Programs & Examples On #Routines

curl: (35) error:1408F10B:SSL routines:ssl3_get_record:wrong version number

* Uses proxy env variable http_proxy == ''   

The https:// is wrong, it should be http://. The proxy itself should be accessed by HTTP and not HTTPS even though the target URL is HTTPS. The proxy will nevertheless properly handle HTTPS connection and keep the end-to-end encryption. See HTTP CONNECT method for details how this is done.

Read file from resources folder in Spring Boot

Below is my working code.

List<sampleObject> list = new ArrayList<>();
File file = new ClassPathResource("json/test.json").getFile();
ObjectMapper objectMapper = new ObjectMapper();
sampleObject = Arrays.asList(objectMapper.readValue(file, sampleObject[].class));

Hope it helps one!

Solving sslv3 alert handshake failure when trying to use a client certificate

What SSL private key should be sent along with the client certificate?

None of them :)

One of the appealing things about client certificates is it does not do dumb things, like transmit a secret (like a password), in the plain text to a server (HTTP basic_auth). The password is still used to unlock the key for the client certificate, its just not used directly to during exchange or tp authenticate the client.

Instead, the client chooses a temporary, random key for that session. The client then signs the temporary, random key with his cert and sends it to the server (some hand waiving). If a bad guy intercepts anything, its random so it can't be used in the future. It can't even be used for a second run of the protocol with the server because the server will select a new, random value, too.

Fails with: error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure

Use TLS 1.0 and above; and use Server Name Indication.

You have not provided any code, so its not clear to me how to tell you what to do. Instead, here's the OpenSSL command line to test it:

openssl s_client -connect -tls1 -servername \
    -cert mycert.pem -key mykey.pem -CAfile <certificate-authority-for-service>.pem

You can also use -CAfile to avoid the “verify error:num=20”. See, for example, “verify error:num=20” when connecting to

Docker: unable to prepare context: unable to evaluate symlinks in Dockerfile path: GetFileAttributesEx

I tried this and it worked:

$ docker build -t test_dotnet_image 

Please see quotes+un-quotes around the foldername.

Note: In Folder "C:\Users\ssundarababu\Documents\Docker\Learn\SimpleDockerfile" I have my Dockerfile.

How to resolve the "EVP_DecryptFInal_ex: bad decrypt" during file decryption

Errors: "Bad encrypt / decrypt" "gitencrypt_smudge: FAILURE: openssl error decrypting file"

There are various error strings that are thrown from openssl, depending on respective versions, and scenarios. Below is the checklist I use in case of openssl related issues:

  1. Ideally, openssl is able to encrypt/decrypt using same key (+ salt) & enc algo only.
  2. Ensure that openssl versions (used to encrypt/decrypt), are compatible. For eg. the hash used in openssl changed at version 1.1.0 from MD5 to SHA256. This produces a different key from the same password. Fix: add "-md md5" in 1.1.0 to decrypt data from lower versions, and add "-md sha256 in lower versions to decrypt data from 1.1.0

  3. Ensure that there is a single openssl version installed in your machine. In case there are multiple versions installed simultaneously (in my machine, these were installed :- 'LibreSSL 2.6.5' and 'openssl 1.1.1d'), make the sure that only the desired one appears in your PATH variable.

SSL error SSL3_GET_SERVER_CERTIFICATE:certificate verify failed

In my case, I was on CentOS 7 and my php installation was pointing to a certificate that was being generated through update-ca-trust. The symlink was /etc/pki/tls/cert.pem pointing to /etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem. This was just a test server and I wanted my self signed cert to work properly. So in my case...

# My root ca-trust folder was here. I coped the .crt file to this location
# and renamed it to a .pem

# Then run this command and it will regenerate the certs for you and
# include your self signed cert file.

Then some of my api calls started working as my cert was now trusted. Also if your ca-trust gets updated through yum or something, this will rebuild your root certificates and still include your self signed cert. Run man update-ca-trust for more info on what to do and how to do it. :)

Can't get private key with openssl (no start line:pem_lib.c:703:Expecting: ANY PRIVATE KEY)

It looks like you have a certificate in DER format instead of PEM. This is why it works correctly when you provide the -inform PEM command line argument (which tells openssl what input format to expect).

It's likely that your private key is using the same encoding. It looks as if the openssl rsa command also accepts a -inform argument, so try:

openssl rsa -text -in file.key -inform DER

A PEM encoded file is a plain-text encoding that looks something like:


While DER is a binary encoding format.


Sometimes keys are distributed in PKCS#8 format (which can be either PEM or DER encoded). Try this and see what you get:

openssl pkcs8 -in file.key -inform der

wget ssl alert handshake failure

I was in SLES12 and for me it worked after upgrading to wget 1.14, using --secure-protocol=TLSv1.2 and using --auth-no-challenge.

wget --no-check-certificate --secure-protocol=TLSv1.2 --user=satul --password=xxx --auth-no-challenge -v --debug https://jenkins-server/artifact/build.x86_64.tgz

how to fix stream_socket_enable_crypto(): SSL operation failed with code 1

edit your .env and add this line after mail config lines


Save and try to send email

How to get Python requests to trust a self signed SSL certificate?

You may try:

settings = s.merge_environment_settings(prepped.url, None, None, None, None)

You can read more here:

Shift elements in a numpy array

For those who want to just copy and paste the fastest implementation of shift, there is a benchmark and conclusion(see the end). In addition, I introduce fill_value parameter and fix some bugs.


import numpy as np
import timeit

# enhanced from IronManMark20 version
def shift1(arr, num, fill_value=np.nan):
    arr = np.roll(arr,num)
    if num < 0:
        arr[num:] = fill_value
    elif num > 0:
        arr[:num] = fill_value
    return arr

# use np.roll and np.put by IronManMark20
def shift2(arr,num):
    if num<0:
    elif num > 0:
    return arr

# use np.pad and slice by me.
def shift3(arr, num, fill_value=np.nan):
    l = len(arr)
    if num < 0:
        arr = np.pad(arr, (0, abs(num)), mode='constant', constant_values=(fill_value,))[:-num]
    elif num > 0:
        arr = np.pad(arr, (num, 0), mode='constant', constant_values=(fill_value,))[:-num]

    return arr

# use np.concatenate and np.full by chrisaycock
def shift4(arr, num, fill_value=np.nan):
    if num >= 0:
        return np.concatenate((np.full(num, fill_value), arr[:-num]))
        return np.concatenate((arr[-num:], np.full(-num, fill_value)))

# preallocate empty array and assign slice by chrisaycock
def shift5(arr, num, fill_value=np.nan):
    result = np.empty_like(arr)
    if num > 0:
        result[:num] = fill_value
        result[num:] = arr[:-num]
    elif num < 0:
        result[num:] = fill_value
        result[:num] = arr[-num:]
        result[:] = arr
    return result

arr = np.arange(2000).astype(float)

def benchmark_shift1():
    shift1(arr, 3)

def benchmark_shift2():
    shift2(arr, 3)

def benchmark_shift3():
    shift3(arr, 3)

def benchmark_shift4():
    shift4(arr, 3)

def benchmark_shift5():
    shift5(arr, 3)

benchmark_set = ['benchmark_shift1', 'benchmark_shift2', 'benchmark_shift3', 'benchmark_shift4', 'benchmark_shift5']

for x in benchmark_set:
    number = 10000
    t = timeit.timeit('%s()' % x, 'from __main__ import %s' % x, number=number)
    print '%s time: %f' % (x, t)

benchmark result:

benchmark_shift1 time: 0.265238
benchmark_shift2 time: 0.285175
benchmark_shift3 time: 0.473890
benchmark_shift4 time: 0.099049
benchmark_shift5 time: 0.052836


shift5 is winner! It's OP's third solution.

TLS 1.2 not working in cURL

TLS 1.1 and TLS 1.2 are supported since OpenSSL 1.0.1

Forcing TLS 1.1 and 1.2 are only supported since curl 7.34.0

You should consider an upgrade. SSL handshake aborted: Failure in SSL library, usually a protocol error

My Answer is close to the above answers but you need to write the class exactly without changing anything.

public class TLSSocketFactory extends SSLSocketFactory {

private SSLSocketFactory delegate;

public TLSSocketFactory() throws KeyManagementException, NoSuchAlgorithmException {
    SSLContext context = SSLContext.getInstance("TLS");
    context.init(null, null, null);
    delegate = context.getSocketFactory();

public String[] getDefaultCipherSuites() {
    return delegate.getDefaultCipherSuites();

public String[] getSupportedCipherSuites() {
    return delegate.getSupportedCipherSuites();

public Socket createSocket() throws IOException {
    return enableTLSOnSocket(delegate.createSocket());

public Socket createSocket(Socket s, String host, int port, boolean autoClose) throws IOException {
    return enableTLSOnSocket(delegate.createSocket(s, host, port, autoClose));

public Socket createSocket(String host, int port) throws IOException, UnknownHostException {
    return enableTLSOnSocket(delegate.createSocket(host, port));

public Socket createSocket(String host, int port, InetAddress localHost, int localPort) throws IOException, UnknownHostException {
    return enableTLSOnSocket(delegate.createSocket(host, port, localHost, localPort));

public Socket createSocket(InetAddress host, int port) throws IOException {
    return enableTLSOnSocket(delegate.createSocket(host, port));

public Socket createSocket(InetAddress address, int port, InetAddress localAddress, int localPort) throws IOException {
    return enableTLSOnSocket(delegate.createSocket(address, port, localAddress, localPort));

private Socket enableTLSOnSocket(Socket socket) {
    if(socket != null && (socket instanceof SSLSocket)) {
        ((SSLSocket)socket).setEnabledProtocols(new String[] {"TLSv1.1", "TLSv1.2"});
    return socket;


and to use it with HttpsURLConnection

HttpsURLConnection  conn = (HttpsURLConnection) url.openConnection();

int sdk = android.os.Build.VERSION.SDK_INT;
            if (sdk < Build.VERSION_CODES.LOLLIPOP) {
                if (url.toString().startsWith("https")) {
                    try {
                        TLSSocketFactory sc = new TLSSocketFactory();
                    } catch (Exception e) {
                        String sss = e.toString();

How to enable TLS 1.2 support in an Android application (running on Android 4.1 JB)

Add play-services-safetynet library in android build.gradle:

implementation ''

and add this code to your

  public void onCreate() {
    SoLoader.init(this, /* native exopackage */ false);

  private void upgradeSecurityProvider() {
    ProviderInstaller.installIfNeededAsync(this, new ProviderInstallListener() {
      public void onProviderInstalled() {


      public void onProviderInstallFailed(int errorCode, Intent recoveryIntent) {
//        GooglePlayServicesUtil.showErrorNotification(errorCode, MainApplication.this);
        GoogleApiAvailability.getInstance().showErrorNotification(MainApplication.this, errorCode);

SSL: error:0B080074:x509 certificate routines:X509_check_private_key:key values mismatch

This can also happen when your CA issues an intermediate cert

I ran into this issue (twice) with nginx and none of the solutions in this post explained the issue. The blog post here by a nice gentleman named Marco nailed it, and I am pasting it here for anyone who also runs into what I was seeing.

In my case, go-daddy was the CA and this is specific to how they issue the cert and the intermediate cert bundles.

Here is the excerpt from Marco's blog post

With Nginx, if your CA included an intermediate certificate, you must create a single chained certificate file that contains your certificate and the CA’s intermediate certificates.

You can use this command to create a combined file called

cat intermediate.crt >

file_get_contents(): SSL operation failed with code 1, Failed to enable crypto

At first you need to have enabled curl extension in PHP. Then you can use this function:

function file_get_contents_ssl($url) {
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
    curl_setopt($ch, CURLOPT_HEADER, false);
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_REFERER, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
    curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 3000); // 3 sec.
    curl_setopt($ch, CURLOPT_TIMEOUT, 10000); // 10 sec.
    $result = curl_exec($ch);
    return $result;

It works similar to function file_get_contents(..).


echo file_get_contents_ssl("");


<!doctype html>
    <title>Example Domain</title>

docker error: /var/run/docker.sock: no such file or directory

You don't need to run any docker commands as sudo when you're using boot2docker as every command passed into the boot2docker VM runs as root by default.

You're seeing the error when you're running as sudo because sudo doesn't have the DOCKER_HOST env set, only your user does.

You can confirm this by doing a:

$ env

Then a

$ sudo env

And looking for DOCKER_HOST in each output.

As for having a docker file that runs your script, something like this might work for you:


FROM busybox

# Copy your script into the docker image
ADD /path/to/your/ /usr/local/bin/

# Run your script
CMD /usr/local/bin/

Then you can run:

docker build -t your-image-name:your-tag .

This will build your docker image, which you can see by doing a:

docker images

Then, to run your container, you can do a:

docker run your-image-name:your-tag

This run command will start a container from the image you created with your Dockerfile and your build command and then it will finish once your has finished executing.

Why am I getting a "401 Unauthorized" error in Maven?

I got the same error when trying to deploy to a Artifactory repository, the following solved the issue for me:

Go to the repository setting in artifactory and enable the point "Force Maven Authentication" and the 401 "Unauthorized" error should be gone. (Of course you need to supply your credentials in the settings.xml file at best in plain text to prevent issues)

I guess by default, even through you supply the right credentials in the settings.xml file, they don't get used and you get the Unauthorized exception.

OpenSSL Command to check if a server is presenting a certificate

I was getting the below as well trying to get out to as our proxy re-writes the HTTPS connection with their self-signed cert:

no peer certificate available No client certificate CA names sent

In my output there was also:

Protocol : TLSv1.3

I added -tls1_2 and it worked fine and now I can see which CA it is using on the outgoing request. e.g.:
openssl s_client -connect -tls1_2

Node.js https pem error: routines:PEM_read_bio:no start line

Was facing the same problem In my case I changed the option parameter of cert to pfx & removed utf8 encoding.


var options = {
    hostname : 'localhost',
    path : '/',
    method : 'POST',
    cert: fs.readFileSync(testCert, 'utf8'),


var options = {
    hostname : 'localhost',
    path : '/',
    method : 'POST',
    pfx: fs.readFileSync(testCert),

Java 8 Streams FlatMap method example

This method takes one Function as an argument, this function accepts one parameter T as an input argument and return one stream of parameter R as a return value. When this function is applied on each element of this stream, it produces a stream of new values. All the elements of these new streams generated by each element are then copied to a new stream, which will be a return value of this method.

Generate random array of floats between a range

np.random.random_sample(size) will generate random floats in the half-open interval [0.0, 1.0).

OpenSSL: PEM routines:PEM_read_bio:no start line:pem_lib.c:703:Expecting: TRUSTED CERTIFICATE

I had the same issue using Windows, got if fixed by opening it in Notepad++ and changing the encoding from "UCS-2 LE BOM" to "UTF-8".

Unable to load Private Key. (PEM routines:PEM_read_bio:no start line:pem_lib.c:648:Expecting: ANY PRIVATE KEY)

I changed the header and footer of the PEM file to




Finally, it works!

How to multiply duration by integer?

In Go, you can multiply variables of same type, so you need to have both parts of the expression the same type.

The simplest thing you can do is casting an integer to duration before multiplying, but that would violate unit semantics. What would be multiplication of duration by duration in term of units?

I'd rather convert time.Millisecond to an int64, and then multiply it by the number of milliseconds, then cast to time.Duration:

time.Duration(int64(time.Millisecond) * int64(rand.Int31n(1000)))

This way any part of the expression can be said to have a meaningful value according to its type. int64(time.Millisecond) part is just a dimensionless value - the number of smallest units of time in the original value.

If walk a slightly simpler path:

time.Duration(rand.Int31n(1000)) * time.Millisecond

The left part of multiplication is nonsense - a value of type "time.Duration", holding something irrelevant to its type:

numberOfMilliseconds := 100
// just can't come up with a name for following:
someLHS := time.Duration(numberOfMilliseconds)

And it's not just semantics, there is actual functionality associated with types. This code prints:


Interestingly, the code sample here uses the simplest code, with the same misleading semantics of Duration conversion:

seconds := 10

fmt.Print(time.Duration(seconds)*time.Second) // prints 10s

Error LNK2019: Unresolved External Symbol in Visual Studio

When you have everything #included, an unresolved external symbol is often a missing * or & in the declaration or definition of a function.

openssl s_client -cert: Proving a client certificate was sent to the server

In order to verify a client certificate is being sent to the server, you need to analyze the output from the combination of the -state and -debug flags.

First as a baseline, try running

$ openssl s_client -connect host:443 -state -debug

You'll get a ton of output, but the lines we are interested in look like this:

SSL_connect:SSLv3 read server done A
write to 0x211efb0 [0x21ced50] (12 bytes => 12 (0xC))
0000 - 16 03 01 00 07 0b 00 00-03                        .........
000c - <SPACES/NULS>
SSL_connect:SSLv3 write client certificate A

What's happening here:

  • The -state flag is responsible for displaying the end of the previous section:

    SSL_connect:SSLv3 read server done A  

    This is only important for helping you find your place in the output.

  • Then the -debug flag is showing the raw bytes being sent in the next step:

    write to 0x211efb0 [0x21ced50] (12 bytes => 12 (0xC))
    0000 - 16 03 01 00 07 0b 00 00-03                        .........
    000c - <SPACES/NULS>
  • Finally, the -state flag is once again reporting the result of the step that -debug just echoed:

    SSL_connect:SSLv3 write client certificate A

So in other words: s_client finished reading data sent from the server, and sent 12 bytes to the server as (what I assume is) a "no client certificate" message.

