inline" CTE Driven "Tally Table" produces values from 1 up to 10,000...
     -- enough to cover VARCHAR(8000)
  WITH E1(N) AS (
                ),                          --10E+1 or 10 rows
       E2(N) AS (SELECT 1 FROM E1 a INNER JOIN E1 b ON b.N = a.N), --10E+2 or 100 rows
       E4(N) AS (SELECT 1 FROM E2 a INNER JOIN E2 b ON b.N = a.N), --10E+4 or 10,000 rows max
 cteTally(N) AS (--==== This provides the "base" CTE and limits the number of rows right up front
                     -- for both a performance gain and prevention of accidental "overruns"
cteStart(N1) AS (--==== This returns N+1 (starting position of each "element" just once for each delimiter)
                 SELECT 1 UNION ALL
                 SELECT t.N+1 FROM cteTally t WHERE SUBSTRING(@pString,t.N,1) = @pDelimiter
cteLen(N1,L1) AS(--==== Return start and length (for use in substring)
                 SELECT s.N1,
                   FROM cteStart s
--===== Do the actual split. The ISNULL/NULLIF combo handles the length for the final element when no delimiter is found.
        Item       = SUBSTRING(@pString, l.N1, l.L1)
   FROM cteLen l


    SomeID INT,
    OtherID INT,
    String VARCHAR(MAX)

INSERT #Testdata SELECT 1,  9, '18,20,22'
INSERT #Testdata SELECT 2,  8, '17,19'
INSERT #Testdata SELECT 3,  7, '13,19,20'
INSERT #Testdata SELECT 4,  6, ''
INSERT #Testdata SELECT 9, 11, '1,2,3,4'

FROM #Testdata
OUTER APPLY [dbo].[DelimitedSplit](String,',')

DROP TABLE #Testdata


SomeID  OtherID String      ItemNumber  Item
1       9       18,20,22    1           18
1       9       18,20,22    2           20
1       9       18,20,22    3           22
2       8       17,19       1           17
2       8       17,19       2           19
3       7       13,19,20    1           13
3       7       13,19,20    2           19
3       7       13,19,20    3           20
4       6       1   
9       11      1,2,3,4     1           1
9       11      1,2,3,4     2           2
9       11      1,2,3,4     3           3
9       11      1,2,3,4     4           4

How to Load RSA Private Key From File

Two things. First, you must base64 decode the mykey.pem file yourself. Second, the openssl private key format is specified in PKCS#1 as the RSAPrivateKey ASN.1 structure. It is not compatible with java's PKCS8EncodedKeySpec, which is based on the SubjectPublicKeyInfo ASN.1 structure. If you are willing to use the bouncycastle library you can use a few classes in the bouncycastle provider and bouncycastle PKIX libraries to make quick work of this.


import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.openssl.PEMKeyPair;
import org.bouncycastle.openssl.PEMParser;
import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;

// ...   

String keyPath = "mykey.pem";
BufferedReader br = new BufferedReader(new FileReader(keyPath));
Security.addProvider(new BouncyCastleProvider());
PEMParser pp = new PEMParser(br);
PEMKeyPair pemKeyPair = (PEMKeyPair) pp.readObject();
KeyPair kp = new JcaPEMKeyConverter().getKeyPair(pemKeyPair);
samlResponse.sign(Signature.getInstance("SHA1withRSA").toString(), kp.getPrivate(), certs);

Is there a max size for POST parameter content?

There is no defined maximum size for HTTP POST requests. If you notice such a limit then it's an arbitrary limitation of your HTTP Server/Client.

You might get a better answer if you tell how big the XML is.

What is PECS (Producer Extends Consumer Super)?

Covariance: accept subtypes
Contravariance: accept supertypes

Covariant types are read-only, while contravariant types are write-only.

Producer/Consumer threads using a Queue

Use this typesafe pattern with poison pills:

public sealed interface BaseMessage {

    final class ValidMessage<T> implements BaseMessage {

        private final T value;

        public ValidMessage(@Nonnull T value) {
            this.value = value;

        public T getValue() {
            return value;

        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            ValidMessage<?> that = (ValidMessage<?>) o;
            return value.equals(that.value);

        public int hashCode() {
            return Objects.hash(value);

        public String toString() {
            return "ValidMessage{value=%s}".formatted(value);

    final class PoisonedMessage implements BaseMessage {

        public static final PoisonedMessage INSTANCE = new PoisonedMessage();

        private PoisonedMessage() {

        public String toString() {
            return "PoisonedMessage{}";

public class Producer implements Callable<Void> {

    private final BlockingQueue<BaseMessage> messages;

    Producer(@Nonnull BlockingQueue<BaseMessage> messages) {
        this.messages = messages;

    public Void call() throws Exception {
        messages.put(new BaseMessage.ValidMessage<>(1));
        messages.put(new BaseMessage.ValidMessage<>(2));
        messages.put(new BaseMessage.ValidMessage<>(3));
        return null;

public class Consumer implements Callable<Void> {

    private final BlockingQueue<BaseMessage> messages;

    private final int maxPoisons;

    public Consumer(@Nonnull BlockingQueue<BaseMessage> messages, int maxPoisons) {
        this.messages = messages;
        this.maxPoisons = maxPoisons;

    public Void call() throws Exception {
        int poisonsReceived = 0;
        while (poisonsReceived < maxPoisons && !Thread.currentThread().isInterrupted()) {
            BaseMessage message = messages.take();
            if (message instanceof BaseMessage.ValidMessage<?> vm) {
                Integer value = (Integer) vm.getValue();
            } else if (message instanceof BaseMessage.PoisonedMessage) {
            } else {
                throw new IllegalArgumentException("Invalid BaseMessage type: " + message);
        return null;

Create a custom callback in JavaScript

Some of the answers, while correct may be a little tricky to understand. Here is an example in layman's terms:

var users = ["Sam", "Ellie", "Bernie"];

function addUser(username, callback)
    }, 200);

function getUsers()
    }, 100);

addUser("Jake", getUsers);

The callback means, "Jake" is always added to the users before displaying the list of users with console.log.

Source (YouTube)

What is an application binary interface (ABI)?


There are various interpretation and strong opinions of the exact layer that define an ABI (application binary interface).

In my view an ABI is a subjective convention of what is considered a given/platform for a specific API. The ABI is the "rest" of conventions that "will not change" for a specific API or that will be addressed by the runtime environment: executors, tools, linkers, compilers, jvm, and OS.

Defining an Interface: ABI, API

If you want to use a library like joda-time you must declare a dependency on joda-time-<major>.<minor>.<patch>.jar. The library follows best practices and use Semantic Versioning. This defines the API compatibility at three levels:

  1. Patch - You don't need to change at all your code. The library just fixes some bugs.
  2. Minor - You don't need to change your code since the additions
  3. Major - The interface (API) is changed and you might need to change your code.

In order for you to use a new major release of the same library a lot of other conventions are still to be respected:

  • The binary language used for the libraries (in Java cases the JVM target version that defines the Java bytecode)
  • Calling conventions
  • JVM conventions
  • Linking conventions
  • Runtime conventions All these are defined and managed by the tools we use.


Java case study

For example, Java standardized all these conventions, not in a tool, but in a formal JVM specification. The specification allowed other vendors to provide a different set of tools that can output compatible libraries.

Java provides two other interesting case studies for ABI: Scala versions and Dalvik virtual machine.

Dalvik virtual machine broke the ABI

The Dalvik VM needs a different type of bytecode than the Java bytecode. The Dalvik libraries are obtained by converting the Java bytecode (with same API) for Dalvik. In this way you can get two versions of the same API: defined by the original joda-time-1.7.2.jar. We could call it joda-time-1.7.2.jar and joda-time-1.7.2-dalvik.jar. They use a different ABI one is for the stack-oriented standard Java vms: Oracle's one, IBM's one, open Java or any other; and the second ABI is the one around Dalvik.

Scala successive releases are incompatible

Scala doesn't have binary compatibility between minor Scala versions: 2.X . For this reason the same API "io.reactivex" %% "rxscala" % "0.26.5" has three versions (in the future more): for Scala 2.10, 2.11 and 2.12. What is changed? I don't know for now, but the binaries are not compatible. Probably the latest versions adds things that make the libraries unusable on the old virtual machines, probably things related to linking/naming/parameter conventions.

Java successive releases are incompatible

Java has problems with the major releases of the JVM too: 4,5,6,7,8,9. They offer only backward compatibility. Jvm9 knows how to run code compiled/targeted (javac's -target option) for all other versions, while JVM 4 doesn't know how to run code targeted for JVM 5. All these while you have one joda-library. This incompatibility flies bellow the radar thanks to different solutions:

  1. Semantic versioning: when libraries target higher JVM they usually change the major version.
  2. Use JVM 4 as the ABI, and you're safe.
  3. Java 9 adds a specification on how you can include bytecode for specific targeted JVM in the same library.

Why did I start with the API definition?

API and ABI are just conventions on how you define compatibility. The lower layers are generic in respect of a plethora of high level semantics. That's why it's easy to make some conventions. The first kind of conventions are about memory alignment, byte encoding, calling conventions, big and little endian encodings, etc. On top of them you get the executable conventions like others described, linking conventions, intermediate byte code like the one used by Java or LLVM IR used by GCC. Third you get conventions on how to find libraries, how to load them (see Java classloaders). As you go higher and higher in concepts you have new conventions that you consider as a given. That's why they didn't made it to the semantic versioning. They are implicit or collapsed in the major version. We could amend semantic versioning with <major>-<minor>-<patch>-<platform/ABI>. This is what is actually happening already: platform is already a rpm, dll, jar (JVM bytecode), war(jvm+web server), apk, 2.11 (specific Scala version) and so on. When you say APK you already talk about a specific ABI part of your API.

API can be ported to different ABI

The top level of an abstraction (the sources written against the highest API can be recompiled/ported to any other lower level abstraction.

Let's say I have some sources for rxscala. If the Scala tools are changed I can recompile them to that. If the JVM changes I could have automatic conversions from the old machine to the new one without bothering with the high level concepts. While porting might be difficult will help any other client. If a new operating system is created using a totally different assembler code a translator can be created.

APIs ported across languages

There are APIs that are ported in multiple languages like reactive streams. In general they define mappings to specific languages/platforms. I would argue that the API is the master specification formally defined in human language or even a specific programming language. All the other "mappings" are ABI in a sense, else more API than the usual ABI. The same is happening with the REST interfaces.

Can a CSV file have a comment?

No, CSV doesn't specify any way of tagging comments - they will just be loaded by programs like Excel as additional cells containing text.

The closest you can manage (with CSV being imported into a specific application such as Excel) is to define a special way of tagging comments that Excel will ignore. For Excel, you can "hide" the comment (to a limited degree) by embedding it into a formula. For example, try importing the following csv file into Excel:

=N("This is a comment and will appear as a simple zero value in excel")
John, Doe, 24

You still end up with a cell in the spreadsheet that displays the number 0, but the comment is hidden.

Alternatively, you can hide the text by simply padding it out with spaces so that it isn't displayed in the visible part of cell:

                              This is a sort-of hidden comment!,
John, Doe, 24

Note that you need to follow the comment text with a comma so that Excel fills the following cell and thus hides any part of the text that doesn't fit in the cell.

Nasty hacks, which will only work with Excel, but they may suffice to make your output look a little bit tidier after importing.

Understanding generators in Python

There is no Java equivalent.

Here is a bit of a contrived example:

#! /usr/bin/python
def  mygen(n):
    x = 0
    while x < n:
        x = x + 1
        if x % 3 == 0:
            yield x

for a in mygen(100):
    print a

There is a loop in the generator that runs from 0 to n, and if the loop variable is a multiple of 3, it yields the variable.

During each iteration of the for loop the generator is executed. If it is the first time the generator executes, it starts at the beginning, otherwise it continues from the previous time it yielded.

Which concurrent Queue implementation should I use in Java?

ConcurrentLinkedQueue means no locks are taken (i.e. no synchronized(this) or Lock.lock calls). It will use a CAS - Compare and Swap operation during modifications to see if the head/tail node is still the same as when it started. If so, the operation succeeds. If the head/tail node is different, it will spin around and try again.

LinkedBlockingQueue will take a lock before any modification. So your offer calls would block until they get the lock. You can use the offer overload that takes a TimeUnit to say you are only willing to wait X amount of time before abandoning the add (usually good for message type queues where the message is stale after X number of milliseconds).

Fairness means that the Lock implementation will keep the threads ordered. Meaning if Thread A enters and then Thread B enters, Thread A will get the lock first. With no fairness, it is undefined really what happens. It will most likely be the next thread that gets scheduled.

As for which one to use, it depends. I tend to use ConcurrentLinkedQueue because the time it takes my producers to get work to put onto the queue is diverse. I don't have a lot of producers producing at the exact same moment. But the consumer side is more complicated because poll won't go into a nice sleep state. You have to handle that yourself.

How to use ConcurrentLinkedQueue?

This is largely a duplicate of another question.

Here's the section of that answer that is relevant to this question:

Do I need to do my own synchronization if I use java.util.ConcurrentLinkedQueue?

Atomic operations on the concurrent collections are synchronized for you. In other words, each individual call to the queue is guaranteed thread-safe without any action on your part. What is not guaranteed thread-safe are any operations you perform on the collection that are non-atomic.

For example, this is threadsafe without any action on your part:




However; non-atomic calls to the queue are not automatically thread-safe. For example, the following operations are not automatically threadsafe:

if(!queue.isEmpty()) {

That last one is not threadsafe, as it is very possible that between the time isEmpty is called and the time poll is called, other threads will have added or removed items from the queue. The threadsafe way to perform this is like this:

synchronized(queue) {
    if(!queue.isEmpty()) {

Again...atomic calls to the queue are automatically thread-safe. Non-atomic calls are not.

Disposing WPF User Controls

An UserControl has a Destructor, why don't you use that?

        // Dispose of any Disposable items here

Why does PEP-8 specify a maximum line length of 79 characters?

I am a programmer who has to deal with a lot of code on a daily basis. Open source and what has been developed in house.

As a programmer, I find it useful to have many source files open at once, and often organise my desktop on my (widescreen) monitor so that two source files are side by side. I might be programming in both, or just reading one and programming in the other.

I find it dissatisfying and frustrating when one of those source files is >120 characters in width, because it means I can't comfortably fit a line of code on a line of screen. It upsets formatting to line wrap.

I say '120' because that's the level to which I would get annoyed at code being wider than. After that many characters, you should be splitting across lines for readability, let alone coding standards.

I write code with 80 columns in mind. This is just so that when I do leak over that boundary, it's not such a bad thing.

Node.js request CERT_HAS_EXPIRED

The best way to fix this:

Renew the certificate. This can be done for free using Greenlock which issues certificates via Let's Encrypt™ v2

A less insecure way to fix this:

'use strict';

var request = require('request');
var agentOptions;
var agent;

agentOptions = {
  host: ''
, port: '443'
, path: '/'
, rejectUnauthorized: false

agent = new https.Agent(agentOptions);

  url: ""
, method: 'GET'
, agent: agent
}, function (err, resp, body) {
  // ...

By using an agent with rejectUnauthorized you at least limit the security vulnerability to the requests that deal with that one site instead of making your entire node process completely, utterly insecure.

Other Options

If you were using a self-signed cert you would add this option: = [ selfSignedRootCaPemCrtBuffer ];

For trusted-peer connections you would also add these 2 options:

agentOptions.key = clientPemKeyBuffer;
agentOptions.cert = clientPemCrtSignedBySelfSignedRootCaBuffer;

Bad Idea

It's unfortunate that process.env.NODE_TLS_REJECT_UNAUTHORIZED = '0'; is even documented. It should only be used for debugging and should never make it into in sort of code that runs in the wild. Almost every library that runs atop https has a way of passing agent options through. Those that don't should be fixed.

ExpressionChangedAfterItHasBeenCheckedError Explained

I was facing the same problem as value was changing in one of the array in my component. But instead of detecting the changes on value change, I changed the component change detection strategy to onPush (which will detect changes on object change and not on value change).

import { Component, OnInit, ChangeDetectionStrategy } from '@angular/core';

    changeDetection: ChangeDetectionStrategy.OnPush
    selector: -

Java Try Catch Finally blocks without Catch

Regardless of exception thrown or not in try block - finally block will be executed. Exception would not be caught.

Specifying width and height as percentages without skewing photo proportions in HTML

You can set one or the other (just not both) and that should get the result you want.

<img src="#" height="50%">

How to clear/remove observable bindings in Knockout.js?

I think it might be better to keep the binding the entire time, and simply update the data associated with it. I ran into this issue, and found that just calling using the .resetAll() method on the array in which I was keeping my data was the most effective way to do this.

Basically you can start with some global var which contains data to be rendered via the ViewModel:

var myLiveData = ko.observableArray();

It took me a while to realize I couldn't just make myLiveData a normal array -- the ko.oberservableArray part was important.

Then you can go ahead and do whatever you want to myLiveData. For instance, make a $.getJSON call:

$.getJSON("", function(data) {
    /* parse the JSON data however you want, get it into myLiveData, as below */

Once you've done this, you can go ahead and apply bindings using your ViewModel as usual:

function MyViewModel() {
    var self = this;
    self.myData = myLiveData;
ko.applyBindings(new MyViewModel());

Then in the HTML just use myData as you normally would.

This way, you can just muck with myLiveData from whichever function. For instance, if you want to update every few seconds, just wrap that $.getJSON line in a function and call setInterval on it. You'll never need to remove the binding as long as you remember to keep the myLiveData.removeAll(); line in.