If you repeat the test, but this time include the -cert and -key flags like this:

$ openssl s_client -connect host:443 \
   -cert cert_and_key.pem \
   -key cert_and_key.pem  \
   -state -debug

your output between the "read server done" line and the "write client certificate" line will be much longer, representing the binary form of your client certificate:

SSL_connect:SSLv3 read server done A
write to 0x7bd970 [0x86d890] (1576 bytes => 1576 (0x628))
0000 - 16 03 01 06 23 0b 00 06-1f 00 06 1c 00 06 19 31   ....#..........1
0620 - 95 ca 5e f4 2f 6c 43 11-                          ..^%/lC.
SSL_connect:SSLv3 write client certificate A

The 1576 bytes is an excellent indication on its own that the cert was transmitted, but on top of that, the right-hand column will show parts of the certificate that are human-readable: You should be able to recognize the CN and issuer strings of your cert in there.

SSL error : routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed

could also happen when your local time is off (e.g. before certificate validation time), this was the case in my error...

pip issue installing almost any library

I solved this issue with the following steps (on sles 11sp2)

zypper remove pip
easy_install pip=1.2.1
pip install --upgrade scons

Here are the same steps in puppet (which should work on all distros)

  package { 'python-pip':
    ensure => absent,
  exec { 'python-pip':
    command  => '/usr/bin/easy_install pip==1.2.1',
    require  => Package['python-pip'],
  package { 'scons': 
    ensure   => latest,
    provider => pip,
    require  => Exec['python-pip'],

How to check a channel is closed or not without reading it?

it's easier to check first if the channel has elements, that would ensure the channel is alive.

func isChanClosed(ch chan interface{}) bool {
    if len(ch) == 0 {
        select {
        case _, ok := <-ch:
            return !ok
    return false 

node-request - Getting error "SSL23_GET_SERVER_HELLO:unknown protocol"

This was totally my bad.

I was using standard node http.request on a part of the code which should be sending requests to only http adresses. Seems like the db had a single https address which was queried with a random interval.

Simply, I was trying to send a http request to https.

How to correctly save instance state of Fragments in back stack?

On the latest support library none of the solutions discussed here are necessary anymore. You can play with your Activity's fragments as you like using the FragmentTransaction. Just make sure that your fragments can be identified either with an id or tag.

The fragments will be restored automatically as long as you don't try to recreate them on every call to onCreate(). Instead, you should check if savedInstanceState is not null and find the old references to the created fragments in this case.

Here is an example:

protected void onCreate(Bundle savedInstanceState) {

    if (savedInstanceState == null) {
        myFragment = MyFragment.newInstance();
                .add(, myFragment, MY_FRAGMENT_TAG)
    } else {
        myFragment = (MyFragment) getSupportFragmentManager()

Note however that there is currently a bug when restoring the hidden state of a fragment. If you are hiding fragments in your activity, you will need to restore this state manually in this case.

Unable to establish SSL connection, how do I fix my SSL cert?

This problem happened for me only in special cases, when I called website from some internet providers,

I've configured only ip v4 in VirtualHost configuration of apache, but some of router use ip v6, and when I added ip v6 to apache config the problem solved.

Python Requests requests.exceptions.SSLError: [Errno 8] _ssl.c:504: EOF occurred in violation of protocol

Reposting this here for others from the requests issue page:

Requests' does not support doing this before version 1. Subsequent to version 1, you are expected to subclass the HTTPAdapter, like so:

from requests.adapters import HTTPAdapter
from requests.packages.urllib3.poolmanager import PoolManager
import ssl

class MyAdapter(HTTPAdapter):
    def init_poolmanager(self, connections, maxsize, block=False):
        self.poolmanager = PoolManager(num_pools=connections,

When you've done that, you can do this:

import requests
s = requests.Session()
s.mount('https://', MyAdapter())

Any request through that session object will then use TLSv1.

PIL image to array (numpy array to array) - Python

I highly recommend you use the tobytes function of the Image object. After some timing checks this is much more efficient.

def jpg_image_to_array(image_path):
  Loads JPEG image into 3D Numpy array of shape 
  (width, height, channels)
  with as image:         
    im_arr = np.fromstring(image.tobytes(), dtype=np.uint8)
    im_arr = im_arr.reshape((image.size[1], image.size[0], 3))                                   
  return im_arr

The timings I ran on my laptop show

In [76]: %timeit np.fromstring(im.tobytes(), dtype=np.uint8)
1000 loops, best of 3: 230 µs per loop

In [77]: %timeit np.array(im.getdata(), dtype=np.uint8)
10 loops, best of 3: 114 ms per loop


Python Requests throwing SSLError

I encountered the same issue and ssl certificate verify failed issue when using aws boto3, by review boto3 code, I found the REQUESTS_CA_BUNDLE is not set, so I fixed the both issue by setting it manually:

from boto3.session import Session
import os

# debian
os.environ['REQUESTS_CA_BUNDLE'] = os.path.join(
# centos
#   'ca-bundle.crt')

For aws-cli, I guess setting REQUESTS_CA_BUNDLE in ~/.bashrc will fix this issue (not tested because my aws-cli works without it).

REQUESTS_CA_BUNDLE=/etc/ssl/certs/ca-certificates.crt # ca-bundle.crt

https connection using CURL from command line

You need to provide the entire certificate chain to curl, since curl no longer ships with any CA certs. Since the cacert option can only use one file, you need to concat the full chain info into 1 file

Copy the certificate chain (from your browser, for example) into DER encoded binary x.509(.cer). Do this for each cert.

Convert the certs into PEM, and concat them into 1 file.

openssl x509 -inform DES -in file1.cer -out file1.pem -text
openssl x509 -inform DES -in file2.cer -out file2.pem -text
openssl x509 -inform DES -in file3.cer -out file3.pem -text

cat *.pem > certRepo

curl --cacert certRepo -u user:passwd -X GET -H 'Content-Type: application/json' "https//"

I wrote a blog on how to do this here:

In practice, what are the main uses for the new "yield from" syntax in Python 3.3?

In applied usage for the Asynchronous IO coroutine, yield from has a similar behavior as await in a coroutine function. Both of which is used to suspend the execution of coroutine.

For Asyncio, if there's no need to support an older Python version (i.e. >3.5), async def/await is the recommended syntax to define a coroutine. Thus yield from is no longer needed in a coroutine.

But in general outside of asyncio, yield from <sub-generator> has still some other usage in iterating the sub-generator as mentioned in the earlier answer.

Use of True, False, and None as return values in Python functions

One thing to ensure is that nothing can reassign your variable. If it is not a Boolean in the end, relying on truthiness will lead to bugs. The beauty of conditional programming in dynamically typed languages :).

The following prints "no".

x = False
if x:
    print 'yes'
    print 'no'

Now let's change x.

x = 'False'

Now the statement prints "yes", because the string is truthy.

if x:
    print 'yes'
    print 'no'

This statement, however, correctly outputs "no".

if x == True:
    print 'yes'
    print 'no'

Convert PEM traditional private key to PKCS8 private key

To convert the private key from PKCS#1 to PKCS#8 with openssl:

# openssl pkcs8 -topk8 -inform PEM -outform PEM -nocrypt -in pkcs1.key -out pkcs8.key

That will work as long as you have the PKCS#1 key in PEM (text format) as described in the question.

Using openssl to get the certificate from a server

The easiest command line for this, which includes the PEM output to add it to the keystore, as well as a human readable output and also supports SNI, which is important if you are working with an HTTP server is:

openssl s_client -servername -connect \
    </dev/null 2>/dev/null | openssl x509 -text

The -servername option is to enable SNI support and the openssl x509 -text prints the certificate in human readable format.

OpenSSL and error in reading openssl.conf file

  1. first, make sure you have an openssl.cnf file in the right path;
  2. if you can't find it, just download one and copy it to your setting path.

$ set OPENSSL_CONF=C:\OpenSSL\bin\openssl.cnf

How to encrypt a large file in openssl using public key

I found the instructions at useful.

To paraphrase the linked site with filenames from your example:

Generate a symmetric key because you can encrypt large files with it

openssl rand -base64 32 > key.bin

Encrypt the large file using the symmetric key

openssl enc -aes-256-cbc -salt -in myLargeFile.xml \
  -out myLargeFile.xml.enc -pass file:./key.bin

Encrypt the symmetric key so you can safely send it to the other person

openssl rsautl -encrypt -inkey public.pem -pubin -in key.bin -out key.bin.enc

Destroy the un-encrypted symmetric key so nobody finds it

shred -u key.bin

At this point, you send the encrypted symmetric key (key.bin.enc) and the encrypted large file (myLargeFile.xml.enc) to the other person

The other person can then decrypt the symmetric key with their private key using

openssl rsautl -decrypt -inkey private.pem -in key.bin.enc -out key.bin

Now they can use the symmetric key to decrypt the file

openssl enc -d -aes-256-cbc -in myLargeFile.xml.enc \
  -out myLargeFile.xml -pass file:./key.bin

And you're done. The other person has the decrypted file and it was safely sent.

JUnit Testing private variables?

First of all, you are in a bad position now - having the task of writing tests for the code you did not originally create and without any changes - nightmare! Talk to your boss and explain, it is not possible to test the code without making it "testable". To make code testable you usually do some important changes;

Regarding private variables. You actually never should do that. Aiming to test private variables is the first sign that something wrong with the current design. Private variables are part of the implementation, tests should focus on behavior rather of implementation details.

Sometimes, private field are exposed to public access with some getter. I do that, but try to avoid as much as possible (mark in comments, like 'used for testing').

Since you have no possibility to change the code, I don't see possibility (I mean real possibility, not like Reflection hacks etc.) to check private variable.

HTTPS and SSL3_GET_SERVER_CERTIFICATE:certificate verify failed, CA is OK

I have the same error on amazon AMI linux.

I Solved by setting curl.cainfo on /etc/php.d/curl.ini

Addition October 2018

On Amazon Linux v1 edit this file

vi /etc/php.d/20-curl.ini

To add this line


Auto Scale TextView Text to Fit within Bounds

Warning, bug in Android Honeycomb and Ice Cream Sandwich

Androids versions: 3.1 - 4.04 have a bug, that setTextSize() inside of TextView works only for the 1st time (1st invocation).

Bug is described here:

workaround is to add new line character to text assigned to TextView before changing size:

final String DOUBLE_BYTE_SPACE = "\u3000";

I use it in my code as follow:

final String DOUBLE_BYTE_SPACE = "\u3000";
AutoResizeTextView textView = (AutoResizeTextView) view.findViewById(;
String fixString = "";
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.HONEYCOMB_MR1
   && android.os.Build.VERSION.SDK_INT <= android.os.Build.VERSION_CODES.ICE_CREAM_SANDWICH_MR1) {  
    fixString = DOUBLE_BYTE_SPACE;
textView.setText(fixString + "The text" + fixString);

I add this "\u3000" character on left and right of my text, to keep it centered. If you have it aligned to left then append to the right only. Of course it can be also embedded with AutoResizeTextView widget, but I wanted to keep fix code outside.

SSL certificate rejected trying to access GitHub over HTTPS behind firewall

Try using a .netrc file, it will authenticate over https. Create a file call .netrc in your home directory and put this in it:

machine login myusername password mypass

See this post for more info:

Excel tab sheet names vs. Visual Basic sheet names

There are (at least) two different ways to get to theWorksheet object

  • via the Sheets or Worksheets collections as referenced by DanM
  • by unqualified object names

When a new workbook with three worksheets is created there will exist four objects which you can access via unqualified names: ThisWorkbook; Sheet1; Sheet2; Sheet3. This lets you write things like this:

Sheet1.Range("A1").Value = "foo"

Although this may seem like a useful shortcut, the problem comes when the worksheets are renamed. The unqualified object name remains as Sheet1 even if the worksheet is renamed to something totally different.

There is some logic to this because:

  • worksheet names don't conform to the same rules as variable names
  • you might accidentally mask an existing variable

For example (tested in Excel 2003), create a new Workbook with three worksheets. Create two modules. In one module declare this:

Public Sheet4 As Integer

In the other module put:

Sub main()

Sheet4 = 4

MsgBox Sheet4

End Sub

Run this and the message box should appear correctly.

Now add a fourth worksheet to the workbook which will create a Sheet4 object. Try running main again and this time you will get an "Object does not support this property or method" error

How does C compute sin() and other math functions?

Functions like sine and cosine are implemented in microcode inside microprocessors. Intel chips, for example, have assembly instructions for these. A C compiler will generate code that calls these assembly instructions. (By contrast, a Java compiler will not. Java evaluates trig functions in software rather than hardware, and so it runs much slower.)

Chips do not use Taylor series to compute trig functions, at least not entirely. First of all they use CORDIC, but they may also use a short Taylor series to polish up the result of CORDIC or for special cases such as computing sine with high relative accuracy for very small angles. For more explanation, see this StackOverflow answer.

How to asynchronously call a method in Java

There is also nice library for Async-Await created by EA:

From their Readme:

With EA Async

import static com.ea.async.Async.await;
import static java.util.concurrent.CompletableFuture.completedFuture;

public class Store
    public CompletableFuture<Boolean> buyItem(String itemTypeId, int cost)
        if(!await(bank.decrement(cost))) {
            return completedFuture(false);
        return completedFuture(true);

Without EA Async

import static java.util.concurrent.CompletableFuture.completedFuture;

public class Store
    public CompletableFuture<Boolean> buyItem(String itemTypeId, int cost)
        return bank.decrement(cost)
            .thenCompose(result -> {
                if(!result) {
                    return completedFuture(false);
                return inventory.giveItem(itemTypeId).thenApply(res -> true);

How should I validate an e-mail address?

You could also use

InternetAddress emailAddr = new InternetAddress(email);

If the email is not valid it will throw an AddressException.

Unfortunately Android doesn't support jndi-dns, but just to give you an idea of a more powerful email validation, you could use it to validate the email domain. Maybe an Android guru could help and show if there are similar alternatives... An example implementation with "regular" java is available here.


I just realized that javax.mail isn't support neither... But this post shows a workaround.

Sending email with gmail smtp with codeigniter email library

You need to enable SSL in your PHP config. Load up php.ini and find a line with the following:


Uncomment it. :D

(by removing the semicolon from the statement)


What is the best Java email address validation method?

You may also want to check for the length - emails are a maximum of 254 chars long. I use the apache commons validator and it doesn't check for this.

Performance of Java matrix math libraries?

Building on Varkhan's post that Pentium-specific native code would do better:

How can I check for Python version in a program that uses new language features?

The problem is quite simple. You checked if the version was less than 2.4, not less than or equal to. So if the Python version is 2.4, it's not less than 2.4. What you should have had was:

    if sys.version_info **<=** (2, 4):

, not

    if sys.version_info < (2, 4):

Invoking JavaScript code in an iframe from the parent page

       $("#myframe").load(function() {

How many parameters are too many?

If I have 7-10 parameters in one routine I look at bundling them into a new class but not if that class would be nothing but a bunch of fields with getters and setters - the new class has to do something other than shuffle values in and out. Otherwise I'd rather put up with the long parameter list.

How to create a GUID / UUID

Simple code that uses crypto.getRandomValues(a) on supported browsers (IE11+, iOS7+, FF21+, Chrome, Android Chrome). Avoids using Math.random() because that can cause collisions (for example 20 collisions for 4000 generated uuids in a real situation by Muxa).

function uuid() {
    function randomDigit() {
        if (crypto && crypto.getRandomValues) {
            var rands = new Uint8Array(1);
            return (rands[0] % 16).toString(16);
        } else {
            return ((Math.random() * 16) | 0).toString(16);
    var crypto = window.crypto || window.msCrypto;
    return 'xxxxxxxx-xxxx-4xxx-8xxx-xxxxxxxxxxxx'.replace(/x/g, randomDigit);


  • Optimised for code readability not speed, so suitable for say a few hundred uuid's per second. Generates about 10000 uuid() per second in Chromium on my laptop using to measure performance.
  • Only uses 8 for "y" because that simplifies code readability (y is allowed to be 8, 9, A or B).

Install Android App Bundle on device

For MAC:

brew install bundletool
bundletool build-apks --bundle=./app.aab --output=./app.apks
bundletool install-apks --apks=app.apks

Failed to load resource 404 (Not Found) - file location error?

Looks like the path you gave doesn't have any bootstrap files in them.


Make sure the files exist over there , else point the files to the correct path, which should be in your case


How to use pip with python 3.4 on windows?

Usage of pip for installation of packages in Python 3

Step 1: Install Python 3. Yes, by default an application file pip3.exe is already located there in the path (E.g.):


Step 2: Go to

>Control Panel (Local Machine) > System > Advanced system settings >

>Click on `Environment Variables` >
Set a New User Variable, for this click `New` >
Write new 'Variable name' as "PYTHON_SCRIPTS" >
Copy that path of `pip3.exe` and paste within variable value > `OK` >

>Below again find out and click on `Path` under 'system variables' >
Edit this path >
Within 'Variable value' append and paste the same path of `pip3.exe` after putting a ';' >
Click `OK`/`Apply` and come out.

Step 3: Now, open cmd bash/shell by Pressing key Windows+R.

> Write 'pip3' and press 'Enter'. If pip3 is recognized you can go ahead.

Step 4: In this same cmd

> Write path of the `pip3.exe` followed by `/pip install 'package name'`

As Example just write:

C:/Users/name/AppData/Local/Programs/Python/Python36-32/Scripts/pip install matplotlib

Press Enter now. The Package matplotlib will start getting downloaded.