Unless your data is really huge, user's won't even be able to notice the time in between resetting the array and then adding the most-current data back in.

How to add days to the current date?

In SQL Server 2008 and above just do this:

SELECT DATEADD(day, 1, Getdate()) AS DateAdd;

How to remove the last character from a bash grep output

This will remove the last character contained in your COMPANY_NAME var regardless if it is or not a semicolon:

echo "$COMPANY_NAME" | rev | cut -c 2- | rev

Best Free Text Editor Supporting *More Than* 4GB Files?

Textpad also works well at opening files that size. I have done it many times when having to deal with extremely large log files in the 3-5gb range. Also, using grep to pull out the worthwhile lines and then look at those works great.

Post order traversal of binary tree without recursion

Here is a Python version too ::

class Node:
    def __init__(self,data): = data
        self.left = None
        self.right = None

def postOrderIterative(root):

    if root is None :

    s1 = []
    s2 = []

        node = s1.pop()



        node = s2.pop()

root = Node(1)
root.left = Node(2)
root.right = Node(3)
root.left.left = Node(4)
root.left.right = Node(5)
root.right.left = Node(6)
root.right.right = Node(7)

Here is the output ::

enter image description here

How to place and center text in an SVG rectangle

An easy solution to center text horizontally and vertically in SVG:

  1. Set the position of the text to the absolute center of the element in which you want to center it:

    • If it's the parent, you could just do x="50%" y ="50%".
    • If it's another element, x would be the x of that element + half its width (and similar for y but with the height).
  2. Use the text-anchor property to center the text horizontally with the value middle:


    The rendered characters are aligned such that the geometric middle of the resulting rendered text is at the initial current text position.

  3. Use the dominant-baseline property to center the text vertically with the value middle (or depending on how you want it to look like, you may want to do central)

Here is a simple demo:

<svg width="200" height="100">_x000D_
  <rect x="0" y="0" width="200" height="100" stroke="red" stroke-width="3px" fill="white"/>_x000D_
  <text x="50%" y="50%" dominant-baseline="middle" text-anchor="middle">TEXT</text>    _x000D_

How to get distinct results in hibernate with joins and row-based limiting (paging)?

A small improvement to @FishBoy's suggestion is to use the id projection, so you don't have to hard-code the identifier property name.


Excel VBA Password via Hex Editor

I have your answer, as I just had the same problem today:

Someone made a working vba code that changes the vba protection password to "macro", for all excel files, including .xlsm (2007+ versions). You can see how it works by browsing his code.

This is the guy's blog: Here's the file that does the work:

Pasted from a previous post from his blog:

For Excel 2007/2010 (.xlsm) files do following steps:

  1. Create a new .xlsm file.
  2. In the VBA part, set a simple password (for instance 'macro').
  3. Save the file and exit.
  4. Change file extention to '.zip', open it by any archiver program.
  5. Find the file: 'vbaProject.bin' (in 'xl' folder).
  6. Extract it from archive.
  7. Open the file you just extracted with a hex editor.
  8. Find and copy the value from parameter DPB (value in quotation mark), example: DPB="282A84CBA1CBA1345FCCB154E20721DE77F7D2378D0EAC90427A22021A46E9CE6F17188A". (This value generated for 'macro' password. You can use this DPB value to skip steps 1-8)

  9. Do steps 4-7 for file with unknown password (file you want to unlock).

  10. Change DBP value in this file on value that you have copied in step 8.

    If copied value is shorter than in encrypted file you should populate missing characters with 0 (zero). If value is longer - that is not a problem (paste it as is).

  11. Save the 'vbaProject.bin' file and exit from hex editor.

  12. Replace existing 'vbaProject.bin' file with modified one.
  13. Change extention from '.zip' back to '.xlsm'
  14. Now, open the excel file you need to see the VBA code in. The password for the VBA code will simply be macro (as in the example I'm showing here).

What is the difference between association, aggregation and composition?

Problem with these answers is they are half the story: they explain that aggregation and composition are forms of association, but they don't say if it is possible for an association to be neither of those.

I gather based on some brief readings of many posts on SO and some UML docs that there are 4 main concrete forms of class association:

  1. composition: A is-composed-of-a B; B doesn't exist without A, like a room in a home
  2. aggregation: A has-a B; B can exist without A, like a student in a classroom
  3. dependency: A uses-a B; no lifecycle dependency between A and B, like a method call parameter, return value, or a temporary created during a method call
  4. generalization: A is-a B

When a relationship between two entities isn't one of these, it can just be called "an association" in the generic sense of the term, and further described other ways (note, stereotype, etc).

My guess is that the "generic association" is intended to be used primarily in two circumstances:

  • when the specifics of a relationship are still being worked out; such relationship in a diagram should be converted as soon as possible to what it actually is/will be (one of the other 4).
  • when a relationship doesn't match any of those 4 predetermined by UML; the "generic" association still gives you a way of representing a relationship that is "not one of the other ones", so that you aren't stuck using an incorrect relationship with a note "this is not actually aggregation, it's just that UML doesn't have any other symbol we could use"

Create a dropdown component

If you want something with a dropdown (some list of values) and a user specified value that can be filled into the selected input as well. This custom dropdown in angular also has a filter dropdown list on key value entered. Please check this stackblitzlink ->

JQuery - File attributes

The input.files attribute is an HTML5 feature. That's why some browsers din't return anything. Simply add a fallback to the plain old input.value (string) if files doesn't exist.


Turning Sonar off for certain code

You can annotate a class or a method with SuppressWarnings


squid:S00112 in this case is a Sonar issue ID. You can find this ID in the Sonar UI. Go to Issues Drilldown. Find an issue you want to suppress warnings on. In the red issue box in your code is there a Rule link with a definition of a given issue. Once you click that you will see the ID at the top of the page.

How to change environment's font size?

After Pressing Control+Shift+P as suggested by @Edwin:

  1. Look for Workspace Settings:

enter image description here

  1. Then "Place your settings in the file to the right to overwrite...default and user settings," or click the UserSettings tab to adjust the window.zoomLevel if that is the desired action.

enter image description here

When is std::weak_ptr useful?

Another answer, hopefully simpler. (for fellow googlers)

Suppose you have Team and Member objects.

Obviously it's a relationship : the Team object will have pointers to its Members. And it's likely that the members will also have a back pointer to their Team object.

Then you have a dependency cycle. If you use shared_ptr, objects will no longer be automatically freed when you abandon reference on them, because they reference each other in a cyclic way. This is a memory leak.

You break this by using weak_ptr. The "owner" typically use shared_ptr and the "owned" use a weak_ptr to its parent, and convert it temporarily to shared_ptr when it needs access to its parent.

Store a weak ptr :

weak_ptr<Parent> parentWeakPtr_ = parentSharedPtr; // automatic conversion to weak from shared

then use it when needed

shared_ptr<Parent> tempParentSharedPtr = parentWeakPtr_.lock(); // on the stack, from the weak ptr
if( !tempParentSharedPtr ) {
  // yes, it may fail if the parent was freed since we stored weak_ptr
} else {
  // do stuff
// tempParentSharedPtr is released when it goes out of scope

What is the difference between and re.match?

re.match attempts to match a pattern at the beginning of the string. attempts to match the pattern throughout the string until it finds a match.

How to download the latest artifact from Artifactory repository?

You could also use Artifactory Query Language to get the latest artifact.

The following shell script is just an example. It uses 'items.find()' (which is available in the non-Pro version), e.g. items.find({ "repo": {"$eq":"my-repo"}, "name": {"$match" : "my-file*"}}) that searches for files that have a repository name equal to "my-repo" and match all files that start with "my-file". Then it uses the shell JSON parser ./jq to extract the latest file by sorting by the date field 'updated'. Finally it uses wget to download the artifact.


# Artifactory settings

# Use Artifactory Query Language to get the latest scraper script (
resultAsJson=$(curl -u$username:"$password" -X POST  http://$host/artifactory/api/search/aql -H "content-type: text/plain" -d 'items.find({ "repo": {"$eq":"my-repo"}, "name": {"$match" : "my-file*"}})')

# Use ./jq to pars JSON
latestFile=$(echo $resultAsJson | jq -r '.results | sort_by(.updated) [-1].name')

# Download the latest scraper script
wget -N -P ./libs/ --user $username --password $password http://$host/artifactory/my-repo/$latestFile

Make one div visible and another invisible

If u want to use display=block it will make the content reader jump, so instead of using display you can set the left attribute to a negative value which does not exist in your html page to be displayed but actually it do.

I hope you must be understanding my point, if I am unable to make u understand u can message me back.

Converting Stream to String and back...what are we missing?

a UTF8 MemoryStream to String conversion:

var res = Encoding.UTF8.GetString(stream.GetBuffer(), 0 , (int)stream.Length)

Concatenating bits in VHDL

The concatenation operator '&' is allowed on the right side of the signal assignment operator '<=', only

Convert generic List/Enumerable to DataTable?

If you are using VB.NET then this class does the job.

Imports System.Reflection
''' <summary>
''' Convert any List(Of T) to a DataTable with correct column types and converts Nullable Type values to DBNull
''' </summary>

Public Class ConvertListToDataset

    Public Function ListToDataset(Of T)(ByVal list As IList(Of T)) As DataTable

        Dim dt As New DataTable()
        '/* Create the DataTable columns */
        For Each pi As PropertyInfo In GetType(T).GetProperties()
            If pi.PropertyType.IsValueType Then
            End If
            If IsNothing(Nullable.GetUnderlyingType(pi.PropertyType)) Then
                dt.Columns.Add(pi.Name, pi.PropertyType)
                dt.Columns.Add(pi.Name, Nullable.GetUnderlyingType(pi.PropertyType))
            End If

        '/* Populate the DataTable with the values in the Items in List */
        For Each item As T In list
            Dim dr As DataRow = dt.NewRow()
            For Each pi As PropertyInfo In GetType(T).GetProperties()
                dr(pi.Name) = IIf(IsNothing(pi.GetValue(item)), DBNull.Value, pi.GetValue(item))
        Return dt

    End Function

End Class

How can I resolve the error "The security token included in the request is invalid" when running aws iam upload-server-certificate?

This is weird, but in my case whenever I wanted to retype the access id and the key by typing aws configure.

Adding the id access end up always with a mess in the access id entry in the file located ~/.aws/credentials(see the picture) The messed access id

I have removed this mess and left only the access id. And the error resolved.

Convert time in HH:MM:SS format to seconds only?

You can use the strtotime function to return the number of seconds from today 00:00:00.

$seconds= strtotime($time) - strtotime('00:00:00');

How to solve "Kernel panic - not syncing - Attempted to kill init" -- without erasing any user data

Booting from CD to rescue the installation and editing /etc/selinux/config: changed SELINUX from enforcing to permissive. Rebooted and system booted

/etc/selinux/config before change:

SELINUX=enforcing and SELINUXTYPE=permissive

/etc/selinux/config after change: SELINUX=permissive and SELINUXTYPE=permissive

Overlaying histograms with ggplot2 in R

While only a few lines are required to plot multiple/overlapping histograms in ggplot2, the results are't always satisfactory. There needs to be proper use of borders and coloring to ensure the eye can differentiate between histograms.

The following functions balance border colors, opacities, and superimposed density plots to enable the viewer to differentiate among distributions.

Single histogram:

plot_histogram <- function(df, feature) {
    plt <- ggplot(df, aes(x=eval(parse(text=feature)))) +
    geom_histogram(aes(y = ..density..), alpha=0.7, fill="#33AADE", color="black") +
    geom_density(alpha=0.3, fill="red") +
    geom_vline(aes(xintercept=mean(eval(parse(text=feature)))), color="black", linetype="dashed", size=1) +
    labs(x=feature, y = "Density")

Multiple histogram:

plot_multi_histogram <- function(df, feature, label_column) {
    plt <- ggplot(df, aes(x=eval(parse(text=feature)), fill=eval(parse(text=label_column)))) +
    geom_histogram(alpha=0.7, position="identity", aes(y = ..density..), color="black") +
    geom_density(alpha=0.7) +
    geom_vline(aes(xintercept=mean(eval(parse(text=feature)))), color="black", linetype="dashed", size=1) +
    labs(x=feature, y = "Density")
    plt + guides(fill=guide_legend(title=label_column))


Simply pass your data frame into the above functions along with desired arguments:

plot_histogram(iris, 'Sepal.Width')

enter image description here

plot_multi_histogram(iris, 'Sepal.Width', 'Species')

enter image description here

The extra parameter in plot_multi_histogram is the name of the column containing the category labels.

We can see this more dramatically by creating a dataframe with many different distribution means:

a <-data.frame(n=rnorm(1000, mean = 1), category=rep('A', 1000))
b <-data.frame(n=rnorm(1000, mean = 2), category=rep('B', 1000))
c <-data.frame(n=rnorm(1000, mean = 3), category=rep('C', 1000))
d <-data.frame(n=rnorm(1000, mean = 4), category=rep('D', 1000))
e <-data.frame(n=rnorm(1000, mean = 5), category=rep('E', 1000))
f <-data.frame(n=rnorm(1000, mean = 6), category=rep('F', 1000))
many_distros <-'rbind', list(a,b,c,d,e,f))

Passing data frame in as before (and widening chart using options):

options(repr.plot.width = 20, repr.plot.height = 8)
plot_multi_histogram(many_distros, 'n', 'category')

enter image description here

What is the difference between signed and unsigned variables?

unsigned is used when ur value must be positive, no negative value here, if signed for int range -32768 to +32767 if unsigned for int range 0 to 65535

add allow_url_fopen to my php.ini using .htaccess

allow_url_fopen is generally set to On. If it is not On, then you can try two things.

  1. Create an .htaccess file and keep it in root folder ( sometimes it may need to place it one step back folder of the root) and paste this code there.

    php_value allow_url_fopen On
  2. Create a php.ini file (for update server php5.ini) and keep it in root folder (sometimes it may need to place it one step back folder of the root) and paste the following code there:

    allow_url_fopen = On;

I have personally tested the above solutions; they worked for me.

Create a directly-executable cross-platform GUI app using Python

There's also PyGTK, which is basically a Python wrapper for the Gnome Toolkit. I've found it easier to wrap my mind around than Tkinter, coming from pretty much no knowledge of GUI programming previously. It works pretty well and has some good tutorials. Unfortunately there isn't an installer for Python 2.6 for Windows yet, and may not be for a while.

How do I uniquely identify computers visiting my web site?

I would do this using a combination of cookies and flash cookies. Create a GUID and store it in a cookie. If the cookie doesn't exist, try to read it from the flash cookie. If it's still not found, create it and write it to the flash cookie. This way you can share the same GUID across browsers.

Drawing circles with System.Drawing

With this code you can easily draw a circle... C# is great and easy my friend

public partial class Form1 : Form

public Form1()

  private void button1_Click(object sender, EventArgs e)
        Graphics myGraphics = base.CreateGraphics();
        Pen myPen = new Pen(Color.Red);
        SolidBrush mySolidBrush = new SolidBrush(Color.Red);
        myGraphics.DrawEllipse(myPen, 50, 50, 150, 150);

Update only specific fields in a models.Model

To update a subset of fields, you can use update_fields:["active"]) 

The update_fields argument was added in Django 1.5. In earlier versions, you could use the update() method instead:


How to group by week in MySQL?

Figured it out... it's a little cumbersome, but here it is.


And, if your business rules say your weeks start on Mondays, change the -1 to -2.


Years have gone by and I've finally gotten around to writing this up.

How can I see the raw SQL queries Django is running?

Django-extensions have a command shell_plus with a parameter print-sql

./ shell_plus --print-sql

In django-shell all executed queries will be printed


SELECT "auth_user"."id",
FROM "auth_user"
WHERE "auth_user"."id" = 1

Execution time: 0.002466s [Database: default]

<User: username>

C# create simple xml file

I'd recommend serialization,

public class Person
      public  string FirstName;
      public  string MI;
      public  string LastName;

static void Serialize()
      clsPerson p = new Person();
      p.FirstName = "Jeff";
      p.MI = "A";
      p.LastName = "Price";
      System.Xml.Serialization.XmlSerializer x = new System.Xml.Serialization.XmlSerializer(p.GetType());
      x.Serialize(System.Console.Out, p);
      System.Console.WriteLine(" --- Press any key to continue --- ");

You can further control serialization with attributes.
But if it is simple, you could use XmlDocument:

using System;
using System.Xml;

public class GenerateXml {
    private static void Main() {
        XmlDocument doc = new XmlDocument();
        XmlNode docNode = doc.CreateXmlDeclaration("1.0", "UTF-8", null);

        XmlNode productsNode = doc.CreateElement("products");

        XmlNode productNode = doc.CreateElement("product");
        XmlAttribute productAttribute = doc.CreateAttribute("id");
        productAttribute.Value = "01";

        XmlNode nameNode = doc.CreateElement("Name");
        XmlNode priceNode = doc.CreateElement("Price");

        // Create and add another product node.
        productNode = doc.CreateElement("product");
        productAttribute = doc.CreateAttribute("id");
        productAttribute.Value = "02";
        nameNode = doc.CreateElement("Name");
        priceNode = doc.CreateElement("Price");


And if it needs to be fast, use XmlWriter:

public static void WriteXML()
    // Create an XmlWriterSettings object with the correct options.
    System.Xml.XmlWriterSettings settings = new System.Xml.XmlWriterSettings();
    settings.Indent = true;
    settings.IndentChars = "    "; //  "\t";
    settings.OmitXmlDeclaration = false;
    settings.Encoding = System.Text.Encoding.UTF8;

    using (System.Xml.XmlWriter writer = System.Xml.XmlWriter.Create("data.xml", settings))


        for (int i = 0; i < 100; ++i)
            writer.WriteElementString("item", "Book "+ (i+1).ToString());


    } // End Using writer 


And btw, the fastest way to read XML is XmlReader:

public static void ReadXML()
    using (System.Xml.XmlReader xmlReader = System.Xml.XmlReader.Create(""))
        while (xmlReader.Read())
            if ((xmlReader.NodeType == System.Xml.XmlNodeType.Element) && (xmlReader.Name == "Cube"))
                if (xmlReader.HasAttributes)
                    System.Console.WriteLine(xmlReader.GetAttribute("currency") + ": " + xmlReader.GetAttribute("rate"));

        } // Whend 

    } // End Using xmlReader


And the most convenient way to read XML is to just deserialize the XML into a class.
This also works for creating the serialization classes, btw.
You can generate the class from XML with Xml2CSharp:

Calling remove in foreach loop in Java

To safely remove from a collection while iterating over it you should use an Iterator.