Further, for upgrading any package

Open cmd bash/shell again, then

type that path of pip3.exe followed by /pip install --upgrade 'package name' Press Enter.

As Example just write:

C:/Users/name/AppData/Local/Programs/Python/Python36-32/Scripts/pip install --upgrade matplotlib

Upgrading of the package will start :)

nodemon command is not recognized in terminal for node js server

I tried installing the nodemon globally but that doesn't worked for me. whenever i try to run it always shows me the error:

nodemon : The term 'nodemon' is not recognized as the name of a
cmdlet, function, script file, or operable program. Check the spelling
of the name, or if a path was included, verify that the path is
correct and try again.

2. I have found two solutions for this

solution 1:

What i have tried is to update the "scripts" in package.json file and there i have added

"server": "nodemon app.js"

above line of code and after that

npm run server

Soluton 2:

  1. Press the Windows key.

  2. Type "Path" in the search box and select "Edit the system environment variables"

  3. Click on "Environment Variables" near the bottom.

  4. In the "System Variables" section double click on the "Path" variable.

  5. Click "New" on the right-hand side.

  6. Copy and paste this into the box (replace [Username]):


  1. restart your terminal and VSCode.

  2. Then type nodemon app.js to run the nodemon

i applied solution 2 as we just need to run nodemon [filename.js]

Convert DataTable to List<T>

please try this code:

public List<T> ConvertToList<T>(DataTable dt)
    var columnNames = dt.Columns.Cast<DataColumn>()
        .Select(c => c.ColumnName)
    var properties = typeof(T).GetProperties();
    return dt.AsEnumerable().Select(row =>
        var objT = Activator.CreateInstance<T>();
        foreach (var pro in properties)
            if (columnNames.Contains(pro.Name))
                pro.SetValue(objT, row[pro.Name]);
        return objT;

What is the difference between a HashMap and a TreeMap?

TreeMap is an example of a SortedMap, which means that the order of the keys can be sorted, and when iterating over the keys, you can expect that they will be in order.

HashMap on the other hand, makes no such guarantee. Therefore, when iterating over the keys of a HashMap, you can't be sure what order they will be in.

HashMap will be more efficient in general, so use it whenever you don't care about the order of the keys.

How to skip to next iteration in jQuery.each() util?

What they mean by non-false is:

return true;

So this code:

var arr = ["one", "two", "three", "four", "five"];_x000D_
$.each(arr, function(i) {_x000D_
  if (arr[i] == 'three') {_x000D_
    return true;_x000D_
<script src=""></script>

will log one, two, four, five.

Delete cookie by name?

In my case I used blow code for different environment.

  document.cookie = name +`=; Path=/; Expires=Thu, 01 Jan 1970 00:00:01 GMT;Domain=.${document.domain.split('.').splice(1).join('.')}`;

Replace deprecated preg_replace /e with preg_replace_callback

You can use an anonymous function to pass the matches to your function:

$result = preg_replace_callback(
    function($m) { return CallFunction($m[1], $m[2], $m[3], $m[4], $m[5]); },

Apart from being faster, this will also properly handle double quotes in your string. Your current code using /e would convert a double quote " into \".

How to do a https request with bad certificate?

All of these answers are wrong! Do not use InsecureSkipVerify to deal with a CN that doesn't match the hostname. The Go developers unwisely were adamant about not disabling hostname checks (which has legitimate uses - tunnels, nats, shared cluster certs, etc), while also having something that looks similar but actually completely ignores the certificate check. You need to know that the certificate is valid and signed by a cert that you trust. But in common scenarios, you know that the CN won't match the hostname you connected with. For those, set ServerName on tls.Config. If tls.Config.ServerName == remoteServerCN, then the certificate check will succeed. This is what you want. InsecureSkipVerify means that there is NO authentication; and it's ripe for a Man-In-The-Middle; defeating the purpose of using TLS.

There is one legitimate use for InsecureSkipVerify: use it to connect to a host and grab its certificate, then immediately disconnect. If you setup your code to use InsecureSkipVerify, it's generally because you didn't set ServerName properly (it will need to come from an env var or something - don't belly-ache about this requirement... do it correctly).

In particular, if you use client certs and rely on them for authentication, you basically have a fake login that doesn't actually login any more. Refuse code that does InsecureSkipVerify, or you will learn what is wrong with it the hard way!

"Could not run curl-config: [Errno 2] No such file or directory" when installing pycurl

I had this issue on Mac and it was related to the openssl package being an older version of what it was required by pycurl. pycurl can use other ssl libraries rather than openssl as per my understanding of it. Verify which ssl library you're using and update as it is very likely to fix the issue.

I fixed this by:

  • running brew upgrade
  • downloaded the latest pycurl-x.y.z.tar.gz from
  • extracted the package above and change directory into it
  • ran python --with-openssl install as openssl is the library I have installed. If you're ssl library is either gnutls or nss then will have to use --with-gnutls or --with-nss accordingly. You'll be able to find more installation info in their github repository.

AngularJS ng-click stopPropagation

In case that you're using a directive like me this is how it works when you need the two data way binding for example after updating an attribute in any model or collection:

angular.module('yourApp').directive('setSurveyInEditionMode', setSurveyInEditionMode)

function setSurveyInEditionMode() {
  return {
    restrict: 'A',
    link: function(scope, element, $attributes) {
      element.on('click', function(event){
        // In order to work with stopPropagation and two data way binding
        // if you don't use scope.$apply in my case the model is not updated in the view when I click on the element that has my directive
        scope.$apply(function () {
          scope.mySurvey.inEditionMode = true;
          console.log('inside the directive')

Now, you can easily use it in any button, link, div, etc. like so:

<button set-survey-in-edition-mode >Edit survey</button>

How to edit log message already committed in Subversion?

Essentially you have to have admin rights (directly or indirectly) to the repository to do this. You can either configure the repository to allow all users to do this, or you can modify the log message directly on the server.

See this part of the Subversion FAQ (emphasis mine):

Log messages are kept in the repository as properties attached to each revision. By default, the log message property (svn:log) cannot be edited once it is committed. That is because changes to revision properties (of which svn:log is one) cause the property's previous value to be permanently discarded, and Subversion tries to prevent you from doing this accidentally. However, there are a couple of ways to get Subversion to change a revision property.

The first way is for the repository administrator to enable revision property modifications. This is done by creating a hook called "pre-revprop-change" (see this section in the Subversion book for more details about how to do this). The "pre-revprop-change" hook has access to the old log message before it is changed, so it can preserve it in some way (for example, by sending an email). Once revision property modifications are enabled, you can change a revision's log message by passing the --revprop switch to svn propedit or svn propset, like either one of these:

$svn propedit -r N --revprop svn:log URL 
$svn propset -r N --revprop svn:log "new log message" URL 

where N is the revision number whose log message you wish to change, and URL is the location of the repository. If you run this command from within a working copy, you can leave off the URL.

The second way of changing a log message is to use svnadmin setlog. This must be done by referring to the repository's location on the filesystem. You cannot modify a remote repository using this command.

$ svnadmin setlog REPOS_PATH -r N FILE

where REPOS_PATH is the repository location, N is the revision number whose log message you wish to change, and FILE is a file containing the new log message. If the "pre-revprop-change" hook is not in place (or you want to bypass the hook script for some reason), you can also use the --bypass-hooks option. However, if you decide to use this option, be very careful. You may be bypassing such things as email notifications of the change, or backup systems that keep track of revision properties.

Visual Studio 2010 shortcut to find classes and methods?

Use the "Go To Find Combo Box" with the ">of" command. CTRL+/ or CTRL+D are the standard hotkeys.

For example, go to the combo box (CTRL+/) and type: >of MyClassName. As you type, intellisense will refine the options in the dropdown.

In my experience, this is faster than Navigate To and doesn't bring up another dialog to deal with. Also, this combo box has a lot of other nifty little shortcut commands:

Using the Go To Find Combo Box

This textbox used to be the default on the Standard toolbar in Visual Studio. It was removed in Visual Studio 2012, so you have to add it back using menu Tools ? Customize. The hotkeys may have changed too: I'm not sure since mine are all customized.

http://localhost/phpMyAdmin/ unable to connect

XAMPP by default uses http://localhost/phpmyadmin

It also requires you start both Apache and MySQL from the control panel (or as a service).

In the XAMPP Control Panel, clicking [ Admin ] on the MySQL line will open your default browser at the configured URL for the phpMyAdmin application.

If you get a phpMyAdmin error stating "Cannot connect: invalid settings." You will need to make sure your MySQL config file has a matching port for server and client. If it is not the standard 3306 port, you will also need to change your phpMyAdmin config file under apache ( to meet the new port settings. ( becomes<port>)

Best way to generate a random float in C#

Any reason not to use Random.NextDouble and then cast to float? That will give you a float between 0 and 1.

If you want a different form of "best" you'll need to specify your requirements. Note that Random shouldn't be used for sensitive matters such as finance or security - and you should generally reuse an existing instance throughout your application, or one per thread (as Random isn't thread-safe).

EDIT: As suggested in comments, to convert this to a range of float.MinValue, float.MaxValue:

// Perform arithmetic in double type to avoid overflowing
double range = (double) float.MaxValue - (double) float.MinValue;
double sample = rng.NextDouble();
double scaled = (sample * range) + float.MinValue;
float f = (float) scaled;

EDIT: Now you've mentioned that this is for unit testing, I'm not sure it's an ideal approach. You should probably test with concrete values instead - making sure you test with samples in each of the relevant categories - infinities, NaNs, denormal numbers, very large numbers, zero, etc.

How to re-create database for Entity Framework?

This worked for me:

  1. Delete database from SQL Server Object Explorer in Visual Studio. Right-click and select delete.
  2. Delete mdf and ldf files from file system - if they are still there.
  3. Rebuild Solution.
  4. Start Application - database will be re-created.

How to flatten only some dimensions of a numpy array

A slight generalization to Alexander's answer - np.reshape can take -1 as an argument, meaning "total array size divided by product of all other listed dimensions":

e.g. to flatten all but the last dimension:

>>> arr = numpy.zeros((50,100,25))
>>> new_arr = arr.reshape(-1, arr.shape[-1])
>>> new_arr.shape
# (5000, 25)

How to set div width using ng-style

ngStyle accepts a map:

$scope.myStyle = {
    "width" : "900px",
    "background" : "red"


Transfer data from one HTML file to another

The following is a sample code to pass values from one page to another using html. Here the data from page1 is passed to page2 and it's retrieved by using javascript.

1) page1.html

<!-- Value passing one page to another 
     Author: Codemaker
        <title> Page 1 - Codemaker</title>
        <form method="get" action="page2.html">
                    <td>First Name:</td>
                    <td><input type=text name=firstname size=10></td>
                    <td>Last Name:</td>
                    <td><input type=text name=lastname size=10></td>
                    <td><input type=text name=age size=10></td>
                    <td colspan=2><input type=submit value="Submit">

2) page2.html

<!-- Value passing one page to another 
     Author: Codemaker

        <title> Page 2 - Codemaker</title>
            function getParams(){
                var idx = document.URL.indexOf('?');
                var params = new Array();
                if (idx != -1) {
                    var pairs = document.URL.substring(idx+1, document.URL.length).split('&');
                    for (var i=0; i<pairs.length; i++){
                        nameVal = pairs[i].split('=');
                        params[nameVal[0]] = nameVal[1];
                return params;
            params = getParams();
            firstname = unescape(params["firstname"]);
            lastname = unescape(params["lastname"]);
            age = unescape(params["age"]);
            document.write("firstname = " + firstname + "<br>");
            document.write("lastname = " + lastname + "<br>");
            document.write("age = " + age + "<br>");

Unity 2d jumping script

Usually for jumping people use Rigidbody2D.AddForce with Forcemode.Impulse. It may seem like your object is pushed once in Y axis and it will fall down automatically due to gravity.


rigidbody2D.AddForce(new Vector2(0, 10), ForceMode2D.Impulse);

how to hide <li> bullets in navigation menu and footer links BUT show them for listing items

You can also define a class for the bullets you want to show, so in the CSS:

ul {list-style:none; list-style-type:none; list-style-image:none;}

And in the HTML you just define which lists to show:

<ul style="list-style:disc;">

Or you alternatively define a CSS class:

.show-list {list-style:disc;}

Then apply it to the list you want to show:

<ul class="show-list">

All other lists won't show the bullets...

Rotate image with javascript

You use a combination of CSS's transform (with vendor prefixes as necessary) and transform-origin, like this: (also on jsFiddle)

var angle = 0,_x000D_
  img = document.getElementById('container');_x000D_
document.getElementById('button').onclick = function() {_x000D_
  angle = (angle + 90) % 360;_x000D_
  img.className = "rotate" + angle;_x000D_
#container {_x000D_
  width: 820px;_x000D_
  height: 100px;_x000D_
  overflow: hidden;_x000D_
#container.rotate270 {_x000D_
  width: 100px;_x000D_
  height: 820px_x000D_
#image {_x000D_
  transform-origin: top left;_x000D_
  /* IE 10+, Firefox, etc. */_x000D_
  -webkit-transform-origin: top left;_x000D_
  /* Chrome */_x000D_
  -ms-transform-origin: top left;_x000D_
  /* IE 9 */_x000D_
#container.rotate90 #image {_x000D_
  transform: rotate(90deg) translateY(-100%);_x000D_
  -webkit-transform: rotate(90deg) translateY(-100%);_x000D_
  -ms-transform: rotate(90deg) translateY(-100%);_x000D_
#container.rotate180 #image {_x000D_
  transform: rotate(180deg) translate(-100%, -100%);_x000D_
  -webkit-transform: rotate(180deg) translate(-100%, -100%);_x000D_
  -ms-transform: rotate(180deg) translateX(-100%, -100%);_x000D_
#container.rotate270 #image {_x000D_
  transform: rotate(270deg) translateX(-100%);_x000D_
  -webkit-transform: rotate(270deg) translateX(-100%);_x000D_
  -ms-transform: rotate(270deg) translateX(-100%);_x000D_
<button id="button">Click me!</button>_x000D_
<div id="container">_x000D_
  <img src="" id="image" />_x000D_

CS0120: An object reference is required for the nonstatic field, method, or property 'foo'

It looks like you are calling a non static member (a property or method, specifically setTextboxText) from a static method (specifically SumData). You will need to either:

  1. Make the called member static also:

    static void setTextboxText(int result)
        // Write static logic for setTextboxText.  
        // This may require a static singleton instance of Form1.
  2. Create an instance of Form1 within the calling method:

    private static void SumData(object state)
        int result = 0;
        //int[] icount = (int[])state;
        int icount = (int)state;
        for (int i = icount; i > 0; i--)
            result += i;
        Form1 frm1 = new Form1();

    Passing in an instance of Form1 would be an option also.

  3. Make the calling method a non-static instance method (of Form1):

    private void SumData(object state)
        int result = 0;
        //int[] icount = (int[])state;
        int icount = (int)state;
        for (int i = icount; i > 0; i--)
            result += i;

More info about this error can be found on MSDN.

How to install VS2015 Community Edition offline

You can download the ISO from (even if it has "beta" in the URL you'll have the latest stable version. Currently update 3)

VS2015 Community download

Add vertical whitespace using Twitter Bootstrap?

I merely created a div class using various heights i.e.

<div class="divider-10"></div>

The CSS is:

.divider-10 {

Just create a divider class for what ever heights are needed.

Understanding ASP.NET Eval() and Bind()

For read-only controls they are the same. For 2 way databinding, using a datasource in which you want to update, insert, etc with declarative databinding, you'll need to use Bind.

Imagine for example a GridView with a ItemTemplate and EditItemTemplate. If you use Bind or Eval in the ItemTemplate, there will be no difference. If you use Eval in the EditItemTemplate, the value will not be able to be passed to the Update method of the DataSource that the grid is bound to.

UPDATE: I've come up with this example:

<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">

<html xmlns="">
<head runat="server">
    <title>Data binding demo</title>
    <form id="form1" runat="server">
                        <%# Eval("Name") %>
                            Text='<%# Bind("Name") %>' 

        TypeName="MyCompany.CustomDataSource" />

And here's the definition of a custom class that serves as object data source:

public class CustomDataSource
    public class Model
        public string Name { get; set; }

    public IEnumerable<Model> Select()
        return new[] 
            new Model { Name = "some value" }

    public void Update(string Name)
        // This method will be called if you used Bind for the TextBox
        // and you will be able to get the new name and update the
        // data source accordingly

    public void Update()
        // This method will be called if you used Eval for the TextBox
        // and you will not be able to get the new name that the user
        // entered

How to convert CSV file to multiline JSON?

The problem with your desired output is that it is not valid json document,; it's a stream of json documents!

That's okay, if its what you need, but that means that for each document you want in your output, you'll have to call json.dumps.

Since the newline you want separating your documents is not contained in those documents, you're on the hook for supplying it yourself. So we just need to pull the loop out of the call to json.dump and interpose newlines for each document written.

import csv
import json

csvfile = open('file.csv', 'r')
jsonfile = open('file.json', 'w')

fieldnames = ("FirstName","LastName","IDNumber","Message")
reader = csv.DictReader( csvfile, fieldnames)
for row in reader:
    json.dump(row, jsonfile)

Generate a random number in the range 1 - 10

Actually I don't know you want to this.

try this

INSERT INTO my_table (my_column)
    (random() * 10) + 1

Align DIV's to bottom or baseline

An old post but thought i would share an answer for anyone looking. And because when you use absolute things can go wrong. What I would do is


<div id="parentDiv"></div>
<div class="childDiv"></div>

The Css



And that would just sit that bottom div back up into the parent div. safe for most browsers too

Which is faster: Stack allocation or Heap allocation

Usually stack allocation just consists of subtracting from the stack pointer register. This is tons faster than searching a heap.