For example:

List<String> names = ....
Iterator<String> i = names.iterator();
while (i.hasNext()) {
   String s =; // must be called before you can call i.remove()
   // Do something

From the Java Documentation :

The iterators returned by this class's iterator and listIterator methods are fail-fast: if the list is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove or add methods, the iterator will throw a ConcurrentModificationException. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.

Perhaps what is unclear to many novices is the fact that iterating over a list using the for/foreach constructs implicitly creates an iterator which is necessarily inaccessible. This info can be found here

Finding the second highest number in array

If you want to 2nd highest and highest number index in array then....

public class Scoller_student {

    public static void main(String[] args) {
        System.out.println("\t\t\tEnter No. of Student\n");
        Scanner scan = new Scanner(;
        int student_no = scan.nextInt();

        // Marks Array.........
        int[] marks;
        marks = new int[student_no];

        // Student name array.....
        String[] names;
        names = new String[student_no];
        int max = 0;
        int sec = max;
        for (int i = 0; i < student_no; i++) {
            System.out.println("\t\t\tEnter Student Name of id = " + i + ".");

            names[i] =;
            System.out.println("\t\t\tEnter Student Score of id = " + i + ".\n");

            marks[i] = scan.nextInt();
            if (marks[max] < marks[i]) {
                sec = max;
                max = i;
            } else if (marks[sec] < marks[i] && marks[max] != marks[i]) {
                sec = i;

        if (max == sec) {
            sec = 1;
            for (int i = 1; i < student_no; i++) {
                if (marks[sec] < marks[i]) {
                    sec = i;

        System.out.println("\t\t\tHigherst score id = \"" + max + "\" Name : \""
            + names[max] + "\" Max mark : \"" + marks[max] + "\".\n");
        System.out.println("\t\t\tSecond Higherst score id = \"" + sec + "\" Name : \""
            + names[sec] + "\" Max mark : \"" + marks[sec] + "\".\n");


How to set iPhone UIView z index?

You can use the zPosition property of the view's layer (it's a CALayer object) to change the z-index of the view.

theView.layer.zPosition = 1;

As Viktor Nordling added, "big values are on top. You can use any values you want, including negative values." The default value is 0.

You need to import the QuartzCore framework to access the layer. Just add this line of code at the top of your implementation file.

#import "QuartzCore/QuartzCore.h"

How to set an HTTP proxy in Python 2.7?

cd C:\Python34\Scripts



pip.exe install PackageName

How to check visibility of software keyboard in Android?

You can observe softkeyboard's hide by using activity's decorView.

public final class SoftKeyboardUtil {
    public static final String TAG = "SoftKeyboardUtil";
    public static void observeSoftKeyBoard(Activity activity , final OnSoftKeyBoardHideListener listener){
        final View decorView = activity.getWindow().getDecorView();
        decorView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            public void onGlobalLayout() {
                Rect rect = new Rect();
                int displayHight = rect.bottom -;
                int hight = decorView.getHeight();
                boolean hide = (double)displayHight / hight > 0.8 ;
                if(Log.isLoggable(TAG, Log.DEBUG)){
                    Log.d(TAG ,"DecorView display hight = "+displayHight);
                    Log.d(TAG ,"DecorView hight = "+ hight);
                    Log.d(TAG, "softkeyboard visible = " + !hide);



    public interface OnSoftKeyBoardHideListener{
        void onSoftKeyBoardVisible(boolean visible);

Iterate through a HashMap

Extracted from the reference How to Iterate Over a Map in Java:

There are several ways of iterating over a Map in Java. Let's go over the most common methods and review their advantages and disadvantages. Since all maps in Java implement the Map interface, the following techniques will work for any map implementation (HashMap, TreeMap, LinkedHashMap, Hashtable, etc.)

Method #1: Iterating over entries using a For-Each loop.

This is the most common method and is preferable in most cases. It should be used if you need both map keys and values in the loop.

Map<Integer, Integer> map = new HashMap<Integer, Integer>();
for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());

Note that the For-Each loop was introduced in Java 5, so this method is working only in newer versions of the language. Also a For-Each loop will throw NullPointerException if you try to iterate over a map that is null, so before iterating you should always check for null references.

Method #2: Iterating over keys or values using a For-Each loop.

If you need only keys or values from the map, you can iterate over keySet or values instead of entrySet.

Map<Integer, Integer> map = new HashMap<Integer, Integer>();

// Iterating over keys only
for (Integer key : map.keySet()) {
    System.out.println("Key = " + key);

// Iterating over values only
for (Integer value : map.values()) {
    System.out.println("Value = " + value);

This method gives a slight performance advantage over entrySet iteration (about 10% faster) and is more clean.

Method #3: Iterating using Iterator.

Using Generics:

Map<Integer, Integer> map = new HashMap<Integer, Integer>();
Iterator<Map.Entry<Integer, Integer>> entries = map.entrySet().iterator();
while (entries.hasNext()) {
    Map.Entry<Integer, Integer> entry =;
    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());

Without Generics:

Map map = new HashMap();
Iterator entries = map.entrySet().iterator();
while (entries.hasNext()) {
    Map.Entry entry = (Map.Entry);
    Integer key = (Integer)entry.getKey();
    Integer value = (Integer)entry.getValue();
    System.out.println("Key = " + key + ", Value = " + value);

You can also use same technique to iterate over keySet or values.

This method might look redundant, but it has its own advantages. First of all, it is the only way to iterate over a map in older versions of Java. The other important feature is that it is the only method that allows you to remove entries from the map during iteration by calling iterator.remove(). If you try to do this during For-Each iteration you will get "unpredictable results" according to Javadoc.

From a performance point of view this method is equal to a For-Each iteration.

Method #4: Iterating over keys and searching for values (inefficient).

Map<Integer, Integer> map = new HashMap<Integer, Integer>();
for (Integer key : map.keySet()) {
    Integer value = map.get(key);
    System.out.println("Key = " + key + ", Value = " + value);

This might look like a cleaner alternative for method #1, but in practice it is pretty slow and inefficient as getting values by a key might be time-consuming (this method in different Map implementations is 20%-200% slower than method #1). If you have FindBugs installed, it will detect this and warn you about inefficient iteration. This method should be avoided.


If you need only keys or values from the map, use method #2. If you are stuck with older version of Java (less than 5) or planning to remove entries during iteration, you have to use method #3. Otherwise use method #1.

What's the difference between StaticResource and DynamicResource in WPF?

Important benefit of the dynamic resources

if application startup takes extremely long time, you must use dynamic resources, because static resources are always loaded when the window or app is created, while dynamic resources are loaded when they’re first used.

However, you won’t see any benefit unless your resource is extremely large and complex.

Swap DIV position with CSS only

This solution worked for me:

Using a parent element like:

.parent-div {
    flex-direction: column-reverse;

In my case I didn't have to change the css of the elements that I needed to switch.

Get index of clicked element in collection with jQuery


$(this).index() can be used to get the index of the clicked element if the elements are siblings.

<div id="container">
    <a href="#" class="link">1</a>
    <a href="#" class="link">2</a>
    <a href="#" class="link">3</a>
    <a href="#" class="link">4</a>

$('#container').on('click', 'a', function() {
<script src=""></script>
<div id="container">
  <a href="#" class="link">1</a>
  <a href="#" class="link">2</a>
  <a href="#" class="link">3</a>
  <a href="#" class="link">4</a>

Not siblings

If no argument is passed to the .index() method, the return value is an integer indicating the position of the first element within the jQuery object relative to its sibling elements.

Pass the selector to the index(selector).



Find the index of the <a> element that is clicked.

    <td><a href="#" class="adwa">0001</a></td>
    <td><a href="#" class="adwa">0002</a></td>
    <td><a href="#" class="adwa">0003</a></td>
    <td><a href="#" class="adwa">0004</a></td>


$('#table').on('click', '.adwa', function() {
<script src=""></script>
<table id="table">
            <th>vendor id</th>
            <td><a href="#" class="adwa">0001</a></td>
            <td><a href="#" class="adwa">0002</a></td>
            <td><a href="#" class="adwa">0003</a></td>
            <td><a href="#" class="adwa">0004</a></td>

How to navigate a few folders up?

The following method searches a file beginning with the application startup path (*.exe folder). If the file is not found there, the parent folders are searched until either the file is found or the root folder has been reached. null is returned if the file was not found.

public static FileInfo FindApplicationFile(string fileName)
    string startPath = Path.Combine(Application.StartupPath, fileName);
    FileInfo file = new FileInfo(startPath);
    while (!file.Exists) {
        if (file.Directory.Parent == null) {
            return null;
        DirectoryInfo parentDir = file.Directory.Parent;
        file = new FileInfo(Path.Combine(parentDir.FullName, file.Name));
    return file;

Note: Application.StartupPath is usually used in WinForms applications, but it works in console applications as well; however, you will have to set a reference to the System.Windows.Forms assembly. You can replace Application.StartupPath by
Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location) if you prefer.

Why calling react setState method doesn't mutate the state immediately?

From React's documentation:

setState() does not immediately mutate this.state but creates a pending state transition. Accessing this.state after calling this method can potentially return the existing value. There is no guarantee of synchronous operation of calls to setState and calls may be batched for performance gains.

If you want a function to be executed after the state change occurs, pass it in as a callback.

this.setState({value:}, function () {


There's no need for "else" in this case:

IF EXISTS(SELECT *  FROM  table1  WHERE Name='John' ) return 1
return 0

What does 'stale file handle' in Linux mean?

When the directory is deleted, the inode for that directory (and the inodes for its contents) are recycled. The pointer your shell has to that directory's inode (and its contents's inodes) are now no longer valid. When the directory is restored from backup, the old inodes are not (necessarily) reused; the directory and its contents are stored on random inodes. The only thing that stays the same is that the parent directory reuses the same name for the restored directory (because you told it to).

Now if you attempt to access the contents of the directory that your original shell is still pointing to, it communicates that request to the file system as a request for the original inode, which has since been recycled (and may even be in use for something entirely different now). So you get a stale file handle message because you asked for some nonexistent data.

When you perform a cd operation, the shell reevaluates the inode location of whatever destination you give it. Now that your shell knows the new inode for the directory (and the new inodes for its contents), future requests for its contents will be valid.

Resetting a multi-stage form with jQuery

I normally add a hidden reset button to the form. when needed just: $('#reset').click();

Binding a Button's visibility to a bool value in ViewModel

There's a third way that doesn't require a converter or a change to your view model: use a style:

<Style TargetType="Button">
   <Setter Property="Visibility" Value="Collapsed"/>
      <DataTrigger Binding="{Binding IsVisible}" Value="True">
         <Setter Property="Visibility" Value="Visible"/>

I tend to prefer this technique because I use it in a lot of cases where what I'm binding to is not boolean - e.g. displaying an element only if its DataContext is not null, or implementing multi-state displays where different layouts appear based on the setting of an enum in the view model.

"Notice: Undefined variable", "Notice: Undefined index", and "Notice: Undefined offset" using PHP

In PHP 7.0 it's now possible to use Null coalescing operator:

echo "My index value is: " . ($my_array["my_index"] ?? '');

Equals to:

echo "My index value is: " . (isset($my_array["my_index"]) ? $my_array["my_index"] : '');

PHP manual PHP 7.0

Java: splitting a comma-separated string but ignoring commas in quotes

Rather than use lookahead and other crazy regex, just pull out the quotes first. That is, for every quote grouping, replace that grouping with __IDENTIFIER_1 or some other indicator, and map that grouping to a map of string,string.

After you split on comma, replace all mapped identifiers with the original string values.

Make the size of a heatmap bigger with seaborn

add plt.figure(figsize=(16,5)) before the sns.heatmap and play around with the figsize numbers till you get the desired size


plt.figure(figsize = (16,5))

ax = sns.heatmap(df1.iloc[:, 1:6:], annot=True, linewidths=.5)

Java switch statement: Constant expression required, but it IS constant

Below code is self-explanatory, We can use an enum with a switch case:

enum ClassNames {
    STRING(String.class, String.class.getSimpleName()),
    BOOLEAN(Boolean.class, Boolean.class.getSimpleName()),
    INTEGER(Integer.class, Integer.class.getSimpleName()),
    LONG(Long.class, Long.class.getSimpleName());
    private Class typeName;
    private String simpleName;
    ClassNames(Class typeName, String simpleName){
        this.typeName = typeName;
        this.simpleName = simpleName;

Based on the class values from the enum can be mapped:

 switch (ClassNames.valueOf(clazz.getSimpleName())) {
        case STRING:
            String castValue = (String) keyValue;
        case BOOLEAN:
        case Integer:
        case LONG:
            isValid = false;


Hope it helps :)

Can I dispatch an action in reducer?

Dispatching an action within a reducer is an anti-pattern. Your reducer should be without side effects, simply digesting the action payload and returning a new state object. Adding listeners and dispatching actions within the reducer can lead to chained actions and other side effects.

Sounds like your initialized AudioElement class and the event listener belong within a component rather than in state. Within the event listener you can dispatch an action, which will update progress in state.

You can either initialize the AudioElement class object in a new React component or just convert that class to a React component.

class MyAudioPlayer extends React.Component {
  constructor(props) {

    this.player = new AudioElement('test.mp3'); = this.updateProgress;

  updateProgress () {
    // Dispatch action to reducer with updated progress.
    // You might want to actually send the current time and do the
    // calculation from within the reducer.

  render () {
    // Render the audio player controls, progress bar, whatever else
    return <p>Progress: {this.props.progress}</p>;

class MyContainer extends React.Component {
   render() {
     return <MyAudioPlayer updateProgress={this.props.updateProgress} />

function mapStateToProps (state) { return {}; }

return connect(mapStateToProps, {

Note that the updateProgressAction is automatically wrapped with dispatch so you don't need to call dispatch directly.

Maven error in eclipse (pom.xml) : Failure to transfer org.apache.maven.plugins:maven-surefire-plugin:pom:2.12.4

If you are using Eclipse Neon, try this:

1) Add the maven plugin in the properties section of the POM:


2) Force update of project snapshot by right clicking on Project

Maven -> Update Project -> Select your Project -> Tick on the 'Force Update of Snapshots/Releases' option -> OK

Autowiring two beans implementing same interface - how to set default bean to autowire?

For Spring 2.5, there's no @Primary. The only way is to use @Qualifier.

Mysql command not found in OS X 10.7

One alternative way is creating soft link in /usr/local/bin

ln -s /usr/local/mysql/bin/mysql /usr/local/bin/mysql

But if you need other executables like mysqldump, you will need to create soft link for them.

Android Gradle plugin 0.7.0: "duplicate files during packaging of APK"

  packagingOptions {
    exclude 'META-INF/DEPENDENCIES.txt'
    exclude 'META-INF/dependencies.txt'
    exclude 'META-INF/LICENSE.txt'
    exclude 'META-INF/LICENSE'
    exclude 'META-INF/license.txt'
    exclude 'META-INF/LGPL2.1'
    exclude 'META-INF/NOTICE.txt'
    exclude 'META-INF/NOTICE'
    exclude 'META-INF/notice.txt'

Difference between Method and Function?

Both are same, there is no difference its just a different term for the same thing in C#.


In object-oriented programming, a method is a subroutine (or procedure or function) associated with a class.

With respect to Object Oriented programming the term "Method" is used, not functions.

Reset input value in angular 2

Working with Angular 7 I needed to create a file upload with a description of the file.


File Description: <input type="text" (change)="updateFileDescription($" #fileDescription />

<input type="file" accept="*" capture (change)="handleFileInput($" #fileInput /> <button class="btn btn-light" (click)="uploadFileToActivity()">Upload</button>

Here is the Component file

  @ViewChild('fileDescription') fileDescriptionInput: ElementRef;
  @ViewChild('fileInput') fileInput: ElementRef;

        this.fileDescriptionInput.nativeElement.value = '';
        this.fileInput.nativeElement.value = '';

This will do the trick.

VT-x is disabled in the BIOS for both all CPU modes (VERR_VMX_MSR_ALL_VMX_DISABLED)

In Virtual Box "Settings" > System Settings > Processor > Enable the PAE/NX option. It resolved my issue.

How to change the URL from "localhost" to something else, on a local system using wampserver?

WINDOWS + WAMP solution

Step 1
Go to C:\wamp\bin\apache\Apache2.2.17\conf\
open httpd.conf file and change
#Include conf/extra/httpd-vhosts.conf
Include conf/extra/httpd-vhosts.conf
i.e. uncomment the line so that it can includes the virtual hosts file.