Sometimes stack allocation requires adding a page(s) of virtual memory. Adding a new page of zeroed memory doesn't require reading a page from disk, so usually this is still going to be tons faster than searching a heap (especially if part of the heap was paged out too). In a rare situation, and you could construct such an example, enough space just happens to be available in part of the heap which is already in RAM, but allocating a new page for the stack has to wait for some other page to get written out to disk. In that rare situation, the heap is faster.

How to rename a file using Python

#src and dst should be inside Folder2

Exception: "URI formats are not supported"

     string ImagePath = "";

        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(ImagePath);
        string a = "";
            HttpWebResponse response = (HttpWebResponse)request.GetResponse(); 
            Stream receiveStream = response.GetResponseStream();
            if (receiveStream.CanRead)
            { a = "OK"; }

        catch { }

File Upload to HTTP server in iphone programming

ASIHTTPRequest is a great wrapper around the network APIs and makes it very easy to upload a file. Here's their example (but you can do this on the iPhone too - we save images to "disk" and later upload them.

ASIFormDataRequest *request = [[[ASIFormDataRequest alloc] initWithURL:url] autorelease];
[request setPostValue:@"Ben" forKey:@"first_name"];
[request setPostValue:@"Copsey" forKey:@"last_name"];
[request setFile:@"/Users/ben/Desktop/ben.jpg" forKey:@"photo"];

Python main call within class

Well, first, you need to actually define a function before you can run it (and it doesn't need to be called main). For instance:

class Example(object):
    def run(self):
        print "Hello, world!"

if __name__ == '__main__':

You don't need to use a class, though - if all you want to do is run some code, just put it inside a function and call the function, or just put it in the if block:

def main():
    print "Hello, world!"

if __name__ == '__main__':


if __name__ == '__main__':
    print "Hello, world!"

Hide/Show Action Bar Option Menu Item for different fragments

This is one way of doing this:

add a "group" to your menu:

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="" >

         <item android:id="@+id/done_item"

then, add a

Menu menu;

variable to your activity and set it in your override of onCreateOptionsMenu:

public boolean onCreateOptionsMenu(Menu menu) { = menu;
    // inflate your menu here

After, add and use this function to your activity when you'd like to show/hide the menu:

public void showOverflowMenu(boolean showMenu){
    if(menu == null)
    menu.setGroupVisible(, showMenu);

I am not saying this is the best/only way, but it works well for me.

cmake - find_library - custom library location

The simplest solution may be to add HINTS to each find_* request.

For example:

    NAMES curl curllib libcurl_imp curllib_static
    HINTS "${CMAKE_PREFIX_PATH}/curl/lib"

For Boost I would strongly recommend using the FindBoost standard module and setting the BOOST_DIR variable to point to your Boost libraries.

Grab a segment of an array in Java without creating a new array on heap

One way is to wrap the array in java.nio.ByteBuffer, use the absolute put/get functions, and slice the buffer to work on a subarray.

For instance:

doSomething(ByteBuffer twoBytes) {
    byte b1 = twoBytes.get(0);
    byte b2 = twoBytes.get(1);

void someMethod(byte[] bigArray) {
      int offset = 4;
      int length = 2;
      doSomething(ByteBuffer.wrap(bigArray, offset, length).slice());

Note that you have to call both wrap() and slice(), since wrap() by itself only affects the relative put/get functions, not the absolute ones.

ByteBuffer can be a bit tricky to understand, but is most likely efficiently implemented, and well worth learning.

When is the finalize() method called in Java?

In general it's best not to rely on finalize() to do any cleaning up etc.

According to the Javadoc (which it would be worth reading), it is:

Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.

As Joachim pointed out, this may never happen in the life of a program if the object is always accessible.

Also, the garbage collector is not guaranteed to run at any specific time. In general, what I'm trying to say is finalize() is probably not the best method to use in general unless there's something specific you need it for.

R numbers from 1 to 100

If you need the construct for a quick example to play with, use the : operator.

But if you are creating a vector/range of numbers dynamically, then use seq() instead.

Let's say you are creating the vector/range of numbers from a to b with a:b, and you expect it to be an increasing series. Then, if b is evaluated to be less than a, you will get a decreasing sequence but you will never be notified about it, and your program will continue to execute with the wrong kind of input.

In this case, if you use seq(), you can set the sign of the by argument to match the direction of your sequence, and an error will be raised if they do not match. For example,

seq(a, b, -1)

will raise an error for a=2, b=6, because the coder expected a decreasing sequence.

How can I make a weak protocol reference in 'pure' Swift (without @objc)

protocol must be subClass of AnyObject, class

example given below

    protocol NameOfProtocol: class {
   // member of protocol
   class ClassName: UIViewController {
      weak var delegate: NameOfProtocol? 

How can I get the name of an object in Python?

Generally when you are wanting to do something like this, you create a class to hold all of these functions and name them with some clear prefix cmd_ or the like. You then take the string from the command, and try to get that attribute from the class with the cmd_ prefixed to it. Now you only need to add a new function/method to the class, and it's available to your callers. And you can use the doc strings for automatically creating the help text.

As described in other answers, you may be able to do the same approach with globals() and regular functions in your module to more closely match what you asked for.

Something like this:

class Tasks:
    def cmd_doit(self):
        # do it here

func_name = parse_commandline()
    func = getattr('cmd_' + func_name, Tasks())
except AttributeError:
    # bad command: exit or whatever

How to create custom config section in app.config?

Import namespace :

using System.Configuration;

Create ConfigurationElement Company :

public class Company : ConfigurationElement

        [ConfigurationProperty("name", IsRequired = true)]
        public string Name
                return this["name"] as string;
            [ConfigurationProperty("code", IsRequired = true)]
        public string Code
                return this["code"] as string;


public class Companies
        : ConfigurationElementCollection
        public Company this[int index]
                return base.BaseGet(index) as Company ;
                if (base.BaseGet(index) != null)
                this.BaseAdd(index, value);

       public new Company this[string responseString]
            get { return (Company) BaseGet(responseString); }
                if(BaseGet(responseString) != null)

        protected override System.Configuration.ConfigurationElement CreateNewElement()
            return new Company();

        protected override object GetElementKey(System.Configuration.ConfigurationElement element)
            return ((Company)element).Name;

and ConfigurationSection:

public class RegisterCompaniesConfig
        : ConfigurationSection

        public static RegisterCompaniesConfig GetConfig()
            return (RegisterCompaniesConfig)System.Configuration.ConfigurationManager.GetSection("RegisterCompanies") ?? new RegisterCompaniesConfig();

            [ConfigurationCollection(typeof(Companies), AddItemName = "Company")]
        public Companies Companies
                object o = this["Companies"];
                return o as Companies ;


and you must also register your new configuration section in web.config (app.config):

          <section name="Companies" type="blablabla.RegisterCompaniesConfig" ..>

then you load your config with

var config = RegisterCompaniesConfig.GetConfig();
foreach(var item in config.Companies)
   do something ..

How to convert byte array to string

Assuming that you are using UTF-8 encoding:

string convert = "This is the string to be converted";

// From string to byte array
byte[] buffer = System.Text.Encoding.UTF8.GetBytes(convert);

// From byte array to string
string s = System.Text.Encoding.UTF8.GetString(buffer, 0, buffer.Length);

How to drop all tables in a SQL Server database?

For Temporal Tables it is a bit more complicated due to the fact there may be some foreign keys and also exception:

Drop table operation failed on table XXX because it is not a supported operation on system-versioned temporal tables

What you can use is:

-- Disable constraints (foreign keys)

-- Disable system versioning (temporial tables)
EXEC sp_MSForEachTable '
 IF OBJECTPROPERTY(object_id(''?''), ''TableTemporalType'') = 2

-- Removing tables
EXEC sp_MSForEachTable 'DROP TABLE ?'

Fastest way to flatten / un-flatten nested JSON objects

You can use

Take a nested Javascript object and flatten it, or unflatten an object with delimited keys.

Example from the doc

var flatten = require('flat')

    key1: {
        keyA: 'valueI'
    key2: {
        keyB: 'valueII'
    key3: { a: { b: { c: 2 } } }

// {
//   'key1.keyA': 'valueI',
//   'key2.keyB': 'valueII',
//   'key3.a.b.c': 2
// }

var unflatten = require('flat').unflatten

    'three.levels.deep': 42,
    'three.levels': {
        nested: true

// {
//     three: {
//         levels: {
//             deep: 42,
//             nested: true
//         }
//     }
// }

How do I give text or an image a transparent background using CSS?

In Firefox 3 and Safari 3, you can use RGBA like Georg Schölly mentioned.

A little known trick is that you can use it in Internet Explorer as well using the gradient filter.

background-color: rgba(0, 255, 0, 0.5);
filter: progid:DXImageTransform.Microsoft.Gradient(GradientType=0, StartColorStr='#7F00FF00', EndColorStr='#7F00FF00');

The first hex number defines the alpha value of the color.

Full solution all browsers:

.alpha60 {
    /* Fallback for web browsers that doesn't support RGBa */
    background: rgb(0, 0, 0) transparent;
    /* RGBa with 0.6 opacity */
    background: rgba(0, 0, 0, 0.6);
    /* For IE 5.5 - 7*/
    filter:progid:DXImageTransform.Microsoft.gradient(startColorstr=#99000000, endColorstr=#99000000);
    /* For IE 8*/
    -ms-filter: "progid:DXImageTransform.Microsoft.gradient(startColorstr=#99000000, endColorstr=#99000000)";

This is from CSS background transparency without affecting child elements, through RGBa and filters.

Screenshots proof of results:

This is when using the following code:

     <meta http-equiv="X-UA-Compatible" content="IE=edge" >
    <title>An XHTML 1.0 Strict standard template</title>
     <meta http-equiv="content-type" content="text/html;charset=utf-8" />
    <style type="text/css" media="all">
         .transparent-background-with-text-and-images-on-top {
             background: rgb(0, 0, 0) transparent;   /* Fallback for web browsers that doesn't support RGBa */
            background: rgba(0, 0, 0, 0.6);   /* RGBa with 0.6 opacity */
             filter:progid:DXImageTransform.Microsoft.gradient(startColorstr=#99000000, endColorstr=#99000000);  /* For IE 5.5 - 7*/
            -ms-filter: "progid:DXImageTransform.Microsoft.gradient(startColorstr=#99000000, endColorstr=#99000000)";  /* For IE 8*/

     <div class="transparent-background-with-text-and-images-on-top">
         <p>Here some content (text AND images) "on top of the transparent background"</p>
        <img src="">

Chrome-33 IE11 IE9 IE8

Controlling Maven final name of jar artifact

This works for me

mvn jar:jar -Djar.finalName=custom-jar-name

Detect element content changes with jQuery

You can add a callback option to html (,or any) function:

$.fn.oldHtml = $.fn.html;
$.fn.html = function(html,fn){
  fn = fn || function(){};
  var result =  this.oldHtml(html);
  return result;

Demo here.

You do the change on some element, not the element is forced to change by something that you have to catch.

Select SQL Server database size

Also compare the results with the following query's result

EXEC sp_helpdb @dbname= 'MSDB'

It produces result similar to the following

enter image description here

There is a good article - Different ways to determine free space for SQL Server databases and database files

Git push/clone to new server

  1. git remote add name url
  2. git push name branch


git remote add origin [email protected]:foo/bar.git
git push origin master

See the docs for git push -- you can set a remote as the default remote for a given branch; if you don't, the name origin is special. Just git push alone will do the same as git push origin thisbranch (for whatever branch you're on).

I want to exception handle 'list index out of range.'

Handling the exception is the way to go:

    gotdata = dlist[1]
except IndexError:
    gotdata = 'null'

Of course you could also check the len() of dlist; but handling the exception is more intuitive.

Why I can't change directories using "cd"?

This combines the answer by Serge with an unrelated answer by David. It changes the directory, and then instead of forcing a bash shell, it launches the user's default shell. It however requires both getent and /etc/passwd to detect the default shell.

#!/usr/bin/env bash
cd desired/directory
USER_SHELL=$(getent passwd <USER> | cut -d : -f 7)

Of course this still has the same deficiency of creating a nested shell.

How to obfuscate Python code effectively?

I would mask the code like this:

def MakeSC():
    c = raw_input(" Encode: ")
    sc = "\\x" + "\\x".join("{0:x}".format(ord(c)) for c in c)
    print "\n shellcode =('" + sc + "'); exec(shellcode)"; MakeSC();


import os; os.system("whoami")


Payload = ('\x69\x6d\x70\x6f\x72\x74\x20\x6f\x73\x3b\x20\x6f\x73\x2e\x73\x79\x73\x74\x65\x6d\x28\x22\x77\x68\x6f\x61\x6d\x69\x22\x29'); exec(Payload);

Get height of div with no height set in css

Also make sure the div is currently appended to the DOM and visible.

c++ string array initialization

Prior to C++11, you cannot initialise an array using type[]. However the latest c++11 provides(unifies) the initialisation, so you can do it in this way:

string* pStr = new string[3] { "hi", "there"};


Max length UITextField

You need to check whether the existing string plus the input is greater than 10.

   func textField(textField: UITextField!,shouldChangeCharactersInRange range: NSRange,    replacementString string: String!) -> Bool {
      NSUInteger newLength = textField.text.length + string.length - range.length;
      return !(newLength > 10)

Insert, on duplicate update in PostgreSQL?

I use this function merge

    IF EXISTS(SELECT a FROM tabla WHERE a = key)
            UPDATE tabla SET b = data WHERE a = key;
        INSERT INTO tabla(a,b) VALUES (key, data);
    END IF;
LANGUAGE plpgsql

PHP check whether property exists in object or class

To check if the property exists and if it's null too, you can use the function property_exists().


As opposed with isset(), property_exists() returns TRUE even if the property has the value NULL.

bool property_exists ( mixed $class , string $property )


if (property_exists($testObject, $property)) {
    //do something

Change values of select box of "show 10 entries" of jquery datatable

$(document).ready(function() {
    $('#example').dataTable( {
    "aLengthMenu": [[25, 50, 75, -1], [25, 50, 75, "All"]],
    "pageLength": 25
    } );
} );

aLengthMenu : This parameter allows you to readily specify the entries in the length drop down menu that DataTables shows when pagination is enabled. It can be either a 1D array of options which will be used for both the displayed option and the value, or a 2D array which will use the array in the first position as the value, and the array in the second position as the displayed options (useful for language strings such as 'All').


Since DataTables v1.10, the options you are looking for are pageLength and lengthMenu

Define global constants

The best way to create application wide constants in Angular 2 is by using environment.ts files. The advantage of declaring such constants is that you can vary them according to the environment as there can be a different environment file for each environment.

KERNELBASE.dll Exception 0xe0434352 offset 0x000000000000a49d

0xe0434352 is the SEH code for a CLR exception. If you don't understand what that means, stop and read A Crash Course on the Depths of Win32™ Structured Exception Handling. So your process is not handling a CLR exception. Don't shoot the messenger, KERNELBASE.DLL is just the unfortunate victim. The perpetrator is MyApp.exe.

There should be a minidump of the crash in DrWatson folders with a full stack, it will contain everything you need to root cause the issue.

I suggest you wire up, in your myapp.exe code, AppDomain.UnhandledException and Application.ThreadException, as appropriate.

Center Triangle at Bottom of Div

You can use following css to make an element middle aligned styled with position: absolute:

.element {
  transform: translateX(-50%);
  position: absolute;
  left: 50%;

With CSS having only left: 50% we will have following effect:

Image with left: 50% property only

While combining left: 50% with transform: translate(-50%) we will have following:

Image with transform: translate(-50%) as well

.hero {  _x000D_
  background-color: #e15915;_x000D_
  position: relative;_x000D_
  height: 320px;_x000D_
  width: 100%;_x000D_
.hero:after {_x000D_
  border-right: solid 50px transparent;_x000D_
  border-left: solid 50px transparent;_x000D_
  border-top: solid 50px #e15915;_x000D_
  transform: translateX(-50%);_x000D_
  position: absolute;_x000D_
  z-index: -1;_x000D_
  content: '';_x000D_
  top: 100%;_x000D_
  left: 50%;_x000D_
  height: 0;_x000D_
  width: 0;_x000D_
<div class="hero">_x000D_

GROUP BY and COUNT in PostgreSQL

There is also EXISTS:

SELECT count(*) AS post_ct
FROM   posts p
WHERE  EXISTS (SELECT FROM votes v WHERE v.post_id =;

In Postgres and with multiple entries on the n-side like you probably have, it's generally faster than count(DISTINCT post_id):

SELECT count(DISTINCT AS post_ct
FROM   posts p
JOIN   votes v ON v.post_id =;

The more rows per post there are in votes, the bigger the difference in performance. Test with EXPLAIN ANALYZE.

count(DISTINCT post_id) has to read all rows, sort or hash them, and then only consider the first per identical set. EXISTS will only scan votes (or, preferably, an index on post_id) until the first match is found.

If every post_id in votes is guaranteed to be present in the table posts (referential integrity enforced with a foreign key constraint), this short form is equivalent to the longer form:

SELECT count(DISTINCT post_id) AS post_ct
FROM   votes;

May actually be faster than the EXISTS query with no or few entries per post.