Step 2
Go to C:\wamp\bin\apache\Apache2.2.17\conf\extra
and open httpd-vhosts.conf file and add the following code

<VirtualHost myWebsite.local>
    DocumentRoot "C:/wamp/www/myWebsite/"
    ServerName myWebsite.local
    ServerAlias myWebsite.local
    <Directory "C:/wamp/www/myWebsite/">
        Order allow,deny
        Allow from all

change myWebsite.local and C:/wamp/www/myWebsite/ as per your requirements.

Step 3
Open hosts file in C:/Windows/System32/drivers/etc/ and add the following line ( Don't delete anything ) myWebsite.local

change myWebsite.local as per your name requirements

Step 4
restart your server. That's it

WINDOWS + XAMPP solution

Same steps as that of WAMP just change the paths according to XAMPP which corresponds to path in WAMP

How do I write a RGB color value in JavaScript?

Here's a simple function that creates a CSS color string from RGB values ranging from 0 to 255:

function rgb(r, g, b){
  return "rgb("+r+","+g+","+b+")";

Alternatively (to create fewer string objects), you could use array join():

function rgb(r, g, b){
  return ["rgb(",r,",",g,",",b,")"].join("");

The above functions will only work properly if (r, g, and b) are integers between 0 and 255. If they are not integers, the color system will treat them as in the range from 0 to 1. To account for non-integer numbers, use the following:

function rgb(r, g, b){
  r = Math.floor(r);
  g = Math.floor(g);
  b = Math.floor(b);
  return ["rgb(",r,",",g,",",b,")"].join("");

You could also use ES6 language features:

const rgb = (r, g, b) => 

How to detect a textbox's content has changed

I'd like to ask why you are trying to detect when the content of the textbox changed in real time?

An alternative would be to set a timer (via setIntval?) and compare last saved value to the current one and then reset a timer. This would guarantee catching ANY change, whether caused by keys, mouse, some other input device you didn't consider, or even JavaScript changing the value (another possiblity nobody mentioned) from a different part of the app.

How can I drop all the tables in a PostgreSQL database?

The easiest way is to drop the public schema as others have suggested in previous answers. However, this is NOT a good way. You never know what has been done to the public schema that has since been forgotten and was not documented. You also don't know if this will work the same into the future. In V9, it would have been fine, but in V10 all your users would loose access to the schema, and must be granted access again otherwise your application will break. I haven't checked V11, but the point is that you never know what will break as you move from machine to machine, site to site or version to version. It also cannot be done if you are a user that has access to the database, but not to the schema.

If you need to do this programmatically then other answers above cover this, but one thing the answers above don't consider is to get Postgres to do the work for you. If you use pg_dump with the -c option as below:

sudo su postgres -c "pg_dump -U postgres WhateverDB -c -f "/home/Anyone/DBBackupWhateverDB-ServerUnscheduled.sql""

That will create a DB restore script with sql statements that will delete all the tables.

If the only purpose in asking the question was to delete the tables prior to restore, then your restore will do the work for you.

However, if you need it for something else, you can simply copy the drop statements from the sql script.

Show constraints on tables command

There is also a tool that oracle made called mysqlshow

If you run it with the --k keys $table_name option it will display the keys.

   mysqlshow [options] [db_name [tbl_name [col_name]]]
·   --keys, -k
   Show table indexes.


?-?  mysqlshow -h -u root -p --keys database tokens
Database: database  Table: tokens
| Field           | Type             | Collation          | Null | Key | Default | Extra          | Privileges                      | Comment |
| id              | int(10) unsigned |                    | NO   | PRI |         | auto_increment | select,insert,update,references |         |
| token           | text             | utf8mb4_unicode_ci | NO   |     |         |                | select,insert,update,references |         |
| user_id         | int(10) unsigned |                    | NO   | MUL |         |                | select,insert,update,references |         |
| expires_in      | datetime         |                    | YES  |     |         |                | select,insert,update,references |         |
| created_at      | timestamp        |                    | YES  |     |         |                | select,insert,update,references |         |
| updated_at      | timestamp        |                    | YES  |     |         |                | select,insert,update,references |         |
| Table  | Non_unique | Key_name                 | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
| tokens | 0          | PRIMARY                  | 1            | id          | A         | 2           |          |        |      | BTREE      |         |               |
| tokens | 1          | tokens_user_id_foreign   | 1            | user_id     | A         | 2           |          |        |      | BTREE      |         |               |

How do I convert two lists into a dictionary?

For those who need simple code and aren’t familiar with zip:

List1 = ['This', 'is', 'a', 'list']
List2 = ['Put', 'this', 'into', 'dictionary']

This can be done by one line of code:

d = {List1[n]: List2[n] for n in range(len(List1))}

Launch iOS simulator from Xcode and getting a black screen, followed by Xcode hanging and unable to stop tasks

This could result from not setting the correct deployment info. (i.e. if your storyboard isn't set as the main interface)

How to get a view table query (code) in SQL Server 2008 Management Studio

Additionally, if you have restricted access to the database (IE: Can't use "Script Function as > CREATE To"), there is another option to get this query.

Find your View > right click > "Design".

This will give you the query you are looking for.

What's the easy way to auto create non existing dir in ansible

AFAIK, the only way this could be done is by using the state=directory option. While template module supports most of copy options, which in turn supports most file options, you can not use something like state=directory with it. Moreover, it would be quite confusing (would it mean that {{project_root}}/conf/code.conf is a directory ? or would it mean that {{project_root}}/conf/ should be created first.

So I don't think this is possible right now without adding a previous file task.

- file: 
    path: "{{project_root}}/conf"
    state: directory
    recurse: yes

How to ignore the certificate check when ssl

Tip: You can also use this method to track certificates that are due to expire soon. This can save your bacon if you discover a cert that is about to expire and can get it fixed in time. Good also for third party companies - for us this is DHL / FedEx. DHL just let a cert expire which is screwing us up 3 days before Thanksgiving. Fortunately I'm around to fix it ... this time!

    private static DateTime? _nextCertWarning;
    private static bool ValidateRemoteCertificate(object sender, X509Certificate cert, X509Chain chain, SslPolicyErrors error)
        if (error == SslPolicyErrors.None)
            var cert2 = cert as X509Certificate2;
            if (cert2 != null)
                // If cert expires within 2 days send an alert every 2 hours
                if (cert2.NotAfter.AddDays(-2) < DateTime.Now)
                    if (_nextCertWarning == null || _nextCertWarning < DateTime.Now)
                        _nextCertWarning = DateTime.Now.AddHours(2);

                        ProwlUtil.StepReached("CERT EXPIRING WITHIN 2 DAYS " + cert, cert.GetCertHashString());   // this is my own function

            return true;
            switch (cert.GetCertHashString())
                // Machine certs - SELF SIGNED
                case "066CF9CAD814DE2097D367F22D3A7E398B87C4D6":    

                    return true;

                    ProwlUtil.StepReached("UNTRUSTED CERT " + cert, cert.GetCertHashString());
                    return false;

What's the better (cleaner) way to ignore output in PowerShell?

I would consider using something like:

function GetList
  . {
     $a = new-object Collections.ArrayList
     $a.Add('next 5')
  } | Out-Null
$x = GetList

Output from $a.Add is not returned -- that holds for all $a.Add method calls. Otherwise you would need to prepend [void] before each the call.

In simple cases I would go with [void]$a.Add because it is quite clear that output will not be used and is discarded.

Less aggressive compilation with CSS3 calc

A very common usecase of calc is take 100% width and adding some margin around the element.

One can do so with:

@someMarginVariable = 15px;

margin: @someMarginVariable;
width: calc(~"100% - "@someMarginVariable*2);
width: -moz-calc(~"100% - "@someMarginVariable*2);
width: -webkit-calc(~"100% - "@someMarginVariable*2);

How do I check/uncheck all checkboxes with a button using jQuery?

Try this one :

        $(this).val('uncheck all');
        $(this).val('check all');        


What is the difference between require and require-dev sections in composer.json?

Different Environments

Typically, software will run in different environments:

  • development
  • testing
  • staging
  • production

Different Dependencies in Different Environments

The dependencies which are declared in the require section of composer.json are typically dependencies which are required for running an application or a package in

  • staging
  • production

environments, whereas the dependencies declared in the require-dev section are typically dependencies which are required in

  • developing
  • testing


For example, in addition to the packages used for actually running an application, packages might be needed for developing the software, such as:

  • friendsofphp/php-cs-fixer (to detect and fix coding style issues)
  • squizlabs/php_codesniffer (to detect and fix coding style issues)
  • phpunit/phpunit (to drive the development using tests)
  • etc.


Now, in development and testing environments, you would typically run

$ composer install

to install both production and development dependencies.

However, in staging and production environments, you only want to install dependencies which are required for running the application, and as part of the deployment process, you would typically run

$ composer install --no-dev

to install only production dependencies.


In other words, the sections

  • require
  • require-dev

indicate to composer which packages should be installed when you run

$ composer install


$ composer install --no-dev

That is all.

Note Development dependencies of packages your application or package depend on will never be installed

For reference, see:

Dynamic Height Issue for UITableView Cells (Swift)

Set automatic dimension for row height & estimated row height and ensure following steps:

@IBOutlet weak var table: UITableView!

override func viewDidLoad() {

    // Set automatic dimensions for row height
    // Swift 4.2 onwards
    table.rowHeight = UITableView.automaticDimension
    table.estimatedRowHeight = UITableView.automaticDimension

    // Swift 4.1 and below
    table.rowHeight = UITableViewAutomaticDimension
    table.estimatedRowHeight = UITableViewAutomaticDimension


// UITableViewAutomaticDimension calculates height of label contents/text
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
    // Swift 4.2 onwards
    return UITableView.automaticDimension

    // Swift 4.1 and below
    return UITableViewAutomaticDimension

For Example: if you have a label in your UITableviewCell then,

  • Set number of lines = 0 (& line break mode = truncate tail)
  • Set all constraints (top, bottom, right left) with respect to its superview/ cell container.
  • Optional: Set minimum height for label, if you want minimum vertical area covered by label, even if there is no data.

Here is sample label with dynamic height constraints.

enter image description here

Is there a way to cast float as a decimal without rounding and preserving its precision?

Have you tried:

SELECT Cast( 2.555 as decimal(53,8))

This would return 2.55500000. Is that what you want?


Apparently you can also use SQL_VARIANT_PROPERTY to find the precision and scale of a value. Example:

SELECT SQL_VARIANT_PROPERTY(Cast( 2.555 as decimal(8,7)),'Precision'),
SQL_VARIANT_PROPERTY(Cast( 2.555 as decimal(8,7)),'Scale')

returns 8|7

You may be able to use this in your conversion process...

How can I get the value of a registry key from within a batch script?

set regVar_LocalPrjPath="LocalPrjPath"
set regVar_Path="HKEY_CURRENT_USER\Software\xyz\KeyPath"

:: ### Retrieve VAR1 ###
FOR /F "skip=2 tokens=2,*" %%A IN ('reg.exe query %regVar_Path% /v %regVar_LocalPrjPath%') DO set "VAR1=%%B"

What does DIM stand for in Visual Basic and BASIC?

Variable declaration. Initially, it was short for "dimension", which is not a term that is used in programming (outside of this specific keyword) to any significant degree.

How do I disable directory browsing?

Apart from the aformentioned two methods (edit /etc/apache2/apache2.conf or add Options -Indexes in .htaccess file), here is another one

a2dismod autoindex

Restart the apache2 server afterwards

sudo service apache2 restart

Entity Framework : How do you refresh the model when the db changes?

Update CodeFirst Model is not possible automatically. I don't recommend either. Because one of the benefits of code first is you can work with POCO classes. If you changed this POCO classes you don't want some auto generated code to destroy your work.

But you can create some template solution add your updated/added entity to the new model. then collect and move your new cs file to your working project. this way you will not have a conflict if it is a new entity you can simply adding related cs file to the existing project. if it is an update just add a new property from the file. If you just adding some couple of columns to one or two of your tables you can manually add them to your POCO class you don't need any extra works and that is the beauty of Working with Code-First and POCO classes.

How do I make a C++ macro behave like a function?

There is a rather clever solution:

#define MACRO(X,Y)                         \
do {                                       \
  cout << "1st arg is:" << (X) << endl;    \
  cout << "2nd arg is:" << (Y) << endl;    \
  cout << "Sum is:" << ((X)+(Y)) << endl;  \
} while (0)

Now you have a single block-level statement, which must be followed by a semicolon. This behaves as expected and desired in all three examples.

How to post data to specific URL using WebClient in C#

Here is the crisp answer:

public String sendSMS(String phone, String token) {
    WebClient webClient = WebClient.create(smsServiceUrl);

    SMSRequest smsRequest = new SMSRequest();

    Mono<String> response =
          .header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
          .body(Mono.just(smsRequest), SMSRequest.class)

    String deliveryResponse = response.block();
    if (deliveryResponse.equalsIgnoreCase("success")) {
      return deliveryResponse;
    return null;

jQuery 'input' event

$("input#myId").bind('keyup', function (e) {    
    // Do Stuff

working in both IE and chrome

Ping site and return result in PHP

Another option (if you need/want to ping instead of send an HTTP request) is the Ping class for PHP. I wrote it for just this purpose, and it lets you use one of three supported methods to ping a server (some servers/environments only support one of the three methods).

Example usage:

$host = '';
$ping = new Ping($host);
$latency = $ping->ping();
if ($latency) {
  print 'Latency is ' . $latency . ' ms';
else {
  print 'Host could not be reached.';

Values of disabled inputs will not be submitted

Yes, all browsers should not submit the disabled inputs, as they are read-only.

More information (section 17.12.1)

Attribute definitions

disabled [CI] When set for a form control, this Boolean attribute disables the control for user input. When set, the disabled attribute has the following effects on an element:

  • Disabled controls do not receive focus.
  • Disabled controls are skipped in tabbing navigation.
  • Disabled controls cannot be successful.

The following elements support the disabled attribute: BUTTON, INPUT, OPTGROUP, OPTION, SELECT, and TEXTAREA.

This attribute is inherited but local declarations override the inherited value.

How disabled elements are rendered depends on the user agent. For example, some user agents "gray out" disabled menu items, button labels, etc.

In this example, the INPUT element is disabled. Therefore, it cannot receive user input nor will its value be submitted with the form.

<INPUT disabled name="fred" value="stone">

Note. The only way to modify dynamically the value of the disabled attribute is through a script.

Magento Product Attribute Get Value

Try this

 $attribute = $_product->getResource()->getAttribute('custom_attribute_code');
    if ($attribute)
        echo $attribute_value = $attribute ->getFrontend()->getValue($_product);

How to remove a key from Hash and get the remaining hash in Ruby/Rails?

Oneliner plain ruby, it works only with ruby > 1.9.x:

1.9.3p0 :002 > h = {:a => 1, :b => 2}
 => {:a=>1, :b=>2} 
1.9.3p0 :003 > h.tap { |hs| hs.delete(:a) }
 => {:b=>2} 

Tap method always return the object on which is invoked...

Otherwise if you have required active_support/core_ext/hash (which is automatically required in every Rails application) you can use one of the following methods depending on your needs:

?  ~  irb
1.9.3p125 :001 > require 'active_support/core_ext/hash' => true 
1.9.3p125 :002 > h = {:a => 1, :b => 2, :c => 3}
 => {:a=>1, :b=>2, :c=>3} 
1.9.3p125 :003 > h.except(:a)
 => {:b=>2, :c=>3} 
1.9.3p125 :004 > h.slice(:a)
 => {:a=>1} 

except uses a blacklist approach, so it removes all the keys listed as args, while slice uses a whitelist approach, so it removes all keys that aren't listed as arguments. There also exist the bang version of those method (except! and slice!) which modify the given hash but their return value is different both of them return an hash. It represents the removed keys for slice! and the keys that are kept for the except!:

1.9.3p125 :011 > {:a => 1, :b => 2, :c => 3}.except!(:a)
 => {:b=>2, :c=>3} 
1.9.3p125 :012 > {:a => 1, :b => 2, :c => 3}.slice!(:a)
 => {:b=>2, :c=>3} 

How do I configure modprobe to find my module?

You can make a symbolic link of your module to the standard path, so depmod will see it and you'll be able load it as any other module.

sudo ln -s /path/to/module.ko /lib/modules/`uname -r`
sudo depmod -a
sudo modprobe module

If you add the module name to /etc/modules it will be loaded any time you boot.

Anyway I think that the proper configuration is to copy the module to the standard paths.

Extract filename and extension in Bash

~% FILE="example.tar.gz"

~% echo "${FILE%%.*}"

~% echo "${FILE%.*}"

~% echo "${FILE#*.}"

~% echo "${FILE##*.}"

For more details, see shell parameter expansion in the Bash manual.

Convenient way to parse incoming multipart/form-data parameters in a Servlet


Solution A:

  1. Download
  2. Invoke getParameters() on com.oreilly.servlet.MultipartRequest

Solution B:

  1. Download
  2. Invoke readHeaders() in org.apache.commons.fileupload.MultipartStream

Solution C:

  1. Download
  2. Invoke getParameter on com.bigfoot.bugar.servlet.http.MultipartFormData

Solution D:

Use Struts. Struts 1.1 handles this automatically.


center aligning a fixed position div

Koen's answer doesn't exactly centers the element.

The proper way is to use CCS3 transform property. Although it's not supported in some old browsers. And we don't even need to set a fixed or relative width.

.centered {
    position: fixed;
    left: 50%;
    transform: translate(-50%, 0);

Working jsfiddle comparison here.

Writing a string to a cell in excel

try this instead

Set TxtRng = ActiveWorkbook.Sheets("Game").Range("A1")


Maybe the file is corrupt - this has happened to me several times before and the only solution is to copy everything out into a new file.