The query you had works in simpler form, too:

SELECT count(*) AS post_ct
    SELECT FROM posts 
    JOIN   votes ON votes.post_id = 
    ) sub;


To verify my claims I ran a benchmark on my test server with limited resources. All in a separate schema:

Test setup

Fake a typical post / vote situation:

SET search_path = y;

  id   int PRIMARY KEY
, post text

SELECT g, repeat(chr(g%100 + 32), (random()* 500)::int)  -- random text
FROM   generate_series(1,10000) g;

DELETE FROM posts WHERE random() > 0.9;  -- create ~ 10 % dead tuples

  vote_id serial PRIMARY KEY
, post_id int REFERENCES posts(id)
, up_down bool

INSERT INTO votes (post_id, up_down)
   SELECT ((random()* 21)^3)::int + 1111 AS post_id  -- uneven distribution
        , random()::int::bool AS up_down
   FROM   generate_series(1,70000)
   ) g
JOIN   posts p ON = g.post_id;

All of the following queries returned the same result (8093 of 9107 posts had votes).
I ran 4 tests with EXPLAIN ANALYZE ant took the best of five on Postgres 9.1.4 with each of the three queries and appended the resulting total runtimes.

  1. As is.

  2. After ..

    ANALYZE posts;
    ANALYZE votes;
  3. After ..

    CREATE INDEX foo on votes(post_id);
  4. After ..

    CLUSTER votes using foo;

count(*) ... WHERE EXISTS

  1. 253 ms
  2. 220 ms
  3. 85 ms -- winner (seq scan on posts, index scan on votes, nested loop)
  4. 85 ms

count(DISTINCT x) - long form with join

  1. 354 ms
  2. 358 ms
  3. 373 ms -- (index scan on posts, index scan on votes, merge join)
  4. 330 ms

count(DISTINCT x) - short form without join

  1. 164 ms
  2. 164 ms
  3. 164 ms -- (always seq scan)
  4. 142 ms

Best time for original query in question:

  • 353 ms

For simplified version:

  • 348 ms

@wildplasser's query with a CTE uses the same plan as the long form (index scan on posts, index scan on votes, merge join) plus a little overhead for the CTE. Best time:

  • 366 ms

Index-only scans in the upcoming PostgreSQL 9.2 can improve the result for each of these queries, most of all for EXISTS.

Related, more detailed benchmark for Postgres 9.5 (actually retrieving distinct rows, not just counting):

Word-wrap in an HTML table

The answer that won the bounty is correct, but it doesn't work if the first row of the table has a merged/joined cell (all the cells get equal width).

In this case you should use the colgroup and col tags to display it properly:

<table style="table-layout: fixed; width: 200px">
    <col style="width: 30%;">
    <col style="width: 70%;">
    <td colspan="2">Merged cell</td>
    <td style="word-wrap: break-word">VeryLongWordInThisCell</td>
    <td style="word-wrap: break-word">Cell 2</td>

How do I make a transparent canvas in html5?

Canvases are transparent by default.

Try setting a page background image, and then put a canvas over it. If nothing is drawn on the canvas, you can fully see the page background.

Think of a canvas as like painting on a glass plate.

A component is changing an uncontrolled input of type text to be controlled error in ReactJS

Changing value to defaultValue will resolve it.


defaultValue is only for the initial load. If you want to initialize the input then you should use defaultValue, but if you want to use state to change the value then you need to use value. Read this for more.

I used value={this.state.input ||""} in input to get rid of that warning.

Code coverage with Mocha

You need an additional library for code coverage, and you are going to be blown away by how powerful and easy istanbul is. Try the following, after you get your mocha tests to pass:

npm install nyc

Now, simply place the command nyc in front of your existing test command, for example:

  "scripts": {
    "test": "nyc mocha"

Java: Difference between the setPreferredSize() and setSize() methods in components

Usage depends on whether the component's parent has a layout manager or not.

  • setSize() -- use when a parent layout manager does not exist;
  • setPreferredSize() (also its related setMinimumSize and setMaximumSize) -- use when a parent layout manager exists.

The setSize() method probably won't do anything if the component's parent is using a layout manager; the places this will typically have an effect would be on top-level components (JFrames and JWindows) and things that are inside of scrolled panes. You also must call setSize() if you've got components inside a parent without a layout manager.

Generally, setPreferredSize() will lay out the components as expected if a layout manager is present; most layout managers work by getting the preferred (as well as minimum and maximum) sizes of their components, then using setSize() and setLocation() to position those components according to the layout's rules.

For example, a BorderLayout tries to make the bounds of its "north" region equal to the preferred size of its north component---they may end up larger or smaller than that, depending on the size of the JFrame, the size of the other components in the layout, and so on.

regular expression for Indian mobile numbers


Is also a valid expression. You can precede it with either 0091,+91 or 0 and is optional.

For more details with code sample, refer to my blog.

DB2 SQL error: SQLCODE: -206, SQLSTATE: 42703

That only means that an undefined column or parameter name was detected. The errror that DB2 gives should point what that may be:


Double check your table definition. Maybe you just missed adding something.

I also tried google-ing this problem and saw this:

How to delete/remove nodes on Firebase

As others have noted the call to .remove() is asynchronous. We should all be aware nothing happens 'instantly', even if it is at the speed of light.

What you mean by 'instantly' is that the next line of code should be able to execute after the call to .remove(). With asynchronous operations the next line may be when the data has been removed, it may not - it is totally down to chance and the amount of time that has elapsed.

.remove() takes one parameter a callback function to help deal with this situation to perform operations after we know that the operation has been completed (with or without an error). .push() takes two params, a value and a callback just like .remove().

Here is your example code with modifications:

ref = new Firebase("")

ref.push({key:val}, function(error){
  //do stuff after push completed

// deletes all data pushed so far
  //do stuff after removal

What is the difference between exit and return?

  • return returns from the current function; it's a language keyword like for or break.
  • exit() terminates the whole program, wherever you call it from. (After flushing stdio buffers and so on).

The only case when both do (nearly) the same thing is in the main() function, as a return from main performs an exit().

In most C implementations, main is a real function called by some startup code that does something like int ret = main(argc, argv); exit(ret);. The C standard guarantees that something equivalent to this happens if main returns, however the implementation handles it.

Example with return:

#include <stdio.h>

void f(){
    printf("Executing f\n");

int main(){
    printf("Back from f\n");

If you execute this program it prints:

Executing f
Back from f

Another example for exit():

#include <stdio.h>
#include <stdlib.h>

void f(){
    printf("Executing f\n");

int main(){
    printf("Back from f\n");

If you execute this program it prints:

Executing f

You never get "Back from f". Also notice the #include <stdlib.h> necessary to call the library function exit().

Also notice that the parameter of exit() is an integer (it's the return status of the process that the launcher process can get; the conventional usage is 0 for success or any other value for an error).

The parameter of the return statement is whatever the return type of the function is. If the function returns void, you can omit the return at the end of the function.

Last point, exit() come in two flavors _exit() and exit(). The difference between the forms is that exit() (and return from main) calls functions registered using atexit() or on_exit() before really terminating the process while _exit() (from #include <unistd.h>, or its synonymous _Exit from #include <stdlib.h>) terminates the process immediately.

Now there are also issues that are specific to C++.

C++ performs much more work than C when it is exiting from functions (return-ing). Specifically it calls destructors of local objects going out of scope. In most cases programmers won't care much of the state of a program after the processus stopped, hence it wouldn't make much difference: allocated memory will be freed, file ressource closed and so on. But it may matter if your destructor performs IOs. For instance automatic C++ OStream locally created won't be flushed on a call to exit and you may lose some unflushed data (on the other hand static OStream will be flushed).

This won't happen if you are using the good old C FILE* streams. These will be flushed on exit(). Actually, the rule is the same that for registered exit functions, FILE* will be flushed on all normal terminations, which includes exit(), but not calls to _exit() or abort().

You should also keep in mind that C++ provide a third way to get out of a function: throwing an exception. This way of going out of a function will call destructor. If it is not catched anywhere in the chain of callers, the exception can go up to the main() function and terminate the process.

Destructors of static C++ objects (globals) will be called if you call either return from main() or exit() anywhere in your program. They wont be called if the program is terminated using _exit() or abort(). abort() is mostly useful in debug mode with the purpose to immediately stop the program and get a stack trace (for post mortem analysis). It is usually hidden behind the assert() macro only active in debug mode.

When is exit() useful ?

exit() means you want to immediately stops the current process. It can be of some use for error management when we encounter some kind of irrecoverable issue that won't allow for your code to do anything useful anymore. It is often handy when the control flow is complicated and error codes has to be propagated all way up. But be aware that this is bad coding practice. Silently ending the process is in most case the worse behavior and actual error management should be preferred (or in C++ using exceptions).

Direct calls to exit() are especially bad if done in libraries as it will doom the library user and it should be a library user's choice to implement some kind of error recovery or not. If you want an example of why calling exit() from a library is bad, it leads for instance people to ask this question.

There is an undisputed legitimate use of exit() as the way to end a child process started by fork() on Operating Systems supporting it. Going back to the code before fork() is usually a bad idea. This is the rationale explaining why functions of the exec() family will never return to the caller.

ERROR Source option 1.5 is no longer supported. Use 1.6 or later

You need to set JDK 1.5 to your project and also all dependent project or jar file should also compiled with JDK 1.5

Getting text from td cells with jQuery

You can use .map:

// array of text of each td

var texts = $("td").map(function() {
    return $(this).text();

How to set background image in Java?

Or try this ;)

try {
    new JLabel(new ImageIcon( File("your_file.jpeg")))));
} catch (IOException e) {};

Convert Python ElementTree to string

How do I convert ElementTree.Element to a String?

For Python 3:

xml_str = ElementTree.tostring(xml, encoding='unicode')

For Python 2:

xml_str = ElementTree.tostring(xml, encoding='utf-8')

The following is compatible with both Python 2 & 3, but only works for Latin characters:

xml_str = ElementTree.tostring(xml).decode()

Example usage

from xml.etree import ElementTree

xml = ElementTree.Element("Person", Name="John")
xml_str = ElementTree.tostring(xml).decode()


<Person Name="John" />


Despite what the name implies, ElementTree.tostring() returns a bytestring by default in Python 2 & 3. This is an issue in Python 3, which uses Unicode for strings.

In Python 2 you could use the str type for both text and binary data. Unfortunately this confluence of two different concepts could lead to brittle code which sometimes worked for either kind of data, sometimes not. [...]

To make the distinction between text and binary data clearer and more pronounced, [Python 3] made text and binary data distinct types that cannot blindly be mixed together.

Source: Porting Python 2 Code to Python 3

If we know what version of Python is being used, we can specify the encoding as unicode or utf-8. Otherwise, if we need compatibility with both Python 2 & 3, we can use decode() to convert into the correct type.

For reference, I've included a comparison of .tostring() results between Python 2 and Python 3.

# Python 3: b'<Person Name="John" />'
# Python 2: <Person Name="John" />

ElementTree.tostring(xml, encoding='unicode')
# Python 3: <Person Name="John" />
# Python 2: LookupError: unknown encoding: unicode

ElementTree.tostring(xml, encoding='utf-8')
# Python 3: b'<Person Name="John" />'
# Python 2: <Person Name="John" />

# Python 3: <Person Name="John" />
# Python 2: <Person Name="John" />

Thanks to Martijn Peters for pointing out that the str datatype changed between Python 2 and 3.

Why not use str()?

In most scenarios, using str() would be the "cannonical" way to convert an object to a string. Unfortunately, using this with Element returns the object's location in memory as a hexstring, rather than a string representation of the object's data.

from xml.etree import ElementTree

xml = ElementTree.Element("Person", Name="John")
print(str(xml))  # <Element 'Person' at 0x00497A80>

What is the difference between an IntentService and a Service?

Intent service is child of Service

IntentService: If you want to download a bunch of images at the start of opening your app. It's a one-time process and can clean itself up once everything is downloaded.

Service: A Service which will constantly be used to communicate between your app and back-end with web API calls. Even if it is finished with its current task, you still want it to be around a few minutes later, for more communication

Order a MySQL table by two columns

Default sorting is ascending, you need to add the keyword DESC to both your orders:

ORDER BY article_rating DESC, article_time DESC

How to compare timestamp dates with date-only parameter in MySQL?

As suggested by some, by using DATE(timestamp) you are applying manipulation to the column and therefore you cannot rely on the index ordering.

However, using BETWEEN would only be reliable if you include the milliseconds. In the example timestamp BETWEEN '2012-05-05 00:00:00' AND '2012-05-05 23:59:59' you exclude records with a timestamp between 2012-05-05 23:59:59.001 and 2012-05-05 23:59:59.999. However, even this method has some problems, because of the datatypes precision. Occasionally 999 milliseconds is rounded up.

The best thing to do is:

WHERE date>='2012-05-05' AND date<'2012-05-06'

Sublime Text 2 - View whitespace characters

If you really only want to see trailing spaces, this ST2 plugin will do the trick:

Check if string contains only letters in javascript

You need


Currently, you are matching a single character at the start of the input. If your goal is to match letter characters (one or more) from start to finish, then you need to repeat the a-z character match (using +) and specify that you want to match all the way to the end (via $)

Why would an Enum implement an Interface?

It's required for extensibility -- if someone uses an API you've developed, the enums you define are static; they can't be added to or modified. However, if you let it implement an interface, the person using the API can develop their own enum using the same interface. You can then register this enum with an enum manager which conglomerates the enums together with the standard interface.

Edit: @Helper Method has the perfect example of this. Think about having other libraries defining new operators and then telling a manager class that 'hey, this enum exists -- register it'. Otherwise, you'd only be able to define Operators in your own code - there'd be no extensibility.

index.php not loading by default

This post might be old but i am just posting it incase it helps some other person, I would not advise to Create a .htaccess file in your web root and change the index. I feel it is better to follow the steps

  1. Go to the conf folder of your apache folder mine is


  2. Open the file named


  3. Go to the section

    <IfModule dir_module>
       DirectoryIndex index.html 
  4. Add index.php to it as shown below

     <IfModule dir_module>
      DirectoryIndex index.html index.php

This way, it still picks index.html and index.php as the default index but giving priority to index.html because index.html came before *index.php. By this I mean in you have both index.html and index.php in the same directory, the index.html will be used as the default index except you write **index.php* before index.hml

I hope it helps someone... Happy Coding

How to initialize a struct in accordance with C programming language standards

a = (MYTYPE){ true, 15, 0.123 };

would do fine in C99

Android Google Maps v2 - set zoom level for myLocation

You can also use:

mMap.animateCamera( CameraUpdateFactory.zoomTo( 17.0f ) );    

To just change the zoom value to any desired value between minimum value=2.0 and maximum value=21.0.

The API warns that not all locations have tiles at values at or near maximum zoom.

See this for more information about zoom methods available in the CameraUpdateFactory.

How to switch to new window in Selenium for Python?

We can handle the different windows by moving between named windows using the “switchTo” method:


<a href="somewhere.html" target="windowName">Click here to open a new window</a>

Alternatively, you can pass a “window handle” to the “switchTo().window()” method. Knowing this, it’s possible to iterate over every open window like so:

for handle in driver.window_handles:

How can I have Github on my own server?

I searched for git PHP implementations too, but with no results. The only way to re-create a site similar to GitHub is to setup a "real" git server on your own server and then use a PHP git web client like

Unfortunatly, you can forget to do this with a hosting solution. You need a real virtual server where you can install everything you want.

However, if you need a place where store some personal, non-public, non-accessible-to-everyone code for a project, you can try BitBucket. It offers private and private-shared git repos for free.

How do I revert all local changes in Git managed project to previous state?

This question is more about broader repository reset / revert, but in case if you're interested in reverting individual change - I've added similar answer in here:

Answers to questions:

  • How to revert individual change with or without change preserving in git history

  • How to return back to old version to restart from same state

How to open Android Device Monitor in latest Android Studio 3.1

Android Device Monitor was deprecated in Android Studio 3.1 and removed from Android Studio 3.2

Use Android Profiler introduced in Android Studio 3.0 to measure the cpu utilisation, network, memory etc,. To open Android Profiler: View -> Tool Windows -> Profiler.

Android Device Monitor has been replaced by some new feature which you can find here.

How do I check whether a checkbox is checked in jQuery?

Though you have proposed a JavaScript solution for your problem (displaying a textbox when a checkbox is checked), this problem could be solved just by css. With this approach, your form works for users who have disabled JavaScript.

Assuming that you have the following HTML:

<label for="show_textbox">Show Textbox</label>
<input id="show_textbox" type="checkbox" />
<input type="text" />

You can use the following CSS to achieve the desired functionality:

 #show_textbox:not(:checked) + input[type=text] {display:none;}

For other scenarios, you may think of appropriate CSS selectors.

Here is a Fiddle to demonstrate this approach.

PostgreSQL : cast string to date DD/MM/YYYY

In case you need to convert the returned date of a select statement to a specific format you may use the following:

select to_char(DATE (*date_you_want_to_select*)::date, 'DD/MM/YYYY') as "Formated Date"

c# open a new form then close the current form?

I usually do this to switch back and forth between forms.

Firstly, in Program file I keep ApplicationContext and add a helper SwitchMainForm method.

        static class Program
    public static ApplicationContext AppContext { get;  set; }

    static void Main(string[] args)

        //Save app context
        Program.AppContext = new ApplicationContext(new LoginForm());

    //helper method to switch forms
      public static void SwitchMainForm(Form newForm)
        var oldMainForm = AppContext.MainForm;
        AppContext.MainForm = newForm;


Then anywhere in the code now I call SwitchMainForm method to switch easily to the new form.

// switch to some other form
var otherForm = new MyForm();

How to compare two maps by their values

If anyone is looking to do it in Java 8 streams below is the example.

import java.util.HashMap;
import java.util.Map;

public class CompareTwoMaps {

    public static void main(String[] args) {

        Map<String, String> a = new HashMap<>();
        a.put("foo", "bar" + "bar");
        a.put("zoo", "bar" + "bar");

        Map<String, String> b = new HashMap<>();
        b.put(new String("foo"), "bar" + "bar");
        b.put(new String("zoo"), "bar" + "bar");

        System.out.println("result = " + areEqual(a, b));

    private static boolean areEqual(Map<String, String> first, Map<String, String> second) {
        return first.entrySet().stream()
                .allMatch(e -> e.getValue().equals(second.get(e.getKey())));


For SQL Developer

You have to execute it manually


After that if you execute any procedure with DBMS_OUTPUT.PUT_LINE('info'); or directly .

This will print the line

And please don't try to add this


inside the definition of function and procedure, it will not compile and will not work.

How to implement OnFragmentInteractionListener

OnFragmentInteractionListener is the default implementation for handling fragment to activity communication. This can be implemented based on your needs. Suppose if you need a function in your activity to be executed during a particular action within your fragment, you may make use of this callback method. If you don't need to have this interaction between your hosting activity and fragment, you may remove this implementation.

In short you should implement the listener in your fragment hosting activity if you need the fragment-activity interaction like this

public class MainActivity extends Activity implements 
YourFragment.OnFragmentInteractionListener {..}

and your fragment should have it defined like this

public interface OnFragmentInteractionListener {
    // TODO: Update argument type and name
    void onFragmentInteraction(Uri uri);

also provide definition for void onFragmentInteraction(Uri uri); in your activity

or else just remove the listener initialisation from your fragment's onAttach if you dont have any fragment-activity interaction

Converting a PDF to PNG

Try to extract a single page.

$page = 4

gs -sDEVICE=pngalpha -dFirstPage="$page" -dLastPage="$page" -o thumb.png -r144 input.pdf

Android, How to create option Menu

public class MenuTest extends Activity {

    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(, menu);

        // return true so that the menu pop up is opened
        return true; 

and don't forget to press the menu button or icon on Emulator or device

Android set bitmap to Imageview

this code works with me

 ImageView carView = (ImageView) v.findViewById(;

                            byte[] decodedString = Base64.decode(picture, Base64.NO_WRAP);
                            InputStream input=new ByteArrayInputStream(decodedString);
                            Bitmap ext_pic = BitmapFactory.decodeStream(input);

How to get a value from the last inserted row?

If you're using JDBC 3.0, then you can get the value of the PK as soon as you inserted it.

Here's an article that talks about how :

Statement stmt = conn.createStatement();
// Obtain the generated key that results from the query.
stmt.executeUpdate("INSERT INTO authors " +
                   "(first_name, last_name) " +
                   "VALUES ('George', 'Orwell')",
ResultSet rs = stmt.getGeneratedKeys();
if ( ) {
    // Retrieve the auto generated key(s).
    int key = rs.getInt(1);

Overriding css style?

Instead of override you can add another class to the element and then you have an extra abilities. for example:


<div class="style1 style2"></div>


//only style for the first stylesheet
.style1 {
   width: 100%;      
//only style for second stylesheet
.style2 {
   width: 50%;     
//override all
.style1.style2 { 
   width: 70%;

Convert base64 png data to javascript file objects

You can create a Blob from your base64 data, and then read it asDataURL:

var img_b64 = canvas.toDataURL('image/png');
var png = img_b64.split(',')[1];

var the_file = new Blob([window.atob(png)],  {type: 'image/png', encoding: 'utf-8'});

var fr = new FileReader();
fr.onload = function ( oFREvent ) {
    var v =',')[1]; // encoding is messed up here, so we fix it
    v = atob(v);
    var good_b64 = btoa(decodeURIComponent(escape(v)));
    document.getElementById("uploadPreview").src = "data:image/png;base64," + good_b64;

Full example (includes junk code and console log):

Alternatively, you can use .readAsText, it works fine, and its more elegant.. but for some reason text does not sound right ;)

fr.onload = function ( oFREvent ) {
    document.getElementById("uploadPreview").src = "data:image/png;base64,"
    + btoa(;
fr.readAsText(the_file, "utf-8"); // its important to specify encoding here

Full example:

how to get the one entry from hashmap without iterating

Maps are not ordered, so there is no such thing as 'the first entry', and that's also why there is no get-by-index method on Map (or HashMap).

You could do this:

Map<String, String> map = ...;  // wherever you get this from

// Get the first entry that the iterator returns
Map.Entry<String, String> entry = map.entrySet().iterator().next();

(Note: Checking for an empty map omitted).

Your code doesn't get all the entries in the map, it returns immediately (and breaks out of the loop) with the first entry that's found.

To print the key and value of this first element:

System.out.println("Key: "+entry.getKey()+", Value: "+entry.getValue());

Note: Calling iterator() does not mean that you are iterating over the whole map.

Black transparent overlay on image hover with only CSS?

You can accomplish this by playing with the opacity of the image and setting the background color of the image to black. By making the image transparent, it will appear darker.

<div class="image">
    <img src="" alt="" />


.image { position: relative; border: 1px solid black; width: 200px; height: 200px; background: black; }
.image img { max-width: 100%; max-height: 100%; }
.image img:hover { opacity: .5 }

You might need to set the browser-specific opacity too to make this work in other browsers too.

How to add Python to Windows registry

I faced to the same problem. I solved it by

  1. navigate to HKEY_CURRENT_USER\Software\Python\PythonCore\3.4\InstallPath and edit the default key with the output of C:\> where python.exe command.
  2. navigate to HKEY_CURRENT_USER\Software\Python\PythonCore\3.4\InstallPath\InstallGroup and edit the default key with Python 3.4

Note: My python version is 3.4 and you need to replace 3.4 with your python version.

Normally you can find Registry entries for Python in HKEY_LOCAL_MACHINE\SOFTWARE\Python\PythonCore\<version>. You just need to copy those entries to HKEY_CURRENT_USER\Software\Python\PythonCore\<version>

Unable to start Service Intent

I hope I can help someone with this info as well: I moved my service class into another package and I fixed the references. The project was perfectly fine, BUT the service class could not be found by the activity.

By watching the log in logcat I noticed the warning about the issue: the activity could not find the service class, but the funny thing was that the package was incorrect, it contained a "/" char. The compiler was looking for


instead of


I moved the service class out from the package and back in and everything worked just fine.

Java Delegates?

Depending precisely what you mean, you can achieve a similar effect (passing around a method) using the Strategy Pattern.

Instead of a line like this declaring a named method signature:

// C#
public delegate void SomeFunction();

declare an interface:

// Java
public interface ISomeBehaviour {
   void SomeFunction();

For concrete implementations of the method, define a class that implements the behaviour:

// Java
public class TypeABehaviour implements ISomeBehaviour {
   public void SomeFunction() {
      // TypeA behaviour

public class TypeBBehaviour implements ISomeBehaviour {
   public void SomeFunction() {
      // TypeB behaviour

Then wherever you would have had a SomeFunction delegate in C#, use an ISomeBehaviour reference instead:

// C#
SomeFunction doSomething = SomeMethod;
doSomething = SomeOtherMethod;

// Java
ISomeBehaviour someBehaviour = new TypeABehaviour();
someBehaviour = new TypeBBehaviour();

With anonymous inner classes, you can even avoid declaring separate named classes and almost treat them like real delegate functions.

// Java
public void SomeMethod(ISomeBehaviour pSomeBehaviour) {


SomeMethod(new ISomeBehaviour() { 
   public void SomeFunction() {
      // your implementation

This should probably only be used when the implementation is very specific to the current context and wouldn't benefit from being reused.

And then of course in Java 8, these do become basically lambda expressions:

// Java 8
SomeMethod(() -> { /* your implementation */ });

Declaring array of objects

Depending on what you mean by declaring, you can try using object literals in an array literal:

var sample = [{}, {}, {} /*, ... */];

EDIT: If your goal is an array whose undefined items are empty object literals by default, you can write a small utility function:

function getDefaultObjectAt(array, index)
    return array[index] = array[index] || {};

Then use it like this:

var sample = [];
var obj = getDefaultObjectAt(sample, 0);     // {} returned and stored at index 0.

Or even:

getDefaultObjectAt(sample, 1).prop = "val";  // { prop: "val" } stored at index 1.

Of course, direct assignment to the return value of getDefaultObjectAt() will not work, so you cannot write:

getDefaultObjectAt(sample, 2) = { prop: "val" };

Pause Console in C++ program

There might be a best way (like using the portable cin.get()), but a good way doesn't exist. A program that has done its job should quit and give its resources back to the computer.

And yes, any usage of system() leads to unportable code, as the parameter is passed to the shell that owns your process.

Having pausing-code in your source code sooner or later causes hassles:

  • someone forgets to delete the pausing code before checking in
    • now all working mates have to wonder why the app does not close anymore
    • version history is tainted
  • #define is hell
  • it's annoying to anyone who runs your code from the console
  • it's very, very, very annoying when trying to start and end your program from within a script; quadly annoying if your program is part of a pipeline in the shell, because if the program does not end, the shell script or pipeline won't, too

Instead, explore your IDE. It probably has an option not to close the console window after running. If not, it's a great justification to you as a developer worth her/his money to always have a console window open nearby.

Alternatively, you can make this a program option, but I personally have never seen a program with an option --keep-alive-when-dead.

Moral of the story: This is the user's problem, and not the program's problem. Don't taint your code.

read complete file without using loop in java

If you are using Java 5/6, you can use Apache Commons IO for read file to string. The class contais several method for read files.

e.g. using the method FileUtils#readFileToString:

File file = new File("abc.txt");
String content = FileUtils.readFileToString(file);

Print list without brackets in a single row

print(', '.join(names))

This, like it sounds, just takes all the elements of the list and joins them with ', '.

How to stretch a table over multiple pages

You should \usepackage{longtable}.

Why boolean in Java takes only true or false? Why not 1 or 0 also?

On a related note: the java compiler uses int to represent boolean since JVM has a limited support for the boolean type.See Section 3.3.4 The boolean type.

In JVM, the integer zero represents false, and any non-zero integer represents true (Source : Inside Java Virtual Machine by Bill Venners)

How to print the values of slices

You could use a for loop to print the []Project as shown in @VonC excellent answer.

package main

import "fmt"

type Project struct{ name string }

func main() {
    projects := []Project{{"p1"}, {"p2"}}
    for i := range projects {
        p := projects[i]
        fmt.Println( //p1, p2

Vim 80 column layout concerns

I have this set up in my .vimrc:

highlight OverLength ctermbg=red ctermfg=white guibg=#592929
match OverLength /\%81v.\+/

This highlights the background in a subtle red for text that goes over the 80 column limit (subtle in GUI mode, anyway - in terminal mode it's less so).

How can I put a ListView into a ScrollView without it collapsing?

When we place ListView inside ScrollView two problems arise. One is ScrollView measures its children in UNSPECIFIED mode, so ListView sets its own height to accommodate only one item(I don't know why), another is ScrollView intercepts the touch event so ListView does not scrolls.

But we can place ListView inside ScrollView with some workaround. This post, by me, explains the workaround. By this workaround we can also retain ListView's recycling feature as well.

Change the Blank Cells to "NA"

Call dplyr package by installing from cran in r



It will convert all the blank cell in a particular column as NA

If the column contains "-", "", 0 like this change it in code according to the type of blank cell

E.g. if I get a blank cell like "" instead of "-", then use this code:

(file)$(colname)<-sub("", NA, file$colname)

How can I suppress the newline after a print statement?

print didn't transition from statement to function until Python 3.0. If you're using older Python then you can suppress the newline with a trailing comma like so:

print "Foo %10s bar" % baz,

How to read pdf file and write it to outputStream

You can use PdfBox from Apache which is simple to use and has good performance.

Here is an example of extracting text from a PDF file (you can read more here) :

import org.apache.pdfbox.pdmodel.*;
import org.apache.pdfbox.util.*;

public class PDFTest {

 public static void main(String[] args){
 PDDocument pd;
 BufferedWriter wr;
 try {
         File input = new File("C:\\Invoice.pdf");  // The PDF file from where you would like to extract
         File output = new File("C:\\SampleText.txt"); // The text file where you are going to store the extracted data
         pd = PDDocument.load(input);
         System.out.println(pd.isEncrypted());"CopyOfInvoice.pdf"); // Creates a copy called "CopyOfInvoice.pdf"
         PDFTextStripper stripper = new PDFTextStripper();
         wr = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(output)));
         stripper.writeText(pd, wr);
         if (pd != null) {
        // I use close() to flush the stream.
 } catch (Exception e){


You can get the text using PDFTextStripper:

PDFTextStripper reader = new PDFTextStripper();
String pageText = reader.getText(pd); // PDDocument object created

How to Convert date into MM/DD/YY format in C#

Look into using the ToString() method with a specified format.

Entity Framework code-first: migration fails with update-database, forces unneccessary(?) add-migration

When using VS2019, MVC5 - look under Migrations folder for file Configuration.cs Edit : AutomaticMigrationsEnabled = true


Parsing JSON with Unix tools

Now that Powershell is cross platform, I thought I'd throw its way out there, since I find it to be fairly intuitive and extremely simple.

curl -s '' | ConvertFrom-Json 

ConvertFrom-Json converts the JSON into a Powershell custom object, so you can easily work with the properties from that point forward. If you only wanted the 'id' property for example, you'd just do this:

curl -s '' | ConvertFrom-Json | select -ExpandProperty id

If you wanted to invoke the whole thing from within Bash, then you'd have to call it like this:

powershell 'curl -s "" | ConvertFrom-Json'

Of course there's a pure Powershell way to do it without curl, which would be:

Invoke-WebRequest '' | select -ExpandProperty Content | ConvertFrom-Json

Finally, there's also 'ConvertTo-Json' which converts a custom object to JSON just as easily. Here's an example:

(New-Object PsObject -Property @{ Name = "Tester"; SomeList = @('one','two','three')}) | ConvertTo-Json

Which would produce nice JSON like this:

"Name":  "Tester",
"SomeList":  [


Admittedly, using a Windows shell on Unix is somewhat sacrilegious but Powershell is really good at some things, and parsing JSON and XML are a couple of them. This the GitHub page for the cross platform version

Call Javascript onchange event by programmatically changing textbox value

You can put it in a different class and then call a function. This works when ajax refresh

$(document).on("change", ".inputQty", function(e) {

//Call a function(input,input);

Initializing C# auto-properties

This will be possible in C# 6.0:

public int Y { get; } = 2;

.net Core 2.0 - Package was restored using .NetFramework 4.6.1 instead of target framework .netCore 2.0. The package may not be fully compatible

The package is not fully compatible with dotnetcore 2.0 for now.

eg, for 'Microsoft.AspNet.WebApi.Client' it maybe supported in version (5.2.4). See Consume new Microsoft.AspNet.WebApi.Client.5.2.4 package for details.

You could try the standard Client package as Federico mentioned.

If that still not work, then as a workaround you can only create a Console App (.Net Framework) instead of the .net core 2.0 console app.

Reference this thread: Microsoft.AspNet.WebApi.Client supported in .NET Core or not?

Create a simple 10 second countdown

A solution using Promises, includes both progress bar & text countdown.

ProgressCountdown(10, 'pageBeginCountdown', 'pageBeginCountdownText').then(value => alert(`Page has started: ${value}.`));_x000D_
function ProgressCountdown(timeleft, bar, text) {_x000D_
  return new Promise((resolve, reject) => {_x000D_
    var countdownTimer = setInterval(() => {_x000D_
      document.getElementById(bar).value = timeleft;_x000D_
      document.getElementById(text).textContent = timeleft;_x000D_
      if (timeleft <= 0) {_x000D_
    }, 1000);_x000D_
<div class="row begin-countdown">_x000D_
  <div class="col-md-12 text-center">_x000D_
    <progress value="10" max="10" id="pageBeginCountdown"></progress>_x000D_
    <p> Begining in <span id="pageBeginCountdownText">10 </span> seconds</p>_x000D_

How to generate an MD5 file hash in JavaScript?

You could use crypto-js.

I would also recommend using SHA256, rather than MD5.

To install crypto-js via NPM:

npm install crypto-js

Alternatively you can use a CDN and reference the JS file.