Please can you try the following:

  • Save a new xlsm file and call it "MyFullyQualified.xlsm"
  • Add a sheet with no protection and call it "mySheet"
  • Add a module to the workbook and add the following procedure

Does this run?

 Sub varchanger()

 With Excel.Application
    .ScreenUpdating = True
    .Calculation = Excel.xlCalculationAutomatic
    .EnableEvents = True
 End With

 On Error GoTo Whoa:

    Dim myBook As Excel.Workbook
    Dim mySheet As Excel.Worksheet
    Dim Rng  As Excel.Range

    Set myBook = Excel.Workbooks("MyFullyQualified.xlsm")
    Set mySheet = myBook.Worksheets("mySheet")
    Set Rng = mySheet.Range("A1")


    Rng.Value = "SubTotal"

    Excel.Workbooks("MyFullyQualified.xlsm").Worksheets("mySheet").Range("A1").Value = "Asdf"

        Exit Sub
        MsgBox Err.Number
        GoTo LetsContinue

End Sub

How do I reference to another (open or closed) workbook, and pull values back, in VBA? - Excel 2007

You will have to open the file in one way or another if you want to access the data within it. Obviously, one way is to open it in your Excel application instance, e.g.:-

(untested code)

Dim wbk As Workbook
Set wbk = Workbooks.Open("C:\myworkbook.xls")

' now you can manipulate the data in the workbook anyway you want, e.g. '

Dim x As Variant
x = wbk.Worksheets("Sheet1").Range("A6").Value

Call wbk.Worksheets("Sheet2").Range("A1:G100").Copy
Call ThisWorbook.Worksheets("Target").Range("A1").PasteSpecial(xlPasteValues)
Application.CutCopyMode = False

' etc '

Call wbk.Close(False)

Another way to do it would be to use the Excel ADODB provider to open a connection to the file and then use SQL to select data from the sheet you want, but since you are anyway working from within Excel I don't believe there is any reason to do this rather than just open the workbook. Note that there are optional parameters for the Workbooks.Open() method to open the workbook as read-only, etc.

How can I clear the Scanner buffer in Java?

Try this:


This advances the Scanner to the next line.

Check whether a string is not null and not empty

Use Apache StringUtils' isNotBlank method like


It will return true only if the str is not null and is not empty.

Best way to Bulk Insert from a C# DataTable

This is going to be largely dependent on the RDBMS you're using, and whether a .NET option even exists for that RDBMS.

If you're using SQL Server, use the SqlBulkCopy class.

For other database vendors, try googling for them specifically. For example a search for ".NET Bulk insert into Oracle" turned up some interesting results, including this link back to Stack Overflow: Bulk Insert to Oracle using .NET.

Split string based on regex

I suggest

l = re.compile("(?<!^)\s+(?=[A-Z])(?!.\s)").split(s)

Check this demo.

jQuery multiselect drop down menu

You could hack your own, not relying on jQuery plugins... though you'd need to keep track externally (in JS) of selected items since the transition would remove the selected state info:

  <script type='text/javascript' src=''></script>
  <script type='text/javascript'>
        $('#transactionType').attr('multiple', true);
        $('#transactionType').attr('multiple', false);
  <select id="transactionType">
    <option value="ALLOC">ALLOC</option>
    <option value="LOAD1">LOAD1</option>
    <option value="LOAD2">LOAD2</option>

How do I send an HTML Form in an Email .. not just MAILTO

I actually use ASP C# to send my emails now, with something that looks like :

protected void Page_Load(object sender, EventArgs e)
    if (Request.Form.Count > 0)
        string formEmail = "";
        string fromEmail = "[email protected]";
        string defaultEmail = "[email protected]";

        string sendTo1 = "";

        int x = 0;

        for (int i = 0; i < Request.Form.Keys.Count; i++)
            formEmail += "<strong>" + Request.Form.Keys[i] + "</strong>";
            formEmail += ": " + Request.Form[i] + "<br/>";
            if (Request.Form.Keys[i] == "Email")
                if (Request.Form[i].ToString() != string.Empty)
                    fromEmail = Request.Form[i].ToString();
                formEmail += "<br/>";

        System.Net.Mail.MailMessage myMsg = new System.Net.Mail.MailMessage();
        SmtpClient smtpClient = new SmtpClient();

            myMsg.To.Add(new System.Net.Mail.MailAddress(defaultEmail));
            myMsg.IsBodyHtml = true;
            myMsg.Body = formEmail;
            myMsg.From = new System.Net.Mail.MailAddress(fromEmail);
            myMsg.Subject = "Sent using Gmail Smtp";
            smtpClient.Host = "";
            smtpClient.Port = 587;
            smtpClient.EnableSsl = true;
            smtpClient.UseDefaultCredentials = true;
            smtpClient.Credentials = new System.Net.NetworkCredential("[email protected]", "pward");

            smtpClient.Send(defaultEmail, sendTo1, "Sent using gmail smpt", formEmail);

        catch (Exception ee)
            debug.Text += ee.Message;

This is an example using gmail as the smtp mail sender. Some of what is in here isn't needed, but it is how I use it, as I am sure there are more effective ways in the same fashion.

MongoDB: update every document on one field

This code will be helpful for you

            'type': "newuser"
        }, {
            $set: {
                email: "[email protected]",
        }, {
            multi: true
        function(err, result) {

angularjs directive call function specified in attribute and pass an argument to it

Marko's solution works well.

To contrast with recommended Angular way (as shown by treeface's plunkr) is to use a callback expression which does not require defining the expressionHandler. In marko's example change:

In template

<div my-method="theMethodToBeCalled(myParam)"></div>

In directive link function

$(element).click(function( e, rowid ) {
  scope.method({myParam: id});

This does have one disadvantage compared to marko's solution - on first load theMethodToBeCalled function will be invoked with myParam === undefined.

A working exampe can be found at @treeface Plunker

Volley JsonObjectRequest Post request not working

The override function getParams works fine. You use POST method and you have set the jBody as null. That's why it doesn't work. You could use GET method if you want to send null jBody. I have override the method getParams and it works either with GET method (and null jBody) either with POST method (and jBody != null)

Also there are all the examples here

how to make a countdown timer in java

import java.util.Scanner;
import java.util.Timer;
import java.util.TimerTask;

public class Stopwatch {
static int interval;
static Timer timer;

public static void main(String[] args) {
    Scanner sc = new Scanner(;
    System.out.print("Input seconds => : ");
    String secs = sc.nextLine();
    int delay = 1000;
    int period = 1000;
    timer = new Timer();
    interval = Integer.parseInt(secs);
    timer.scheduleAtFixedRate(new TimerTask() {

        public void run() {

    }, delay, period);

private static final int setInterval() {
    if (interval == 1)
    return --interval;

Try this.

ld cannot find -l<library>

I had a similar problem with another library and the reason why it didn't found it, was that I didn't run the make install (after running ./configure and make) for that library. The make install may require root privileges (in this case use: sudo make install). After running the make install you should have the so files in the correct folder, i.e. here /usr/local/lib and not in the folder mentioned by you.

Fastest way to write huge data in text file Java

You might try removing the BufferedWriter and just using the FileWriter directly. On a modern system there's a good chance you're just writing to the drive's cache memory anyway.

It takes me in the range of 4-5 seconds to write 175MB (4 million strings) -- this is on a dual-core 2.4GHz Dell running Windows XP with an 80GB, 7200-RPM Hitachi disk.

Can you isolate how much of the time is record retrieval and how much is file writing?

import java.util.ArrayList;
import java.util.List;

public class FileWritingPerfTest {

private static final int ITERATIONS = 5;
private static final double MEG = (Math.pow(1024, 2));
private static final int RECORD_COUNT = 4000000;
private static final String RECORD = "Help I am trapped in a fortune cookie factory\n";
private static final int RECSIZE = RECORD.getBytes().length;

public static void main(String[] args) throws Exception {
    List<String> records = new ArrayList<String>(RECORD_COUNT);
    int size = 0;
    for (int i = 0; i < RECORD_COUNT; i++) {
        size += RECSIZE;
    System.out.println(records.size() + " 'records'");
    System.out.println(size / MEG + " MB");
    for (int i = 0; i < ITERATIONS; i++) {
        System.out.println("\nIteration " + i);
        writeBuffered(records, 8192);
        writeBuffered(records, (int) MEG);
        writeBuffered(records, 4 * (int) MEG);

private static void writeRaw(List<String> records) throws IOException {
    File file = File.createTempFile("foo", ".txt");
    try {
        FileWriter writer = new FileWriter(file);
        System.out.print("Writing raw... ");
        write(records, writer);
    } finally {
        // comment this out if you want to inspect the files afterward

private static void writeBuffered(List<String> records, int bufSize) throws IOException {
    File file = File.createTempFile("foo", ".txt");
    try {
        FileWriter writer = new FileWriter(file);
        BufferedWriter bufferedWriter = new BufferedWriter(writer, bufSize);
        System.out.print("Writing buffered (buffer size: " + bufSize + ")... ");
        write(records, bufferedWriter);
    } finally {
        // comment this out if you want to inspect the files afterward

private static void write(List<String> records, Writer writer) throws IOException {
    long start = System.currentTimeMillis();
    for (String record: records) {
    // writer.flush(); // close() should take care of this
    long end = System.currentTimeMillis();
    System.out.println((end - start) / 1000f + " seconds");

wget command to download a file and save as a different filename

Also notice the order of parameters on the command line. At least on some systems (e.g. CentOS 6):

wget -O FILE URL

works. But:

wget URL -O FILE

does not work.

ADB No Devices Found

GoTo DeviceManager, then right click on the android device and click uninstall driver. Unplug and plug the device back...then a pop will come on your device while your pc installs the required drivers. Click "allow" on the popup. You can see your device when you type "adb devices" in command prompt.

How to set the title of UIButton as left alignment?


button.semanticContentAttribute = UISemanticContentAttributeForceRightToLeft;


You can solve this error by running cmd as admin than enter image description here

Do the same as in picture for windows 32 bit

Just make changes in 64 bit as framework64 instead of framework only Than go to iis and refresh the site
If u still got some error make changes in application pool

How to find server name of SQL Server Management Studio

Make sure you have installed SQL Server.

If not, follow this link and download.

Once SQL server is installed successfully. You will get server name. Refer to the below picture:

enter image description here

ASP.NET MVC View Engine Comparison

Check this SharpDOM . This is a c# 4.0 internal dsl for generating html and also mvc view engine.

Percentage width in a RelativeLayout

Interestingly enough, building on the answer from @olefevre, one can not only do 50/50 layouts with "invisible struts", but all sorts of layouts involving powers of two.

For example, here is a layout that cuts the width into four equal parts (actually three, with weights of 1, 1, 2):

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android=""
    android:layout_height="wrap_content" >

        android:background="#000000" />

        android:layout_toLeftOf="@+id/strut" >

            android:background="#000000" />

            android:text="Far Left" />

            android:text="Near Left" />

            android:text="Right" />


C# Change A Button's Background Color

In WPF, the background is not a Color, it is a Brush. So, try this for starters:

using System.Windows.Media;

// ....

ButtonToday.Background = new SolidColorBrush(Colors.Red);

More sensibly, though, you should probably look at doing this in your Xaml instead of in code.

How to call webmethod in C#

This is a bit late, but I just stumbled on this problem, trying to resolve my own problem of this kind. I then realized that I had this line in the ajax post wrong:

data: "{'quantity' : " + total_qty + ",'itemId':" + itemId + "}",

It should be:

data: "{quantity : '" + total_qty + "',itemId: '" + itemId + "'}",

As well as the WebMethod to:

public static string AddTo_Cart(string quantity, string itemId)

And this resolved my problem.

Hope it may be of help to someone else as well.

What is the difference between Sprint and Iteration in Scrum and length of each Sprint?

According to my experience

  1. Sprint is a kind of Iteration and one can have many Iterations within a single Sprint (e.g. one shall startover or iterate a task if it's failed and still having extra estimated time) or across many Sprints (such as performing ongoing tasks).
  2. Normally, the duration for a Sprint can be one or two weeks, It depends on the time required and the priority of tasks (which could be defined by Product Owner or Scrum Master or the team) from the Product Backlog.


Trigger standard HTML5 validation (form) without using submit button?

I think its simpler:

if (e.isValid())
//your code.

this will stop the submit until form is valid.

Type of expression is ambiguous without more context Swift

This can happen if any part of your highlighted method or property is attempting to access a property or method with the incorrect type.

Here is a troubleshooting checklist:

  • Make sure the type of arguments match in the call site and implementation.
  • Make sure the argument names match in the call site and implementation.
  • Make sure the method name matches in the call site and implementation.
  • Make sure the returned value of a property or method matches in the usage and implementation (ie: enumerated())
  • Make sure you don't have a duplicated method with potentially ambiguous types such as with protocols or generics.
  • Make sure the compiler can infer the correct type when using type inference.

A Strategy

  • Try breaking apart your method into a greater number of simpler method/implementations.

For example, lets say you are running compactMap on an array of custom Types. In the closure you are passing to the compactMap method, you initialize and return another custom struct. When you get this error, it is difficult to tell which part of your code is offending.

  • For debugging purposes, you can use a for loop instead of compactMap.
  • instead of passing the arguments, directly, you can assign them to constants in the for loop.

By this point, you may come to a realization, such as, instead of the property you thought you wanted to assign actually had a property on it that had the actual value you wanted to pass.

How can get the text of a div tag using only javascript (no jQuery)

Actually you dont need to call document.getElementById() function to get access to your div.

You can use this object directly by id:

text = test.textContent || test.innerText;

Find and replace - Add carriage return OR Newline

If you want to avoid the hassle of escaping the special characters in your search and replacement string when using regular expressions, do the following steps:

  1. Search for your original string, and replace it with "UniqueString42", with regular expressions off.
  2. Search for "UniqueString42" and replace it with "UniqueString42\nUniqueString1337", with regular expressions on
  3. Search for "UniqueString42" and replace it with the first line of your replacement (often your original string), with regular expressions off.
  4. Search for "UniqueString42" and replace it with the second line of your replacement, with regular expressions off.

Note that even if you want to manually pich matches for the first search and replace, you can safely use "replace all" for the three last steps.


For example, if you want to replace this:

public IFoo SomeField { get { return this.SomeField; } }

with that:

public IFoo Foo { get { return this.MyFoo; } }
public IBar Bar { get { return this.MyBar; } }

You would do the following substitutions:

  1. public IFoo SomeField { get { return this.SomeField; } } ? XOXOXOXO (regex off).
  3. XOXOXOXO ? public IFoo Foo { get { return this.MyFoo; } } (regex off).
  4. HUHUHUHU ? public IFoo Bar { get { return this.MyBar; } } (regex off).

Get ID of element that called a function

You can use 'this' in event handler:

document.getElementById("preview").onmouseover = function() {

Or pass event object to handler as follows:

document.getElementById("preview").onmouseover = function(evt) {

It's recommended to use attachEvent(for IE < 9)/addEventListener(IE9 and other browsers) to attach events. Example above is for brevity.

function myHandler(evt) {

var el = document.getElementById("preview");
if (el.addEventListener){
    el.addEventListener('click', myHandler, false); 
} else if (el.attachEvent){
    el.attachEvent('onclick', myHandler);

How do you add swap to an EC2 instance?

After applying the steps mentioned by ajtrichards you can check if your amazon free tier instance is using swap using this command

cat /proc/meminfo


ubuntu@ip-172-31-24-245:/$ cat /proc/meminfo
MemTotal:         604340 kB
MemFree:            8524 kB
Buffers:            3380 kB
Cached:           398316 kB
SwapCached:            0 kB
Active:           165476 kB
Inactive:         384556 kB
Active(anon):     141344 kB
Inactive(anon):     7248 kB
Active(file):      24132 kB
Inactive(file):   377308 kB
Unevictable:           0 kB
Mlocked:               0 kB

SwapTotal: 1048572 kB

SwapFree: 1048572 kB

Dirty:                 0 kB
Writeback:             0 kB
AnonPages:        148368 kB
Mapped:            14304 kB
Shmem:               256 kB
Slab:              26392 kB
SReclaimable:      18648 kB
SUnreclaim:         7744 kB
KernelStack:         736 kB
PageTables:         5060 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     1350740 kB
Committed_AS:     623908 kB
VmallocTotal:   34359738367 kB
VmallocUsed:        7420 kB
VmallocChunk:   34359728748 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:      637952 kB
DirectMap2M:           0 kB

How to revert initial git commit?

I will throw in what worked for me in the end. I needed to remove the initial commit on a repository as quarantined data had been misplaced, the commit had already been pushed.

Make sure you are are currently on the right branch.

git checkout master

git update-ref -d HEAD

git commit -m "Initial commit

git push -u origin master

This was able to resolve the problem.


This was on an internal repository which was not publicly accessible, if your repository was publicly accessible please assume anything you need to revert has already been pulled down by someone else.

What is the most compatible way to install python modules on a Mac?

You may already have pip3 pre-installed, so just try it!

Best practices for styling HTML emails

In addition to the answers posted here, make sure you read this article:

System has not been booted with systemd as init system (PID 1). Can't operate

This worked for me (using WSL)

sudo /etc/init.d/redis start

(for any other service, check the init.d folder for filenames)

How do you reverse a string in place in JavaScript?

function reverse(str){
var s = "";
for (var i = str.length - 1; i >= 0; i--){
    s += str[i];
return s;
reverse("your string comes here")

DOM element to corresponding vue.js component

In Vue.js 2 Inside a Vue Instance or Component:

  • Use this.$el to get the HTMLElement the instance/component was mounted to

From an HTMLElement:

  • Use .__vue__ from the HTMLElement
    • E.g. var vueInstance = document.getElementById('app').__vue__;

Having a VNode in a variable called vnode you can:

  • use vnode.elm to get the element that VNode was rendered to
  • use vnode.context to get the VueComponent instance that VNode's component was declared (this usually returns the parent component, but may surprise you when using slots.
  • use vnode.componentInstance to get the Actual VueComponent instance that VNode is about

Source, literally: vue/flow/vnode.js.

Runnable Demo:

Vue.config.productionTip = false; // disable developer version warning

Vue.component('my-component', {
  template: `<input>`,
  mounted: function() {
    console.log('[my-component] is mounted at element:', this.$el);

Vue.directive('customdirective', {
  bind: function (el, binding, vnode) {
    console.log('[DIRECTIVE] My Element is:', vnode.elm);
    console.log('[DIRECTIVE] My componentInstance is:', vnode.componentInstance);
    console.log('[DIRECTIVE] My context is:', vnode.context);
    // some properties, such as $el, may take an extra tick to be set, thus you need to...
    Vue.nextTick(() => console.log('[DIRECTIVE][AFTER TICK] My context is:', vnode.context.$el))

new Vue({
  el: '#app',
  mounted: function() {
    console.log('[ROOT] This Vue instance is mounted at element:', this.$el);
    console.log('[ROOT] From the element to the Vue instance:', document.getElementById('app').__vue__);
    console.log('[ROOT] Vue component instance of my-component:', document.querySelector('input').__vue__);
<script src="[email protected]/dist/vue.min.js"></script>

<h1>Open the browser's console</h1>
<div id="app">
  <my-component v-customdirective=""></my-component>

Insert null/empty value in sql datetime column by default

if there is no value inserted, the default value should be null,empty

In the table definition, make this datetime column allows null, be not defining NOT NULL:

DateTimeColumn DateTime,


Then , just insert NULL in this column:

INSERT INTO Table(name, datetimeColumn, ...)
VALUES('foo bar', NULL, ..);

Or, you can make use of the DEFAULT constaints:

DateTimeColumn DateTime DEFAULT NULL,

Then you can ignore it completely in the INSERT statement and it will be inserted withe the NULL value:

INSERT INTO Table(name, ...)
VALUES('foo bar', ..);

How do I configure Maven for offline development?

In preparation before working offline just run mvn dependency:go-offline

Node.js: what is ENOSPC error and how to solve?

This sounds very odd, but yes, a system reboot or killall node solves the problem for me.

Copy tables from one database to another in SQL Server

If there is existing table and we wants to copy only data, we can try this query.

insert into Destination_Existing_Tbl select col1,col2 FROM Source_Tbl

The client and server cannot communicate, because they do not possess a common algorithm - ASP.NET C# IIS TLS 1.0 / 1.1 / 1.2 - Win32Exception

This was resolved. It turns out our IT Staff was correct. Both TLS 1.1 and TLS 1.2 were installed on the server. However, the issue was that our sites are running as ASP.NET 4.0 and you have to have ASP.NET 4.5 to run TLS 1.1 or TLS 1.2. So, to resolve the issue, our IT Staff had to re-enable TLS 1.0 to allow a connection with PayTrace.

So in short, the error message, "the client and server cannot communicate, because they do not possess a common algorithm", was caused because there was no SSL Protocol available on the server to communicate with PayTrace's servers.

UPDATE: Please do not enable TLS 1.0 on your servers, this was a temporary fix and is not longer applicable since there are now better work-arounds that ensure strong security practices. Please see accepted answer for a solution. FYI, I'm going to keep this answer on the site as it provides information on what the problem was, please do not down-vote.

How can I force WebKit to redraw/repaint to propagate style changes?

I stumbled upon this today: Element.redraw() for prototype.js


  redraw: function(element){
    element = $(element);
    var n = document.createTextNode(' ');
    return element;

However, I've noticed sometimes that you must call redraw() on the problematic element directly. Sometimes redrawing the parent element won't solve the problem the child is experiencing.

Good article about the way browsers render elements: Rendering: repaint, reflow/relayout, restyle

Named colors in matplotlib

Matplotlib uses a dictionary from its module.

To print the names use:

# python2:

import matplotlib
for name, hex in matplotlib.colors.cnames.iteritems():
    print(name, hex)

# python3:

import matplotlib
for name, hex in matplotlib.colors.cnames.items():
    print(name, hex)

This is the complete dictionary:

cnames = {
'aliceblue':            '#F0F8FF',
'antiquewhite':         '#FAEBD7',
'aqua':                 '#00FFFF',
'aquamarine':           '#7FFFD4',
'azure':                '#F0FFFF',
'beige':                '#F5F5DC',
'bisque':               '#FFE4C4',
'black':                '#000000',
'blanchedalmond':       '#FFEBCD',
'blue':                 '#0000FF',
'blueviolet':           '#8A2BE2',
'brown':                '#A52A2A',
'burlywood':            '#DEB887',
'cadetblue':            '#5F9EA0',
'chartreuse':           '#7FFF00',
'chocolate':            '#D2691E',
'coral':                '#FF7F50',
'cornflowerblue':       '#6495ED',
'cornsilk':             '#FFF8DC',
'crimson':              '#DC143C',
'cyan':                 '#00FFFF',
'darkblue':             '#00008B',
'darkcyan':             '#008B8B',
'darkgoldenrod':        '#B8860B',
'darkgray':             '#A9A9A9',
'darkgreen':            '#006400',
'darkkhaki':            '#BDB76B',
'darkmagenta':          '#8B008B',
'darkolivegreen':       '#556B2F',
'darkorange':           '#FF8C00',
'darkorchid':           '#9932CC',
'darkred':              '#8B0000',
'darksalmon':           '#E9967A',
'darkseagreen':         '#8FBC8F',
'darkslateblue':        '#483D8B',
'darkslategray':        '#2F4F4F',
'darkturquoise':        '#00CED1',
'darkviolet':           '#9400D3',
'deeppink':             '#FF1493',
'deepskyblue':          '#00BFFF',
'dimgray':              '#696969',
'dodgerblue':           '#1E90FF',
'firebrick':            '#B22222',
'floralwhite':          '#FFFAF0',
'forestgreen':          '#228B22',
'fuchsia':              '#FF00FF',
'gainsboro':            '#DCDCDC',
'ghostwhite':           '#F8F8FF',
'gold':                 '#FFD700',
'goldenrod':            '#DAA520',
'gray':                 '#808080',
'green':                '#008000',
'greenyellow':          '#ADFF2F',
'honeydew':             '#F0FFF0',
'hotpink':              '#FF69B4',
'indianred':            '#CD5C5C',
'indigo':               '#4B0082',
'ivory':                '#FFFFF0',
'khaki':                '#F0E68C',
'lavender':             '#E6E6FA',
'lavenderblush':        '#FFF0F5',
'lawngreen':            '#7CFC00',
'lemonchiffon':         '#FFFACD',
'lightblue':            '#ADD8E6',
'lightcoral':           '#F08080',
'lightcyan':            '#E0FFFF',
'lightgoldenrodyellow': '#FAFAD2',
'lightgreen':           '#90EE90',
'lightgray':            '#D3D3D3',
'lightpink':            '#FFB6C1',
'lightsalmon':          '#FFA07A',
'lightseagreen':        '#20B2AA',
'lightskyblue':         '#87CEFA',
'lightslategray':       '#778899',
'lightsteelblue':       '#B0C4DE',
'lightyellow':          '#FFFFE0',
'lime':                 '#00FF00',
'limegreen':            '#32CD32',
'linen':                '#FAF0E6',
'magenta':              '#FF00FF',
'maroon':               '#800000',
'mediumaquamarine':     '#66CDAA',
'mediumblue':           '#0000CD',
'mediumorchid':         '#BA55D3',
'mediumpurple':         '#9370DB',
'mediumseagreen':       '#3CB371',
'mediumslateblue':      '#7B68EE',
'mediumspringgreen':    '#00FA9A',
'mediumturquoise':      '#48D1CC',
'mediumvioletred':      '#C71585',
'midnightblue':         '#191970',
'mintcream':            '#F5FFFA',
'mistyrose':            '#FFE4E1',
'moccasin':             '#FFE4B5',
'navajowhite':          '#FFDEAD',
'navy':                 '#000080',
'oldlace':              '#FDF5E6',
'olive':                '#808000',
'olivedrab':            '#6B8E23',
'orange':               '#FFA500',
'orangered':            '#FF4500',
'orchid':               '#DA70D6',
'palegoldenrod':        '#EEE8AA',
'palegreen':            '#98FB98',
'paleturquoise':        '#AFEEEE',
'palevioletred':        '#DB7093',
'papayawhip':           '#FFEFD5',
'peachpuff':            '#FFDAB9',
'peru':                 '#CD853F',
'pink':                 '#FFC0CB',
'plum':                 '#DDA0DD',
'powderblue':           '#B0E0E6',
'purple':               '#800080',
'red':                  '#FF0000',
'rosybrown':            '#BC8F8F',
'royalblue':            '#4169E1',
'saddlebrown':          '#8B4513',
'salmon':               '#FA8072',
'sandybrown':           '#FAA460',
'seagreen':             '#2E8B57',
'seashell':             '#FFF5EE',
'sienna':               '#A0522D',
'silver':               '#C0C0C0',
'skyblue':              '#87CEEB',
'slateblue':            '#6A5ACD',
'slategray':            '#708090',
'snow':                 '#FFFAFA',
'springgreen':          '#00FF7F',
'steelblue':            '#4682B4',
'tan':                  '#D2B48C',
'teal':                 '#008080',
'thistle':              '#D8BFD8',
'tomato':               '#FF6347',
'turquoise':            '#40E0D0',
'violet':               '#EE82EE',
'wheat':                '#F5DEB3',
'white':                '#FFFFFF',
'whitesmoke':           '#F5F5F5',
'yellow':               '#FFFF00',
'yellowgreen':          '#9ACD32'}

You could plot them like this:

import matplotlib.pyplot as plt
import matplotlib.patches as patches
import matplotlib.colors as colors
import math

fig = plt.figure()
ax = fig.add_subplot(111)

ratio = 1.0 / 3.0
count = math.ceil(math.sqrt(len(colors.cnames)))
x_count = count * ratio
y_count = count / ratio
x = 0
y = 0
w = 1 / x_count
h = 1 / y_count

for c in colors.cnames:
    pos = (x / x_count, y / y_count)
    ax.add_patch(patches.Rectangle(pos, w, h, color=c))
    ax.annotate(c, xy=pos)
    if y >= y_count-1:
        x += 1
        y = 0
        y += 1

Eclipse reports rendering library more recent than ADT plug-in

Change android version while rendering layout.

enter image description here

Change in API version 18 to 17 work for me.

Edit: Solution worked for Android Studio too.

How do we count rows using older versions of Hibernate (~2009)?

Here is what official hibernate docs tell us about this:

You can count the number of query results without returning them:

( (Integer) session.createQuery("select count(*) from ....").iterate().next() ).intValue()

However, it doesn't always return Integer instance, so it is better to use java.lang.Number for safety.

How to call a method in another class in Java?

Instead of using this in your current class setClassRoomName("aClassName"); you have to use classroom.setClassRoomName("aClassName");

You have to add the class' and at a point like


I know it's a really late answer but if someone starts learning Java and randomly sees this post he knows what to do.

how to know status of currently running jobs

EXECUTE master.dbo.xp_sqlagent_enum_jobs 1,''

Notice the column Running, obviously 1 means that it is currently running, and [Current Step]. This returns job_id to you, so you'll need to look these up, e.g.:

SELECT top 100 *
 FROM   msdb..sysjobs
 WHERE  job_id IN (0x9DAD1B38EB345D449EAFA5C5BFDC0E45, 0xC00A0A67D109B14897DD3DFD25A50B80, 0xC92C66C66E391345AE7E731BFA68C668)

What is the difference between ManualResetEvent and AutoResetEvent in .NET?


is similar to


as an atomic operation

Relay access denied on sending mail, Other domain outside of network

I'm using THUNDERBIRD as MUA and I have same issues. I solved adding the IP address of my home PC on mynetworks parameter on

mynetworks = [::ffff:]/104 [::1]/128 MyIpAddress

P.S. I don't have a static ip for my home PC so when my ISP change it I ave to adjust every time.

What is the use of WPFFontCache Service in WPF? WPFFontCache_v0400.exe taking 100 % CPU all the time this exe is running, why?

Use This its is very useful for your solution:

  1. Start > Control Panel > Administrative Tools > Services
  2. Scroll down to 'Windows Presentation Foundation Font Cache' and then right click and select properties
  3. In the window then select 'disabled' in the startup type combo

How to fetch FetchType.LAZY associations with JPA and Hibernate in a Spring Controller

You will have to make an explicit call on the lazy collection in order to initialize it (common practice is to call .size() for this purpose). In Hibernate there is a dedicated method for this (Hibernate.initialize()), but JPA has no equivalent of that. Of course you will have to make sure that the invocation is done, when the session is still available, so annotate your controller method with @Transactional. An alternative is to create an intermediate Service layer between the Controller and the Repository that could expose methods which initialize lazy collections.


Please note that the above solution is easy, but results in two distinct queries to the database (one for the user, another one for its roles). If you want to achieve better performace add the following method to your Spring Data JPA repository interface:

public interface PersonRepository extends JpaRepository<Person, Long> {

    @Query("SELECT p FROM Person p JOIN FETCH p.roles WHERE = (:id)")
    public Person findByIdAndFetchRolesEagerly(@Param("id") Long id);


This method will use JPQL's fetch join clause to eagerly load the roles association in a single round-trip to the database, and will therefore mitigate the performance penalty incurred by the two distinct queries in the above solution.

Session 'app': Error Installing APK

If you are using android emulator, try changing a device.

How do I display image in Alert/confirm box in Javascript?

I created a function that might help. All it does is imitate the alert but put an image instead of text.

function alertImage(imgsrc) {
    'position': 'absolute',
    'top': '0',
    'left': '50%',
    '-webkit-transform': 'translate(-50%, 0)'
    opacity: 0
}, 0)
    opacity: 1,
    top: "10px"
}, 250)
$('.d').append('An embedded page on this page says')
$('.d').append('<br><img src="' + imgsrc + '">')
  '-webkit-transform': 'translate(-100%, -100%)',
<script type="text/javascript" src=""></script>
<div class="d"><button onclick="$('.d').html('')" class="b">OK</button></div>
font-size: 17px;
  font-family: sans-serif;
  display: none;

How to increment a datetime by one day?

All of the current answers are wrong in some cases as they do not consider that timezones change their offset relative to UTC. So in some cases adding 24h is different from adding a calendar day.

Proposed solution

The following solution works for Samoa and keeps the local time constant.

def add_day(today):
    Add a day to the current day.

    This takes care of historic offset changes and DST.

    today : timezone-aware datetime object

    tomorrow : timezone-aware datetime object
    today_utc = today.astimezone(datetime.timezone.utc)
    tz = today.tzinfo
    tomorrow_utc = today_utc + datetime.timedelta(days=1)
    tomorrow_utc_tz = tomorrow_utc.astimezone(tz)
    tomorrow_utc_tz = tomorrow_utc_tz.replace(hour=today.hour,
    return tomorrow_utc_tz

Tested Code

# core modules
import datetime

# 3rd party modules
import pytz

# add_day methods
def add_day(today):
    Add a day to the current day.

    This takes care of historic offset changes and DST.

    today : timezone-aware datetime object

    tomorrow : timezone-aware datetime object
    today_utc = today.astimezone(datetime.timezone.utc)
    tz = today.tzinfo
    tomorrow_utc = today_utc + datetime.timedelta(days=1)
    tomorrow_utc_tz = tomorrow_utc.astimezone(tz)
    tomorrow_utc_tz = tomorrow_utc_tz.replace(hour=today.hour,
    return tomorrow_utc_tz

def add_day_datetime_timedelta_conversion(today):
    # Correct for Samoa, but dst shift
    today_utc = today.astimezone(datetime.timezone.utc)
    tz = today.tzinfo
    tomorrow_utc = today_utc + datetime.timedelta(days=1)
    tomorrow_utc_tz = tomorrow_utc.astimezone(tz)
    return tomorrow_utc_tz

def add_day_dateutil_relativedelta(today):
    # WRONG!
    from dateutil.relativedelta import relativedelta
    return today + relativedelta(days=1)

def add_day_datetime_timedelta(today):
    # WRONG!
    return today + datetime.timedelta(days=1)

# Test cases
def test_samoa(add_day):
    Test if add_day properly increases the calendar day for Samoa.

    Due to economic considerations, Samoa went from 2011-12-30 10:00-11:00
    to 2011-12-30 10:00+13:00. Hence the country skipped 2011-12-30 in its
    local time.