Then to display a MD5 and SHA256 hash, you can do the following:

<script type="text/javascript">
    var md5Hash = CryptoJS.MD5("Test");
    var sha256Hash = CryptoJS.SHA256("Test1");


Working example located here, JSFiddle

There are also other JS functions that will generate an MD5 hash, outlined below.

function md5cycle(x, k) {
var a = x[0], b = x[1], c = x[2], d = x[3];

a = ff(a, b, c, d, k[0], 7, -680876936);
d = ff(d, a, b, c, k[1], 12, -389564586);
c = ff(c, d, a, b, k[2], 17,  606105819);
b = ff(b, c, d, a, k[3], 22, -1044525330);
a = ff(a, b, c, d, k[4], 7, -176418897);
d = ff(d, a, b, c, k[5], 12,  1200080426);
c = ff(c, d, a, b, k[6], 17, -1473231341);
b = ff(b, c, d, a, k[7], 22, -45705983);
a = ff(a, b, c, d, k[8], 7,  1770035416);
d = ff(d, a, b, c, k[9], 12, -1958414417);
c = ff(c, d, a, b, k[10], 17, -42063);
b = ff(b, c, d, a, k[11], 22, -1990404162);
a = ff(a, b, c, d, k[12], 7,  1804603682);
d = ff(d, a, b, c, k[13], 12, -40341101);
c = ff(c, d, a, b, k[14], 17, -1502002290);
b = ff(b, c, d, a, k[15], 22,  1236535329);

a = gg(a, b, c, d, k[1], 5, -165796510);
d = gg(d, a, b, c, k[6], 9, -1069501632);
c = gg(c, d, a, b, k[11], 14,  643717713);
b = gg(b, c, d, a, k[0], 20, -373897302);
a = gg(a, b, c, d, k[5], 5, -701558691);
d = gg(d, a, b, c, k[10], 9,  38016083);
c = gg(c, d, a, b, k[15], 14, -660478335);
b = gg(b, c, d, a, k[4], 20, -405537848);
a = gg(a, b, c, d, k[9], 5,  568446438);
d = gg(d, a, b, c, k[14], 9, -1019803690);
c = gg(c, d, a, b, k[3], 14, -187363961);
b = gg(b, c, d, a, k[8], 20,  1163531501);
a = gg(a, b, c, d, k[13], 5, -1444681467);
d = gg(d, a, b, c, k[2], 9, -51403784);
c = gg(c, d, a, b, k[7], 14,  1735328473);
b = gg(b, c, d, a, k[12], 20, -1926607734);

a = hh(a, b, c, d, k[5], 4, -378558);
d = hh(d, a, b, c, k[8], 11, -2022574463);
c = hh(c, d, a, b, k[11], 16,  1839030562);
b = hh(b, c, d, a, k[14], 23, -35309556);
a = hh(a, b, c, d, k[1], 4, -1530992060);
d = hh(d, a, b, c, k[4], 11,  1272893353);
c = hh(c, d, a, b, k[7], 16, -155497632);
b = hh(b, c, d, a, k[10], 23, -1094730640);
a = hh(a, b, c, d, k[13], 4,  681279174);
d = hh(d, a, b, c, k[0], 11, -358537222);
c = hh(c, d, a, b, k[3], 16, -722521979);
b = hh(b, c, d, a, k[6], 23,  76029189);
a = hh(a, b, c, d, k[9], 4, -640364487);
d = hh(d, a, b, c, k[12], 11, -421815835);
c = hh(c, d, a, b, k[15], 16,  530742520);
b = hh(b, c, d, a, k[2], 23, -995338651);

a = ii(a, b, c, d, k[0], 6, -198630844);
d = ii(d, a, b, c, k[7], 10,  1126891415);
c = ii(c, d, a, b, k[14], 15, -1416354905);
b = ii(b, c, d, a, k[5], 21, -57434055);
a = ii(a, b, c, d, k[12], 6,  1700485571);
d = ii(d, a, b, c, k[3], 10, -1894986606);
c = ii(c, d, a, b, k[10], 15, -1051523);
b = ii(b, c, d, a, k[1], 21, -2054922799);
a = ii(a, b, c, d, k[8], 6,  1873313359);
d = ii(d, a, b, c, k[15], 10, -30611744);
c = ii(c, d, a, b, k[6], 15, -1560198380);
b = ii(b, c, d, a, k[13], 21,  1309151649);
a = ii(a, b, c, d, k[4], 6, -145523070);
d = ii(d, a, b, c, k[11], 10, -1120210379);
c = ii(c, d, a, b, k[2], 15,  718787259);
b = ii(b, c, d, a, k[9], 21, -343485551);

x[0] = add32(a, x[0]);
x[1] = add32(b, x[1]);
x[2] = add32(c, x[2]);
x[3] = add32(d, x[3]);


function cmn(q, a, b, x, s, t) {
a = add32(add32(a, q), add32(x, t));
return add32((a << s) | (a >>> (32 - s)), b);

function ff(a, b, c, d, x, s, t) {
return cmn((b & c) | ((~b) & d), a, b, x, s, t);

function gg(a, b, c, d, x, s, t) {
return cmn((b & d) | (c & (~d)), a, b, x, s, t);

function hh(a, b, c, d, x, s, t) {
return cmn(b ^ c ^ d, a, b, x, s, t);

function ii(a, b, c, d, x, s, t) {
return cmn(c ^ (b | (~d)), a, b, x, s, t);

function md51(s) {
txt = '';
var n = s.length,
state = [1732584193, -271733879, -1732584194, 271733878], i;
for (i=64; i<=s.length; i+=64) {
md5cycle(state, md5blk(s.substring(i-64, i)));
s = s.substring(i-64);
var tail = [0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0];
for (i=0; i<s.length; i++)
tail[i>>2] |= s.charCodeAt(i) << ((i%4) << 3);
tail[i>>2] |= 0x80 << ((i%4) << 3);
if (i > 55) {
md5cycle(state, tail);
for (i=0; i<16; i++) tail[i] = 0;
tail[14] = n*8;
md5cycle(state, tail);
return state;

/* there needs to be support for Unicode here,
 * unless we pretend that we can redefine the MD-5
 * algorithm for multi-byte characters (perhaps
 * by adding every four 16-bit characters and
 * shortening the sum to 32 bits). Otherwise
 * I suggest performing MD-5 as if every character
 * was two bytes--e.g., 0040 0025 = @%--but then
 * how will an ordinary MD-5 sum be matched?
 * There is no way to standardize text to something
 * like UTF-8 before transformation; speed cost is
 * utterly prohibitive. The JavaScript standard
 * itself needs to look at this: it should start
 * providing access to strings as preformed UTF-8
 * 8-bit unsigned value arrays.
function md5blk(s) { /* I figured global was faster.   */
var md5blks = [], i; /* Andy King said do it this way. */
for (i=0; i<64; i+=4) {
md5blks[i>>2] = s.charCodeAt(i)
+ (s.charCodeAt(i+1) << 8)
+ (s.charCodeAt(i+2) << 16)
+ (s.charCodeAt(i+3) << 24);
return md5blks;

var hex_chr = '0123456789abcdef'.split('');

function rhex(n)
var s='', j=0;
for(; j<4; j++)
s += hex_chr[(n >> (j * 8 + 4)) & 0x0F]
+ hex_chr[(n >> (j * 8)) & 0x0F];
return s;

function hex(x) {
for (var i=0; i<x.length; i++)
x[i] = rhex(x[i]);
return x.join('');

function md5(s) {
return hex(md51(s));

/* this function is much faster,
so if possible we use it. Some IEs
are the only ones I know of that
need the idiotic second function,
generated by an if clause.  */

function add32(a, b) {
return (a + b) & 0xFFFFFFFF;

if (md5('hello') != '5d41402abc4b2a76b9719d911017c592') {
function add32(x, y) {
var lsw = (x & 0xFFFF) + (y & 0xFFFF),
msw = (x >> 16) + (y >> 16) + (lsw >> 16);
return (msw << 16) | (lsw & 0xFFFF);

Then simply use the MD5 function, as shown below:

alert(md5("Test string"));

Another working JS Fiddle here

Assign width to half available screen width declaratively

android:orientation="vertical" >
    android:text="Author : "
    android:textSize="20sp" />
    android:text="Edition : "
    android:textSize="20sp" />
    android:weightSum="1" >
        android:text="Edit" />
        android:text="Delete" />

Can clearInterval() be called inside setInterval()?

Yes you can. You can even test it:

var i = 0;_x000D_
var timer = setInterval(function() {_x000D_
  if (i === 5) clearInterval(timer);_x000D_
  console.log('post-interval'); //this will still run after clearing_x000D_
}, 200);

In this example, this timer clears when i reaches 5.

How to convert JSON object to JavaScript array?

This will solve the problem:

const json_data = {"2013-01-21":1,"2013-01-22":7};

const arr = Object.keys(json_data).map((key) => [key, json_data[key]]);


Or using Object.entries() method:


In both the cases, output will be:

/* output: 
[['2013-01-21', 1], ['2013-01-22', 7]]

How to install plugin for Eclipse from .zip

Seen here. You can unzip and

enter image description here enter image description here

Clicking Local will prefix your location fith file:/C:/etc/folder

You can Click archive instead and select your zip, as suggested in the second popular question. It will prefix with jar:// but it is not accepted by Eclipse itself. So, I used the plain folder solution.

Round up to Second Decimal Place in Python

def round_up(number, ndigits=None):
    # start by just rounding the number, as sometimes this rounds it up
    result = round(number, ndigits if ndigits else 0)
    if result < number:
        # whoops, the number was rounded down instead, so correct for that
        if ndigits:
            # use the type of number provided, e.g. float, decimal, fraction
            Numerical = type(number)
            # add the digit 1 in the correct decimal place
            result += Numerical(10) ** -ndigits
            # may need to be tweaked slightly if the addition was inexact
            result = round(result, ndigits)
            result += 1 # same as 10 ** -0 for precision of zero digits
    return result

assert round_up(0.022499999999999999, 2) == 0.03
assert round_up(0.1111111111111000, 2) == 0.12

assert round_up(1.11, 2) == 1.11
assert round_up(1e308, 2) == 1e308

MongoDB: How to find out if an array field contains an element?

I am trying to explain by putting problem statement and solution to it. I hope it will help

Problem Statement:

Find all the published products, whose name like ABC Product or PQR Product, and price should be less than 15/-


Below are the conditions that need to be taken care of

  1. Product price should be less than 15
  2. Product name should be either ABC Product or PQR Product
  3. Product should be in published state.

Below is the statement that applies above criterion to create query and fetch data.

$elements = $collection->find(
                [price] => Array( [$lt] => 15 ),
                [$or] => Array(
                                            [0] => ABC Product,
                                            [1]=> PQR Product

JQuery: How to get selected radio button value?

$('input[name=myradiobutton]:radio:checked') will get you the selected radio button $('input[name=myradiobutton]:radio:not(:checked)') will get you the unselected radio buttons

Using this you can do this


Update: After reading your Update I think I understand You will want to do something like this

var myRadioValue;

function radioValue(jqRadioButton){
  if (jqRadioButton.length) {
    myRadioValue = jqRadioButton.val();
  else {
    myRadioValue = 0;

$(document).ready(function () {
  $('input[name=myradiobutton]:radio').click(function () {   //Hook the click event for selected elements

  radioValue($('input[name=myradiobutton]:radio:checked')); //check for value on page load

Oracle REPLACE() function isn't handling carriage-returns & line-feeds

Ahah! Cade is on the money.

An artifact in TOAD prints \r\n as two placeholder 'blob' characters, but prints a single \r also as two placeholders. The 1st step toward a solution is to use ..

REPLACE( col_name, CHR(13) || CHR(10) )

.. but I opted for the slightly more robust ..

REPLACE(REPLACE( col_name, CHR(10) ), CHR(13) )

.. which catches offending characters in any order. My many thanks to Cade.


Transform DateTime into simple Date in Ruby on Rails

Try converting the entry to a string first. As long as the database column type is a date it will be formated as a date. || self.exif_date_time_original.to_s

How to extract the substring between two markers?

Using PyParsing

import pyparsing as pp

word = pp.Word(pp.alphanums)

s = 'gfgfdAAA1234ZZZuijjk'
rule = pp.nestedExpr('AAA', 'ZZZ')
for match in rule.searchString(s):

which yields:


React Native add bold or italics to single words in <Text> field

Use this react native library

To install

npm install react-native-htmlview --save

Basic Usage

 import React from 'react';
 import HTMLView from 'react-native-htmlview';

  class App extends React.Component {
  render() {
   const htmlContent = 'This is a sentence <b>with</b> one word in bold';

  return (
   />    );

Supports almost all html tags.

For more advanced usage like

  1. Link handling
  2. Custom Element Rendering

View this ReadMe

How to read integer values from text file

How large are the values? Java 6 has Scanner class that can read anything from int (32 bit), long (64-bit) to BigInteger (arbitrary big integer).

For Java 5 or 4, Scanner is there, but no support for BigInteger. You have to read line by line (with readLine of Scanner class) and create BigInteger object from the String.

Oracle SqlPlus - saving output in a file but don't show on screen

Try this:

spool M:\Documents\test;
select * from employees;
spool off;

Microsoft.Office.Core Reference Missing

I faced the same problem when i tried to open my old c# project into visual studio 2017 version. This problem arises typically when you try to open a project that you made with previous version of VS and open it with latest version. what i did is,i opened my project and delete the reference from my project,then added Microsoft outlook 12.0 object library and Microsoft office 12.0 object libraryMicrosoft outlook 12.0 object library

How to send post request with x-www-form-urlencoded body

As you set application/x-www-form-urlencoded as content type so data sent must be like this format.

String urlParameters  = "param1=data1&param2=data2&param3=data3";

Sending part now is quite straightforward.

byte[] postData = urlParameters.getBytes( StandardCharsets.UTF_8 );
int postDataLength = postData.length;
String request = "<Url here>";
URL url = new URL( request );
HttpURLConnection conn= (HttpURLConnection) url.openConnection();           
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); 
conn.setRequestProperty("charset", "utf-8");
conn.setRequestProperty("Content-Length", Integer.toString(postDataLength ));
try(DataOutputStream wr = new DataOutputStream(conn.getOutputStream())) {
   wr.write( postData );

Or you can create a generic method to build key value pattern which is required for application/x-www-form-urlencoded.

private String getDataString(HashMap<String, String> params) throws UnsupportedEncodingException{
    StringBuilder result = new StringBuilder();
    boolean first = true;
    for(Map.Entry<String, String> entry : params.entrySet()){
        if (first)
            first = false;
        result.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
        result.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
    return result.toString();

GCC -fPIC option

Code that is built into shared libraries should normally be position-independent code, so that the shared library can readily be loaded at (more or less) any address in memory. The -fPIC option ensures that GCC produces such code.

For div to extend full height

In case also setting the height of the html and the body to 100% makes everything messier for you as it did for me, the following worked for me:

height: calc(100vh - 33rem)

The - 33rem is the height of the elements coming after the one we want to take full height, i.e., 100vh. By subtracting the height, we will make sure there is no overflow and it will always be responsive (assuming we are working with rem instead of px).

pandas: best way to select all columns whose names start with X

Now that pandas' indexes support string operations, arguably the simplest and best way to select columns beginning with 'foo' is just:

df.loc[:, df.columns.str.startswith('foo')]

Alternatively, you can filter column (or row) labels with df.filter(). To specify a regular expression to match the names beginning with foo.:

>>> df.filter(regex=r'^foo\.', axis=1)
   foo.aa  foo.bars  foo.fighters foo.manchu
0     1.0         0             0        2         NA
1     2.1         0             1        4          0
2     NaN         0           NaN        1          0
3     4.7         0             0        0          0
4     5.6         0             0        0          0
5     6.8         1             0        5          0

To select only the required rows (containing a 1) and the columns, you can use loc, selecting the columns using filter (or any other method) and the rows using any:

>>> df.loc[(df == 1).any(axis=1), df.filter(regex=r'^foo\.', axis=1).columns]
   foo.aa  foo.bars  foo.fighters foo.manchu
0     1.0         0             0        2         NA
1     2.1         0             1        4          0
2     NaN         0           NaN        1          0
5     6.8         1             0        5          0

Java int to String - Integer.toString(i) vs new Integer(i).toString()

new Integer(i).toString() first creates a (redundant) wrapper object around i (which itself may be a wrapper object Integer).

Integer.toString(i) is preferred because it doesn't create any unnecessary objects.

Right HTTP status code to wrong input

409 Conflict could be an acceptable solution.

According to:

The request could not be completed due to a conflict with the current state of the resource. This code is only allowed in situations where it is expected that the user might be able to resolve the conflict and resubmit the request. The response body SHOULD include enough information for the user to recognize the source of the conflict. Ideally, the response entity would include enough information for the user or user agent to fix the problem; however, that might not be possible and is not required.

The doc continues with an example:

Conflicts are most likely to occur in response to a PUT request. For example, if versioning were being used and the entity being PUT included changes to a resource which conflict with those made by an earlier (third-party) request, the server might use the 409 response to indicate that it can't complete the request. In this case, the response entity would likely contain a list of the differences between the two versions in a format defined by the response Content-Type.

In my case, I would like to PUT a string, that must be unique, to a database via an API. Before adding it to the database, I am checking that it is not already in the database.

If it is, I will return "Error: The string is already in the database", 409.

I believe this is what the OP wanted: an error code suitable for when the data does not pass the server's criteria.

HttpClient - A task was cancelled?

Another possibility is that the result is not awaited on the client side. This can happen if any one method on the call stack does not use the await keyword to wait for the call to be completed.

Unable to install Maven on Windows: "JAVA_HOME is set to an invalid directory"

I was facing the same issue and just updated the JAVA_HOME worked for me.

previously it was like this: C:\Program Files\Java\jdk1.6.0_45\bin Just removed the \bin and it worked for me.

in a "using" block is a SqlConnection closed on return or exception?

In your first example, the C# compiler will actually translate the using statement to the following:

SqlConnection connection = new SqlConnection(connectionString));


    string storedProc = "GetData";
    SqlCommand command = new SqlCommand(storedProc, connection);
    command.CommandType = CommandType.StoredProcedure;
    command.Parameters.Add(new SqlParameter("@EmployeeID", employeeID));

    return (byte[])command.ExecuteScalar();

Finally statements will always get called before a function returns and so the connection will be always closed/disposed.

So, in your second example the code will be compiled to the following:


        string storedProc = "GetData";
        SqlCommand command = new SqlCommand(storedProc, connection);
        command.CommandType = CommandType.StoredProcedure;
        command.Parameters.Add(new SqlParameter("@EmployeeID", employeeID));

        return (byte[])command.ExecuteScalar();
catch (Exception)

The exception will be caught in the finally statement and the connection closed. The exception will not be seen by the outer catch clause.