    A common wrong result here is 2011-12-30T23:59:00-10:00. This date never
    happened in Samoa.
    tz = pytz.timezone('Pacific/Apia')
    today_utc = datetime.datetime(2011, 12, 30, 9, 59,
    today_tz = today_utc.astimezone(tz)  # 2011-12-29T23:59:00-10:00
    tomorrow = add_day(today_tz)
    return tomorrow.isoformat() == '2011-12-31T23:59:00+14:00'

def test_dst(add_day):
    """Test if add_day properly increases the calendar day if DST happens."""
    tz = pytz.timezone('Europe/Berlin')
    today_utc = datetime.datetime(2018, 3, 25, 0, 59,
    today_tz = today_utc.astimezone(tz)  # 2018-03-25T01:59:00+01:00
    tomorrow = add_day(today_tz)
    return tomorrow.isoformat() == '2018-03-26T01:59:00+02:00'

to_test = [(add_day_dateutil_relativedelta, 'relativedelta'),
           (add_day_datetime_timedelta, 'timedelta'),
           (add_day_datetime_timedelta_conversion, 'timedelta+conversion'),
           (add_day, 'timedelta+conversion+dst')]
print('{:<25}: {:>5} {:>5}'.format('Method', 'Samoa', 'DST'))
for method, name in to_test:
    print('{:<25}: {:>5} {:>5}'

Test results

Method                   : Samoa   DST
relativedelta            :     0     0
timedelta                :     0     0
timedelta+conversion     :     1     0
timedelta+conversion+dst :     1     1

How to round the corners of a button

For Swift:

button.layer.cornerRadius = 10.0

How to add a form load event (currently not working)

You got half of the answer! Now that you created the event handler, you need to hook it to the form so that it actually gets called when the form is loading. You can achieve that by doing the following:

 public class ProgramViwer : Form{
  public ProgramViwer()
       Load += new EventHandler(ProgramViwer_Load);
  private void ProgramViwer_Load(object sender, System.EventArgs e)

What is the difference between concurrency and parallelism?

From the book Linux System Programming by Robert Love:

Concurrency, Parallelism, and Races

Threads create two related but distinct phenomena: concurrency and parallelism. Both are bittersweet, touching on the costs of threading as well as its benefits. Concurrency is the ability of two or more threads to execute in overlapping time periods. Parallelism is the ability to execute two or more threads simultaneously. Concurrency can occur without parallelism: for example, multitasking on a single processor system. Parallelism (sometimes emphasized as true parallelism) is a specific form of concurrency requiring multiple processors (or a single processor capable of multiple engines of execution, such as a GPU). With concurrency, multiple threads make forward progress, but not necessarily simultaneously. With parallelism, threads literally execute in parallel, allowing multithreaded programs to utilize multiple processors.

Concurrency is a programming pattern, a way of approaching problems. Parallelism is a hardware feature, achievable through concurrency. Both are useful.

This explanation is consistent with the accepted answer. Actually the concepts are far simpler than we think. Don't think them as magic. Concurrency is about a period of time, while Parallelism is about exactly at the same time, simultaneously.

Does this app use the Advertising Identifier (IDFA)? - AdMob 6.8.0

If you have Google analytics or Facebook api in you app, you need to check all of them to make sure it works!

Edit: This is an old answer - see comments or other answers for an exact answer.

SOAP request in PHP with CURL

Tested and working!

  • with https, user & password

     //Data, connection, auth
     $dataFromTheForm = $_POST['fieldName']; // request data from the form
     $soapUrl = ""; // asmx URL of WSDL
     $soapUser = "username";  //  username
     $soapPassword = "password"; // password
     // xml post structure
     $xml_post_string = '<?xml version="1.0" encoding="utf-8"?>
                         <soap:Envelope xmlns:xsi="" xmlns:xsd="" xmlns:soap="">
                             <GetItemPrice xmlns=""> // xmlns value to be set to your WSDL URL
                             </GetItemPrice >
                         </soap:Envelope>';   // data from the form, e.g. some ID number
        $headers = array(
                     "Content-type: text/xml;charset=\"utf-8\"",
                     "Accept: text/xml",
                     "Cache-Control: no-cache",
                     "Pragma: no-cache",
                     "Content-length: ".strlen($xml_post_string),
                 ); //SOAPAction: your op URL
         $url = $soapUrl;
         // PHP cURL  for https connection with auth
         $ch = curl_init();
         curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 1);
         curl_setopt($ch, CURLOPT_URL, $url);
         curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
         curl_setopt($ch, CURLOPT_USERPWD, $soapUser.":".$soapPassword); // username and password - declared at the top of the doc
         curl_setopt($ch, CURLOPT_HTTPAUTH, CURLAUTH_ANY);
         curl_setopt($ch, CURLOPT_TIMEOUT, 10);
         curl_setopt($ch, CURLOPT_POST, true);
         curl_setopt($ch, CURLOPT_POSTFIELDS, $xml_post_string); // the SOAP request
         curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
         // converting
         $response = curl_exec($ch); 
         // converting
         $response1 = str_replace("<soap:Body>","",$response);
         $response2 = str_replace("</soap:Body>","",$response1);
         // convertingc to XML
         $parser = simplexml_load_string($response2);
         // user $parser to get your data out of XML response and to display it. 

Why is using a wild card with a Java import statement bad?

For the record: When you add an import, you are also indicating your dependencies.

You could see quickly what are the dependencies of files (excluding classes of the same namespace).

What is the function __construct used for?

__construct() is the method name for the constructor. The constructor is called on an object after it has been created, and is a good place to put initialisation code, etc.

class Person {

    public function __construct() {
        // Code called for each new Person we create


$person = new Person();

A constructor can accept parameters in the normal manner, which are passed when the object is created, e.g.

class Person {

    public $name = '';

    public function __construct( $name ) {
        $this->name = $name;


$person = new Person( "Joe" );
echo $person->name;

Unlike some other languages (e.g. Java), PHP doesn't support overloading the constructor (that is, having multiple constructors which accept different parameters). You can achieve this effect using static methods.

Note: I retrieved this from the log of the (at time of this writing) accepted answer.

Precision String Format Specifier In Swift

What about extensions on Double and CGFloat types:

extension Double {

   func formatted(_ decimalPlaces: Int?) -> String {
      let theDecimalPlaces : Int
      if decimalPlaces != nil {
         theDecimalPlaces = decimalPlaces!
      else {
         theDecimalPlaces = 2
      let theNumberFormatter = NumberFormatter()
      theNumberFormatter.formatterBehavior = .behavior10_4
      theNumberFormatter.minimumIntegerDigits = 1
      theNumberFormatter.minimumFractionDigits = 1
      theNumberFormatter.maximumFractionDigits = theDecimalPlaces
      theNumberFormatter.usesGroupingSeparator = true
      theNumberFormatter.groupingSeparator = " "
      theNumberFormatter.groupingSize = 3

      if let theResult = theNumberFormatter.string(from: NSNumber(value:self)) {
         return theResult
      else {
         return "\(self)"


let aNumber: Double = 112465848348508.458758344
Swift.print("The number: \(aNumber.formatted(2))")

prints: 112 465 848 348 508.46

How to upload, display and save images using node.js and express

First of all, you should make an HTML form containing a file input element. You also need to set the form's enctype attribute to multipart/form-data:

<form method="post" enctype="multipart/form-data" action="/upload">
    <input type="file" name="file">
    <input type="submit" value="Submit">

Assuming the form is defined in index.html stored in a directory named public relative to where your script is located, you can serve it this way:

const http = require("http");
const path = require("path");
const fs = require("fs");

const express = require("express");

const app = express();
const httpServer = http.createServer(app);

const PORT = process.env.PORT || 3000;

httpServer.listen(PORT, () => {
  console.log(`Server is listening on port ${PORT}`);

// put the HTML file containing your form in a directory named "public" (relative to where this script is located)
app.get("/", express.static(path.join(__dirname, "./public")));

Once that's done, users will be able to upload files to your server via that form. But to reassemble the uploaded file in your application, you'll need to parse the request body (as multipart form data).

In Express 3.x you could use express.bodyParser middleware to handle multipart forms but as of Express 4.x, there's no body parser bundled with the framework. Luckily, you can choose from one of the many available multipart/form-data parsers out there. Here, I'll be using multer:

You need to define a route to handle form posts:

const multer = require("multer");

const handleError = (err, res) => {
    .end("Oops! Something went wrong!");

const upload = multer({
  dest: "/path/to/temporary/directory/to/store/uploaded/files"
  // you might also want to set some limits:
  upload.single("file" /* name attribute of <file> element in your form */),
  (req, res) => {
    const tempPath = req.file.path;
    const targetPath = path.join(__dirname, "./uploads/image.png");

    if (path.extname(req.file.originalname).toLowerCase() === ".png") {
      fs.rename(tempPath, targetPath, err => {
        if (err) return handleError(err, res);

          .end("File uploaded!");
    } else {
      fs.unlink(tempPath, err => {
        if (err) return handleError(err, res);

          .end("Only .png files are allowed!");

In the example above, .png files posted to /upload will be saved to uploaded directory relative to where the script is located.

In order to show the uploaded image, assuming you already have an HTML page containing an img element:

<img src="/image.png" />

you can define another route in your express app and use res.sendFile to serve the stored image:

app.get("/image.png", (req, res) => {
  res.sendFile(path.join(__dirname, "./uploads/image.png"));

How do I check if a list is empty?

The pythonic way to do it is from the PEP 8 style guide (where Yes means “recommended” and No means “not recommended”):

For sequences, (strings, lists, tuples), use the fact that empty sequences are false.

Yes: if not seq:
     if seq:

No:  if len(seq):
     if not len(seq):

How can I parse a String to BigDecimal?

Try this

// Create a DecimalFormat that fits your requirements
DecimalFormatSymbols symbols = new DecimalFormatSymbols();
String pattern = "#,##0.0#";
DecimalFormat decimalFormat = new DecimalFormat(pattern, symbols);

// parse the string
BigDecimal bigDecimal = (BigDecimal) decimalFormat.parse("10,692,467,440,017.120");

If you are building an application with I18N support you should use DecimalFormatSymbols(Locale)

Also keep in mind that decimalFormat.parse can throw a ParseException so you need to handle it (with try/catch) or throw it and let another part of your program handle it

What is the difference between Amazon SNS and Amazon SQS?

SNS is a distributed publish-subscribe system. Messages are pushed to subscribers as and when they are sent by publishers to SNS.

SQS is distributed queuing system. Messages are not pushed to receivers. Receivers have to poll or pull messages from SQS. Messages can't be received by multiple receivers at the same time. Any one receiver can receive a message, process and delete it. Other receivers do not receive the same message later. Polling inherently introduces some latency in message delivery in SQS unlike SNS where messages are immediately pushed to subscribers. SNS supports several end points such as email, SMS, HTTP end point and SQS. If you want unknown number and type of subscribers to receive messages, you need SNS.

You don't have to couple SNS and SQS always. You can have SNS send messages to email, SMS or HTTP end point apart from SQS. There are advantages to coupling SNS with SQS. You may not want an external service to make connections to your hosts (a firewall may block all incoming connections to your host from outside).

Your end point may just die because of heavy volume of messages. Email and SMS maybe not your choice of processing messages quickly. By coupling SNS with SQS, you can receive messages at your pace. It allows clients to be offline, tolerant to network and host failures. You also achieve guaranteed delivery. If you configure SNS to send messages to an HTTP end point or email or SMS, several failures to send message may result in messages being dropped.

SQS is mainly used to decouple applications or integrate applications. Messages can be stored in SQS for a short duration of time (maximum 14 days). SNS distributes several copies of messages to several subscribers. For example, let’s say you want to replicate data generated by an application to several storage systems. You could use SNS and send this data to multiple subscribers, each replicating the messages it receives to different storage systems (S3, hard disk on your host, database, etc.).

Android Transparent TextView?

See the Android Color resource documentation for reference.

Basically you have the option to set the transparency (opacity) and the color either directly in the layout or using resources references.

The hex value that you set it to is composed of 3 to 4 parts:

  • Alpha (opacity), i'll refer to that as aa

  • Red, i'll refer to it as rr

  • Green, i'll refer to it as gg

  • Blue, i'll refer to it as bb

Without an alpha (transparency) value:


or as resource:

<color name="my_color">#rrggbb</color>

With an alpha (transparency) value:


or as resource:

<color name="my_color">#aarrggbb</color>

The alpha value for full transparency is 00 and the alpha value for no transparency is FF.

See full range of hex values below:

100% — FF
 95% — F2
 90% — E6
 85% — D9
 80% — CC
 75% — BF
 70% — B3
 65% — A6
 60% — 99
 55% — 8C
 50% — 80
 45% — 73
 40% — 66
 35% — 59
 30% — 4D
 25% — 40
 20% — 33
 15% — 26
 10% — 1A
  5% — 0D
  0% — 00

You can experiment with values in between those.

How to get different colored lines for different plots in a single figure?

Matplotlib does this by default.


import matplotlib.pyplot as plt
import numpy as np

x = np.arange(10)

plt.plot(x, x)
plt.plot(x, 2 * x)
plt.plot(x, 3 * x)
plt.plot(x, 4 * x)

Basic plot demonstrating color cycling

And, as you may already know, you can easily add a legend:

import matplotlib.pyplot as plt
import numpy as np

x = np.arange(10)

plt.plot(x, x)
plt.plot(x, 2 * x)
plt.plot(x, 3 * x)
plt.plot(x, 4 * x)

plt.legend(['y = x', 'y = 2x', 'y = 3x', 'y = 4x'], loc='upper left')

Basic plot with legend

If you want to control the colors that will be cycled through:

import matplotlib.pyplot as plt
import numpy as np

x = np.arange(10)

plt.gca().set_color_cycle(['red', 'green', 'blue', 'yellow'])

plt.plot(x, x)
plt.plot(x, 2 * x)
plt.plot(x, 3 * x)
plt.plot(x, 4 * x)

plt.legend(['y = x', 'y = 2x', 'y = 3x', 'y = 4x'], loc='upper left')

Plot showing control over default color cycling

If you're unfamiliar with matplotlib, the tutorial is a good place to start.


First off, if you have a lot (>5) of things you want to plot on one figure, either:

  1. Put them on different plots (consider using a few subplots on one figure), or
  2. Use something other than color (i.e. marker styles or line thickness) to distinguish between them.

Otherwise, you're going to wind up with a very messy plot! Be nice to who ever is going to read whatever you're doing and don't try to cram 15 different things onto one figure!!

Beyond that, many people are colorblind to varying degrees, and distinguishing between numerous subtly different colors is difficult for more people than you may realize.

That having been said, if you really want to put 20 lines on one axis with 20 relatively distinct colors, here's one way to do it:

import matplotlib.pyplot as plt
import numpy as np

num_plots = 20

# Have a look at the colormaps here and decide which one you'd like:
colormap =
plt.gca().set_prop_cycle(plt.cycler('color',, 1, num_plots))))

# Plot several different functions...
x = np.arange(10)
labels = []
for i in range(1, num_plots + 1):
    plt.plot(x, i * x + 5 * i)
    labels.append(r'$y = %ix + %i$' % (i, 5*i))

# I'm basically just demonstrating several different legend options here...
plt.legend(labels, ncol=4, loc='upper center', 
           bbox_to_anchor=[0.5, 1.1], 
           columnspacing=1.0, labelspacing=0.0,
           handletextpad=0.0, handlelength=1.5,
           fancybox=True, shadow=True)

Unique colors for 20 lines based on a given colormap

Div Background Image Z-Index Issue

Set your header and footer position to "absolute" and that should do the trick. Hope it helps and good luck with your project!

Removing NA observations with dplyr::filter()

From @Ben Bolker:

[T]his has nothing specifically to do with dplyr::filter()

From @Marat Talipov:

[A]ny comparison with NA, including NA==NA, will return NA

From a related answer by @farnsy:

The == operator does not treat NA's as you would expect it to.

Think of NA as meaning "I don't know what's there". The correct answer to 3 > NA is obviously NA because we don't know if the missing value is larger than 3 or not. Well, it's the same for NA == NA. They are both missing values but the true values could be quite different, so the correct answer is "I don't know."

R doesn't know what you are doing in your analysis, so instead of potentially introducing bugs that would later end up being published an embarrassing you, it doesn't allow comparison operators to think NA is a value.

How can I remove a key from a Python dictionary?

If you need to remove a lot of keys from a dictionary in one line of code, I think using map() is quite succinct and Pythonic readable:

myDict = {'a':1,'b':2,'c':3,'d':4}
map(myDict.pop, ['a','c']) # The list of keys to remove
>>> myDict
{'b': 2, 'd': 4}

And if you need to catch errors where you pop a value that isn't in the dictionary, use lambda inside map() like this:

map(lambda x: myDict.pop(x,None), ['a', 'c', 'e'])
[1, 3, None] # pop returns
>>> myDict
{'b': 2, 'd': 4}

or in python3, you must use a list comprehension instead:

[myDict.pop(x, None) for x in ['a', 'c', 'e']]

It works. And 'e' did not cause an error, even though myDict did not have an 'e' key.

How to store a datetime in MySQL with timezone info

All the symptoms you describe suggest that you never tell MySQL what time zone to use so it defaults to system's zone. Think about it: if all it has is '2011-03-13 02:49:10', how can it guess that it's a local Tanzanian date?

As far as I know, MySQL doesn't provide any syntax to specify time zone information in dates. You have to change it a per-connection basis; something like:

SET time_zone = 'EAT';

If this doesn't work (to use named zones you need that the server has been configured to do so and it's often not the case) you can use UTC offsets because Tanzania does not observe daylight saving time at the time of writing but of course it isn't the best option:

SET time_zone = '+03:00';

Convert a string to datetime in PowerShell

Chris Dents' answer has already covered the OPs' question but seeing as this was the top search on google for PowerShell format string as date I thought I'd give a different string example.

If like me, you get the time string like this 20190720170000.000000+000

An important thing to note is you need to use ToUniversalTime() when using [System.Management.ManagementDateTimeConverter] otherwise you get offset times against your input.

PS Code

Write-Host "This example is for the 24hr clock with HH"
Write-Host "ToUniversalTime() must be used when using [System.Management.ManagementDateTimeConverter]"
$my_date_24hr_time   = "20190720170000.000000+000"
$date_format         = "yyyy-MM-dd HH:mm"
Write-Host "-----------------------------"
Write-Host "This example is for the am pm clock with hh"
Write-Host "Again, ToUniversalTime() must be used when using [System.Management.ManagementDateTimeConverter]"
$my_date_ampm_time   = "20190720110000.000000+000"


This example is for the 24hr clock with HH
ToUniversalTime() must be used when using [System.Management.ManagementDateTimeConverter]

20 July 2019 17:00:00
2019-07-20 17:00
2019-07-20 17:00


This example is for the am pm clock with hh
Again, ToUniversalTime() must be used when using [System.Management.ManagementDateTimeConverter]

20 July 2019 11:00:00
2019-07-20 11:00
2019-07-20 11:00

MS doc on [Management.ManagementDateTimeConverter]:

Python virtualenv questions

After creating virtual environment copy the activate.bat file from Script folder of python and paste to it your environment and open cmd from your virtual environment and run activate.bat file.enter image description here

What is the optimal way to compare dates in Microsoft SQL server?

Get items when the date is between fromdate and toDate.

where convert(date, fromdate, 103 ) <= '2016-07-26' and convert(date, toDate, 103) >= '2016-07-26'

Pass table as parameter into sql server UDF


Step 1:

CREATE TABLE [DBO].T_EMPLOYEES_DETAILS ( Id int, Name nvarchar(50), Gender nvarchar(10), Salary int )

Step 2:

CREATE TYPE EmpInsertType AS TABLE ( Id int, Name nvarchar(50), Gender nvarchar(10), Salary int )

Step 3:

/* Must add READONLY keyword at end of the variable */


Step 4:

DECLARE @EmployeeInsertType EmpInsertType

INSERT INTO @EmployeeInsertType VALUES(1,'John','Male',50000) INSERT INTO @EmployeeInsertType VALUES(2,'Praveen','Male',60000) INSERT INTO @EmployeeInsertType VALUES(3,'Chitra','Female',45000) INSERT INTO @EmployeeInsertType VALUES(4,'Mathy','Female',6600) INSERT INTO @EmployeeInsertType VALUES(5,'Sam','Male',50000)

EXEC PRC_EmpInsertType @EmployeeInsertType




1 John Male 50000

2 Praveen Male 60000

3 Chitra Female 45000

4 Mathy Female 6600

5 Sam Male 50000

Break promise chain and call a function based on the step in the chain where it is broken (rejected)

Try ro use this like libs:

.then(pb((data) => {
    if (!data.someCheck()) {

        // All other '.then' calls will be skiped
        return pb.BREAK;
.then(pb(() => {
.then(pb(() => {
.catch((error) => {

List Highest Correlation Pairs from a Large Correlation Matrix in Pandas?

Combining some features of @HYRY and @arun's answers, you can print the top correlations for dataframe df in a single line using:


Note: the one downside is if you have 1.0 correlations that are not one variable to itself, the drop_duplicates() addition would remove them

How to catch segmentation fault in Linux?

Here's an example of how to do it in C.

#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void segfault_sigaction(int signal, siginfo_t *si, void *arg)
    printf("Caught segfault at address %p\n", si->si_addr);

int main(void)
    int *foo = NULL;
    struct sigaction sa;

    memset(&sa, 0, sizeof(struct sigaction));
    sa.sa_sigaction = segfault_sigaction;
    sa.sa_flags   = SA_SIGINFO;

    sigaction(SIGSEGV, &sa, NULL);

    /* Cause a seg fault */
    *foo = 1;

    return 0;

Check if element is visible in DOM

If you're interested in visible by the user:

function isVisible(elem) {
    if (!(elem instanceof Element)) throw Error('DomUtil: elem is not an element.');
    const style = getComputedStyle(elem);
    if (style.display === 'none') return false;
    if (style.visibility !== 'visible') return false;
    if (style.opacity < 0.1) return false;
    if (elem.offsetWidth + elem.offsetHeight + elem.getBoundingClientRect().height +
        elem.getBoundingClientRect().width === 0) {
        return false;
    const elemCenter   = {
        x: elem.getBoundingClientRect().left + elem.offsetWidth / 2,
        y: elem.getBoundingClientRect().top + elem.offsetHeight / 2
    if (elemCenter.x < 0) return false;
    if (elemCenter.x > (document.documentElement.clientWidth || window.innerWidth)) return false;
    if (elemCenter.y < 0) return false;
    if (elemCenter.y > (document.documentElement.clientHeight || window.innerHeight)) return false;
    let pointContainer = document.elementFromPoint(elemCenter.x, elemCenter.y);
    do {
        if (pointContainer === elem) return true;
    } while (pointContainer = pointContainer.parentNode);
    return false;

Tested on (using mocha terminology):

describe.only('visibility', function () {
    let div, visible, notVisible, inViewport, leftOfViewport, rightOfViewport, aboveViewport,
        belowViewport, notDisplayed, zeroOpacity, zIndex1, zIndex2;
    before(() => {
        div = document.createElement('div');
        div.appendChild(visible = document.createElement('div'));       = 'border: 1px solid black; margin: 5px; display: inline-block;';
        visible.textContent = 'visible';
        div.appendChild(inViewport = visible.cloneNode(false));
        inViewport.textContent = 'inViewport';
        div.appendChild(notDisplayed = visible.cloneNode(false)); = 'none';
        notDisplayed.textContent   = 'notDisplayed';
        div.appendChild(notVisible = visible.cloneNode(false)); = 'hidden';
        notVisible.textContent      = 'notVisible';
        div.appendChild(leftOfViewport = visible.cloneNode(false)); = 'absolute'; = '100000px';
        leftOfViewport.textContent = 'leftOfViewport';
        div.appendChild(rightOfViewport = leftOfViewport.cloneNode(false));       = '0';       = '100000px';
        rightOfViewport.textContent = 'rightOfViewport';
        div.appendChild(aboveViewport = leftOfViewport.cloneNode(false));       = '0';       = '100000px';
        aboveViewport.textContent = 'aboveViewport';
        div.appendChild(belowViewport = leftOfViewport.cloneNode(false));       = '0';       = '100000px';
        belowViewport.textContent = 'belowViewport';
        div.appendChild(zeroOpacity = visible.cloneNode(false));
        zeroOpacity.textContent   = 'zeroOpacity'; = '0';
        div.appendChild(zIndex1 = visible.cloneNode(false));
        zIndex1.textContent = 'zIndex1'; = 'absolute'; = = = = '100px'; = '1';
        div.appendChild(zIndex2 = zIndex1.cloneNode(false));
        zIndex2.textContent = 'zIndex2'; = = '90px'; = = '120px'; = 'red'; = '2';
    after(() => {
    it('isVisible = true', () => {
    it('isVisible = false', () => {

Injecting @Autowired private field during testing

Sometimes you can refactor your @Component to use constructor or setter based injection to setup your testcase (you can and still rely on @Autowired). Now, you can create your test entirely without a mocking framework by implementing test stubs instead (e.g. Martin Fowler's MailServiceStub):

public class MyLauncher {

    private MyService myService;

    MyLauncher(MyService myService) {
        this.myService = myService;

    // other methods

public class MyServiceStub implements MyService {
    // ...

public class MyLauncherTest
    private MyLauncher myLauncher;
    private MyServiceStub myServiceStub;

    public void setUp() {
        myServiceStub = new MyServiceStub();
        myLauncher = new MyLauncher(myServiceStub);

    public void someTest() {


This technique especially useful if the test and the class under test is located in the same package because then you can use the default, package-private access modifier to prevent other classes from accessing it. Note that you can still have your production code in src/main/java but your tests in src/main/test directories.

If you like Mockito then you will appreciate the MockitoJUnitRunner. It allows you to do "magic" things like @Manuel showed you:

public class MyLauncherTest
    private MyLauncher myLauncher; // no need to call the constructor

    private MyService myService;

    public void someTest() {


Alternatively, you can use the default JUnit runner and call the MockitoAnnotations.initMocks() in a setUp() method to let Mockito initialize the annotated values. You can find more information in the javadoc of @InjectMocks and in a blog post that I have written.

preg_match in JavaScript?

Some Googling brought me to this :

function preg_match (regex, str) {
  return (new RegExp(regex).test(str))
console.log(preg_match("^[a-zA-Z0-9._-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,6}$","[email protected]"))

See for more info.

In Java, how do I get the difference in seconds between 2 dates?

You should do

org.joda.time.Seconds.secondBetween(date1, date2)

Web scraping with Python

Here is a simple web crawler, i used BeautifulSoup and we will search for all the links(anchors) who's class name is _3NFO0d. I used, it is an online retailing store.

import requests
from bs4 import BeautifulSoup
def crawl_flipkart():
    url = ''
    source_code = requests.get(url)
    plain_text = source_code.text
    soup = BeautifulSoup(plain_text, "lxml")
    for link in soup.findAll('a', {'class': '_3NFO0d'}):
        href = link.get('href')


Git Bash won't run my python files?

Adapting the PATH should work. Just tried on my Git bash:

$ python --version
sh.exe": python: command not found

$ PATH=$PATH:/c/Python27/

$ python --version
Python 2.7.6

In particular, only provide the directory; don't specify the .exe on the PATH ; and use slashes.

MySQL SELECT last few days?

Use for a date three days ago:


Check the DATE_ADD documentation.

Or you can use:


How to create an Array, ArrayList, Stack and Queue in Java?

I am guessing you're confused with the parameterization of the types:

// This works, because there is one class/type definition in the parameterized <> field
ArrayList<String> myArrayList = new ArrayList<String>(); 

// This doesn't work, as you cannot use primitive types here
ArrayList<char> myArrayList = new ArrayList<char>();

How to get line count of a large file cheaply in Python?

How about this one-liner:

file_length = len(open('myfile.txt','r').read().split('\n'))

Takes 0.003 sec using this method to time it on a 3900 line file

def c():
  import time
  s = time.time()
  file_length = len(open('myfile.txt','r').read().split('\n'))
  print time.time() - s

Trim spaces from end of a NSString

This will remove only the trailing characters of your choice.

func trimRight(theString: String, charSet: NSCharacterSet) -> String {

    var newString = theString

    while String(newString.characters.last).rangeOfCharacterFromSet(charSet) != nil {
        newString = String(newString.characters.dropLast())

    return newString

How do you stop tracking a remote branch in Git?

To remove the association between the local and remote branch run:

git config --unset branch.<local-branch-name>.remote
git config --unset branch.<local-branch-name>.merge

Optionally delete the local branch afterwards if you don't need it:

git branch -d <branch>

This won't delete the remote branch.

getting integer values from textfield

You need to use Integer.parseInt(String)

private void jTextField2MouseClicked(java.awt.event.MouseEvent evt) {
            int jml = Integer.parseInt(jTextField3.getText());


How to change language settings in R

If you want to change R's language in terminal to English forever, this works fine for me in macOS:

Open, and say:

touch .bash_profile

Then say:

open -a .bash_profile

These two commands will help you open ".bash_profile" file in TextEdit.

Add this to ".bash_profile" file:

export LANG=en_US.UTF-8

Then save the file, reopen terminal and type R, you will find it's language has changed to english.

If you want language come back to it's original, just simply add a # before export LANG=en_US.UTF-8.

Understanding the results of Execute Explain Plan in Oracle SQL Developer

The CBO builds a decision tree, estimating the costs of each possible execution path available per query. The costs are set by the CPU_cost or I/O_cost parameter set on the instance. And the CBO estimates the costs, as best it can with the existing statistics of the tables and indexes that the query will use. You should not tune your query based on cost alone. Cost allows you to understand WHY the optimizer is doing what it does. Without cost you could figure out why the optimizer chose the plan it did. Lower cost does not mean a faster query. There are cases where this is true and there will be cases where this is wrong. Cost is based on your table stats and if they are wrong the cost is going to be wrong.

When tuning your query, you should take a look at the cardinality and the number of rows of each step. Do they make sense? Is the cardinality the optimizer is assuming correct? Is the rows being return reasonable. If the information present is wrong then its very likely the optimizer doesn't have the proper information it needs to make the right decision. This could be due to stale or missing statistics on the table and index as well as cpu-stats. Its best to have stats updated when tuning a query to get the most out of the optimizer. Knowing your schema is also of great help when tuning. Knowing when the optimizer chose a really bad decision and pointing it in the correct path with a small hint can save a load of time.

Android webview slow

If there's only some few components of your webview that is slow or laggy, try adding this to the elements css:

transform: translate3d(0,0,0);
-webkit-transform: translate3d(0,0,0);

This has been the only speedhack that really had a effect on my webview. But be careful not to overuse it! (you can read more about the hack in this article.)

Back button and refreshing previous activity

If not handling a callback from the editing activity (with onActivityResult), then I'd rather put the logic you mentioned in onStart (or possibly in onRestart), since having it in onResume just seems like overkill, given that changes are only occurring after onStop.

At any rate, be familiar with the Activity lifecycle. Plus, take note of the onRestoreInstanceState and onSaveInstanceState methods, which do not appear in the pretty lifecycle diagram.

(Also, it's worth reviewing how the Notepad Tutorial handles what you're doing, though it does use a database.)

no overload for matches delegate 'system.eventhandler'

You need to change public void klik(PaintEventArgs pea, EventArgs e) to public void klik(object sender, System.EventArgs e) because there is no Click event handler with parameters PaintEventArgs pea, EventArgs e.

How to get SQL from Hibernate Criteria API (*not* for logging)

Here's "another" way to get the SQL :

CriteriaImpl criteriaImpl = (CriteriaImpl)criteria;
SessionImplementor session = criteriaImpl.getSession();
SessionFactoryImplementor factory = session.getFactory();
CriteriaQueryTranslator translator=new CriteriaQueryTranslator(factory,criteriaImpl,criteriaImpl.getEntityOrClassName(),CriteriaQueryTranslator.ROOT_SQL_ALIAS);
String[] implementors = factory.getImplementors( criteriaImpl.getEntityOrClassName() );

CriteriaJoinWalker walker = new CriteriaJoinWalker((OuterJoinLoadable)factory.getEntityPersister(implementors[0]), 
                        session.getLoadQueryInfluencers()   );

String sql=walker.getSQLString();

Filtering Sharepoint Lists on a "Now" or "Today"

Warning about using TODAY (or any calcs in a column).

If you set up a filter and have JUST [Today] it it you should be fine.

But the moment you do something like [Today]-1 ... the view will no longer show up when trying to pick it for alerts.

Another microsoft wonder.

How do I get the AM/PM value from a DateTime?

Something like bool isPM = GetHour() > 11. But if you want to format a date to a string, you shouldn't need to do this yourself. Use the date formatting functions for that.

Swing vs JavaFx for desktop applications

As stated by Oracle, JavaFX is the next step in their Java based rich client strategy. Accordingly, this is what I recommend for your situation:

What would be easier and cleaner to maintain

  • JavaFX has introduced several improvements over Swing, such as, possibility to markup UIs with FXML, and theming with CSS. It has great potential to write a modular, clean & maintainable code.

What would be faster to build from scratch

  • This is highly dependent on your skills and the tools you use.
    • For swing, various IDEs offer tools for rapid development. The best I personally found is the GUI builder in NetBeans.
    • JavaFX has support from various IDEs as well, though not as mature as the support Swing has at the moment. However, its support for markup in FXML & CSS make GUI development on JavaFX intuitive.

MVC Pattern Support

  • JavaFX is very friendly with MVC pattern, and you can cleanly separate your work as: presentation (FXML, CSS), models(Java, domain objects) and logic(Java).
  • IMHO, the MVC support in Swing isn't very appealing. The flow you'll see across various components lacks consistency.

For more info, please take a look these FAQ post by Oracle regarding JavaFX here.

How do I draw a grid onto a plot in Python?

To show a grid line on every tick, add


For example:

import matplotlib.pyplot as plt

points = [
    (0, 10),
    (10, 20),
    (20, 40),
    (60, 100),

x = list(map(lambda x: x[0], points))
y = list(map(lambda x: x[1], points))

plt.scatter(x, y)

enter image description here

In addition, you might want to customize the styling (e.g. solid line instead of dashed line), add:

plt.rc('grid', linestyle="-", color='black')

For example:

import matplotlib.pyplot as plt

points = [
    (0, 10),
    (10, 20),
    (20, 40),
    (60, 100),

x = list(map(lambda x: x[0], points))
y = list(map(lambda x: x[1], points))

plt.rc('grid', linestyle="-", color='black')
plt.scatter(x, y)

enter image description here

Selenium wait until document is ready

This is a working Java version of the example you gave :

void waitForLoad(WebDriver driver) {
    new WebDriverWait(driver, 30).until((ExpectedCondition<Boolean>) wd ->
            ((JavascriptExecutor) wd).executeScript("return document.readyState").equals("complete"));

Example For c#:

public static void WaitForLoad(IWebDriver driver, int timeoutSec = 15)
    IJavaScriptExecutor js = (IJavaScriptExecutor)driver;
    WebDriverWait wait = new WebDriverWait(driver, new TimeSpan(0, 0, timeoutSec));
    wait.Until(wd => js.ExecuteScript("return document.readyState").ToString() == "complete");

Example for PHP:

final public function waitUntilDomReadyState(RemoteWebDriver $webDriver): void
    $webDriver->wait()->until(function () {
        return $webDriver->executeScript('return document.readyState') === 'complete';

How to highlight text using javascript

Since HTML5 you can use the <mark></mark> tags to highlight text. You can use javascript to wrap some text/keyword between these tags. Here is a little example of how to mark and unmark text.