WHERE clause on SQL Server "Text" data type

This works in MSSQL and MySQL:

FROM   Village
WHERE  CastleType LIKE '%foo%'; 

Why do I keep getting 'SVN: Working Copy XXXX locked; try performing 'cleanup'?

Solution: Step1: Have to remove “lock” file which present under “.svn” hidden file. Step2: In case if there is no “lock” file then you would see “we.db” you have to open this database and need to delete content alone from the following tables – lock – wc_lock Step3: Clean your project Step4: Try to commit now. Step5: Done.

How to bind inverse boolean properties in WPF?

Add one more property in your view model, which will return reverse value. And bind that to button. Like;

in view model:

public bool IsNotReadOnly{get{return !IsReadOnly;}}

in xaml:

IsEnabled="{Binding IsNotReadOnly"}

How do you find all subclasses of a given class in Java?

I know I'm a few years late to this party, but I came across this question trying to solve the same problem. You can use Eclipse's internal searching programatically, if you're writing an Eclipse Plugin (and thus take advantage of their caching, etc), to find classes which implement an interface. Here's my (very rough) first cut:

  protected void listImplementingClasses( String iface ) throws CoreException
    final IJavaProject project = <get your project here>;
      final IType ifaceType = project.findType( iface );
      final SearchPattern ifacePattern = SearchPattern.createPattern( ifaceType, IJavaSearchConstants.IMPLEMENTORS );
      final IJavaSearchScope scope = SearchEngine.createWorkspaceScope();
      final SearchEngine searchEngine = new SearchEngine();
      final LinkedList<SearchMatch> results = new LinkedList<SearchMatch>(); ifacePattern, 
      new SearchParticipant[]{ SearchEngine.getDefaultSearchParticipant() }, scope, new SearchRequestor() {

        public void acceptSearchMatch( SearchMatch match ) throws CoreException
          results.add( match );

      }, new IProgressMonitor() {

        public void beginTask( String name, int totalWork )

        public void done()
          System.out.println( results );

        public void internalWorked( double work )

        public boolean isCanceled()
          return false;

        public void setCanceled( boolean value )

        public void setTaskName( String name )

        public void subTask( String name )

        public void worked( int work )


    } catch( JavaModelException e )

The first problem I see so far is that I'm only catching classes which directly implement the interface, not all their subclasses - but a little recursion never hurt anyone.

How to align footer (div) to the bottom of the page?

Use <div style="position:fixed;bottom:0;height:auto;margin-top:40px;width:100%;text-align:center">I am footer</div>. Footer will not go upwards

How to add link to flash banner

@Michiel is correct to create a button but the code for ActionScript 3 it is a little different - where movieClipName is the name of your 'button'.

movieClipName.addEventListener(MouseEvent.CLICK, callLink);
function callLink:void {
  var url:String = "http://site";
  var request:URLRequest = new URLRequest(url);
  try {
    navigateToURL(request, '_blank');
  } catch (e:Error) {
    trace("Error occurred!");


When to use pthread_exit() and when to use pthread_join() in Linux?

You don't need any calls to pthread_exit(3) in your particular code.

In general, the main thread should not call pthread_exit, but should often call pthread_join(3) to wait for some other thread to finish.

In your PrintHello function, you don't need to call pthread_exit because it is implicit after returning from it.

So your code should rather be:

void *PrintHello(void *threadid)  {
  long tid = (long)threadid;
  printf("Hello World! It's me, thread #%ld!\n", tid);
  return threadid;

int main (int argc, char *argv[]) {
   pthread_t threads[NUM_THREADS];
   int rc;
   intptr_t t;
   // create all the threads
   for(t=0; t<NUM_THREADS; t++){
     printf("In main: creating thread %ld\n", (long) t);
     rc = pthread_create(&threads[t], NULL, PrintHello, (void *)t);
     if (rc) { fprintf(stderr, "failed to create thread #%ld - %s\n",
                                (long)t, strerror(rc));
   pthread_yield(); // useful to give other threads more chance to run
   // join all the threads
   for(t=0; t<NUM_THREADS; t++){
      printf("In main: joining thread #%ld\n", (long) t);
      rc = pthread_join(&threads[t], NULL);
      if (rc) { fprintf(stderr, "failed to join thread #%ld - %s\n",
                                (long)t, strerror(rc));

Should a 502 HTTP status code be used if a proxy receives no response at all?

Yes. Empty or incomplete headers or response body typically caused by broken connections or server side crash can cause 502 errors if accessed via a gateway or proxy.

For more information about the network errors

List Git commits not pushed to the origin yet

how to determine if a commit with particular hash have been pushed to the origin already?

# list remote branches that contain $commit
git branch -r --contains $commit

How to install an apk on the emulator in Android Studio?

For those using Mac and you get a command not found error, what you need to do is


./adb install "yourapk.apk"

enter image description here

Unix command to find lines common in two files

rm file3.txt

cat file1.out | while read line1
        cat file2.out | while read line2
                if [[ $line1 == $line2 ]]; then
                        echo $line1 >>file3.out

This should do it.

What is an API key?

It looks like that many people use API keys as a security solution. The bottom line is: Never treat API keys as secret it is not. On https or not, whoever can read the request can see the API key and can make whatever call they want. An API Key should be just as a 'user' identifier as its not a complete security solution even when used with ssl.

The better description is in Eugene Osovetsky link to: When working with most APIs, why do they require two types of authentication, namely a key and a secret? Or check

Executing <script> injected by innerHTML after AJAX call

Another thing to do is to load the page with a script such as:

<div id="content" onmouseover='myFunction();$(this).prop( 'onmouseover', null );'>
<script type="text/javascript">
function myFunction() {
  //do something

This will load the page, then run the script and remove the event handler when the function has been run. This will not run immediately after an ajax load, but if you are waiting for the user to enter the div element, this will work just fine.

PS. Requires Jquery

How to split a single column values to multiple column values?

I used it recently:

substring(name,1,charindex(' ',name)-1) as Col1,
substring(name,charindex(' ',name)+1,len(name)) as Col2 
from TableName

how to format date in Component of angular 5

You can find more information about the date pipe here, such as formats.

If you want to use it in your component, you can simply do

pipe = new DatePipe('en-US'); // Use your own locale

Now, you can simply use its transform method, which will be

const now =;
const myFormattedDate = this.pipe.transform(now, 'short');

Convert string to boolean in C#

You must use some of the C # conversion systems:

string to boolean: True to true

string str = "True";
bool mybool = System.Convert.ToBoolean(str);

boolean to string: true to True

bool mybool = true;
string str = System.Convert.ToString(mybool);


string str = mybool.ToString();

bool.Parse expects one parameter which in this case is str, even .

Convert.ToBoolean expects one parameter.

bool.TryParse expects two parameters, one entry (str) and one out (result).

If TryParse is true, then the conversion was correct, otherwise an error occurred

string str = "True";
bool MyBool = bool.Parse(str);


string str = "True";
if(bool.TryParse(str, out bool result))
   //Correct conversion
     //Incorrect, an error has occurred

How to get rid of the "No bootable medium found!" error in Virtual Box?

Follow the steps below:

1) Select your VM Instance. Go to Settings->Storage

2) Under the storage tree select the default image or "Empty"(which ever is present)

3) Under the attributes frame, click on the CD image and select "Choose a virtual CD/DVD disk file"

4) Browse and select the image file(iso or what ever format) from the system

5) Select OK.

Abishek's solution is correct. But the highlighted area in 2nd image could be misleading.

How to reload current page?

private router: Router


It will redirect to any pages without data lost (even current page). Data will remain as is.

Get a DataTable Columns DataType

You could always use typeof in the if statement. It is better than working with string values like the answer of Natarajan.

if (dt.Columns[0].DataType == typeof(DateTime))

How do I use MySQL through XAMPP?

XAMPP Apache + MariaDB + PHP + Perl (X -any OS)

  • After successful installation execute xampp-control.exe in XAMPP folder
  • Start Apache and MySQL enter image description here

  • Open browser and in url type localhost or

  • then you are welcomed with dashboard

By default your port is listing with 80.If you want you can change it to your desired port number in httpd.conf file.(If port 80 is already using with other app then you have to change it).

For example you changed port number 80 to 8090 then you can run as 'localhost:8090' or ''

Char array in a struct - incompatible assignment?

Or you could just use dynamic allocation, e.g.:

struct name {
  char *first;
  char *last;

struct name sara;
sara.first = "Sara";
sara.last = "Black";
printf("first: %s, last: %s\n", sara.first, sara.last);

Alphabet range in Python

In Python 2.7 and 3 you can use this:

import string


As @Zaz says: string.lowercase is deprecated and no longer works in Python 3 but string.ascii_lowercase works in both

How do I spool to a CSV formatted file using SQLPLUS?

You can explicitly format the query to produce a delimited string with something along the lines of:

select '"'||foo||'","'||bar||'"'
  from tab

And set up the output options as appropriate. As an option, the COLSEP variable on SQLPlus will let you produce delimited files without having to explicitly generate a string with the fields concatenated together. However, you will have to put quotes around strings on any columns that might contain embedded comma characters.

How to capture a JFrame's close button click event?


also works. First create a JFrame called frame, then add this code underneath.

How to access the local Django webserver from outside world

install ngrok in terminal

sudo apt-get install -y ngrok-client

after that run:

ngrok http 8000
ngrok http 

Add 2 hours to current time in MySQL?

The DATE_ADD() function will do the trick. (You can also use the ADDTIME() function if you're running at least v4.1.1.)

For your query, this would be:

FROM courses 
WHERE DATE_ADD(now(), INTERVAL 2 HOUR) > start_time


FROM courses 
WHERE ADDTIME(now(), '02:00:00') > start_time

What's the difference between RANK() and DENSE_RANK() functions in oracle?

Rank and Dense rank gives the rank in the partitioned dataset.

Rank() : It doesn't give you consecutive integer numbers.

Dense_rank() : It gives you consecutive integer numbers.

enter image description here

In above picture , the rank of 10008 zip is 2 by dense_rank() function and 24 by rank() function as it considers the row_number.

Linux command for extracting war file?


jar xvf myproject.war

jQuery Call to WebService returns "No Transport" error

I solved it simply by removing the domain from the request url.


After: /_vti_bin/service.svc

How to prevent a click on a '#' link from jumping to top of page?

You could just pass an anchor tag without an href property, and use jQuery to do the required action:

<a class="foo">bar</a>

Go back button in a page

Here is the code

<input type="button" value="Back" onclick="window.history.back()" /> 

How do I use su to execute the rest of the bash script as that user?

Use sudo instead

EDIT: As Douglas pointed out, you can not use cd in sudo since it is not an external command. You have to run the commands in a subshell to make the cd work.

sudo -u $USERNAME -H sh -c "cd ~/$PROJECT; svn update"

sudo -u $USERNAME -H cd ~/$PROJECT
sudo -u $USERNAME svn update

You may be asked to input that user's password, but only once.

Usages of doThrow() doAnswer() doNothing() and doReturn() in mockito

It depends on the kind of test double you want to interact with:

  • If you don't use doNothing and you mock an object, the real method is not called
  • If you don't use doNothing and you spy an object, the real method is called

In other words, with mocking the only useful interactions with a collaborator are the ones that you provide. By default functions will return null, void methods do nothing.

Execute a command line binary with Node.js

If you don't mind a dependency and want to use promises, child-process-promise works:


npm install child-process-promise --save

exec Usage

var exec = require('child-process-promise').exec;

exec('echo hello')
    .then(function (result) {
        var stdout = result.stdout;
        var stderr = result.stderr;
        console.log('stdout: ', stdout);
        console.log('stderr: ', stderr);
    .catch(function (err) {
        console.error('ERROR: ', err);

spawn usage

var spawn = require('child-process-promise').spawn;

var promise = spawn('echo', ['hello']);

var childProcess = promise.childProcess;

console.log('[spawn] ',;
childProcess.stdout.on('data', function (data) {
    console.log('[spawn] stdout: ', data.toString());
childProcess.stderr.on('data', function (data) {
    console.log('[spawn] stderr: ', data.toString());

promise.then(function () {
        console.log('[spawn] done!');
    .catch(function (err) {
        console.error('[spawn] ERROR: ', err);

The difference between "require(x)" and "import x"

The major difference between require and import, is that require will automatically scan node_modules to find modules, but import, which comes from ES6, won't.

Most people use babel to compile import and export, which makes import act the same as require.

The future version of Node.js might support import itself (actually, the experimental version already does), and judging by Node.js' notes, import won't support node_modules, it base on ES6, and must specify the path of the module.

So I would suggest you not use import with babel, but this feature is not yet confirmed, it might support node_modules in the future, who would know?

For reference, below is an example of how babel can convert ES6's import syntax to CommonJS's require syntax.

Say the fileapp_es6.js contains this import:

import format from 'date-fns/format';

This is a directive to import the format function from the node package date-fns.

The related package.json file could contain something like this:

"scripts": {
    "start": "node app.js",
    "build-server-file": "babel app_es6.js --out-file app.js",
    "webpack": "webpack"

The related .babelrc file could be something like this:

    "presets": [
                    "node": "current"

This build-server-file script defined in the package.json file is a directive for babel to parse the app_es6.js file and output the file app.js.

After running the build-server-file script, if you open app.js and look for the date-fns import, you will see it has been converted into this:

var _format = require("date-fns/format");

var _format2 = _interopRequireDefault(_format);

Most of that file is gobbledygook to most humans, however computers understand it.

Also for reference, as an example of how a module can be created and imported into your project, if you install date-fns and then open node_modules/date-fns/get_year/index.js you can see it contains:

var parse = require('../parse/index.js')

function getYear (dirtyDate) {
  var date = parse(dirtyDate)
  var year = date.getFullYear()
  return year

module.exports = getYear

Using the babel process above, your app_es6.js file could then contain:

import getYear from 'date-fns/get_year';

// Which year is 2 July 2014?
var result = getYear(new Date(2014, 6, 2))
//=> 2014

And babel would convert the imports to:

var _get_year = require("date-fns/get_year");

var _get_year2 = _interopRequireDefault(_get_year);

And handle all references to the function accordingly.

Skipping Incompatible Libraries at compile

That message isn't actually an error - it's just a warning that the file in question isn't of the right architecture (e.g. 32-bit vs 64-bit, wrong CPU architecture). The linker will keep looking for a library of the right type.

Of course, if you're also getting an error along the lines of can't find lPI-Http then you have a problem :-)

It's hard to suggest what the exact remedy will be without knowing the details of your build system and makefiles, but here are a couple of shots in the dark:

  1. Just to check: usually you would add flags to CFLAGS rather than CTAGS - are you sure this is correct? (What you have may be correct - this will depend on your build system!)
  2. Often the flag needs to be passed to the linker too - so you may also need to modify LDFLAGS

If that doesn't help - can you post the full error output, plus the actual command (e.g. gcc foo.c -m32 -Dxxx etc) that was being executed?

How do Python functions handle the types of the parameters that you pass in?

Python is strongly typed because every object has a type, every object knows its type, it's impossible to accidentally or deliberately use an object of a type "as if" it was an object of a different type, and all elementary operations on the object are delegated to its type.

This has nothing to do with names. A name in Python doesn't "have a type": if and when a name's defined, the name refers to an object, and the object does have a type (but that doesn't in fact force a type on the name: a name is a name).

A name in Python can perfectly well refer to different objects at different times (as in most programming languages, though not all) -- and there is no constraint on the name such that, if it has once referred to an object of type X, it's then forevermore constrained to refer only to other objects of type X. Constraints on names are not part of the concept of "strong typing", though some enthusiasts of static typing (where names do get constrained, and in a static, AKA compile-time, fashion, too) do misuse the term this way.

android on Text Change Listener

We can remove the TextWatcher for a field just before editing its text then add it back after editing the text.

Declare Text Watchers for both field1 and field2 as separate variables to give them a name: e.g. for field1

private TextWatcher Field_1_Watcher = new TextWatcher() {
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {

    public void afterTextChanged(Editable s) {

    public void onTextChanged(CharSequence s, int start, int before, int count) {



then add the watcher using its name: field1.addTextChangedListener(Field_1_Watcher) for field1, and field2.addTextChangedListener(Field_2_Watcher) for field2

Before changing the field2 text remove the TextWatcher: field2.removeTextChangedListener(Field_2_Watcher) change the text: field2.setText("")

then add the TextWatcher back: field2.addTextChangedListener(Field_2_Watcher)

Do the same for the other field

Is the MIME type 'image/jpg' the same as 'image/jpeg'?

For those it might help, I use this list as a reference to define my content-type when I have to deal with images on my app.

It says that jpg extension can be declared with Content-type : image/jpeg

There isn't any image/jpg attribute for content-type.

Is there any way to wait for AJAX response and halt execution?

Method 1:

function functABC(){
        url: 'myPage.php',
        data: {id: id},
        success: function(data) {
            return data;
        complete: function(){
              // do the job here

var response = functABC();

Method 2

function functABC(){
        url: 'myPage.php',
        data: {id: id},
        async: false,
        success: function(data) {
            return data;

   // do the job here

Cannot execute script: Insufficient memory to continue the execution of the program

If you need to connect to LocalDB during development, you can use:

sqlcmd -S "(localdb)\MSSQLLocalDB" -d dbname -i file.sql

Using OR operator in a jquery if statement

Update: using .indexOf() to detect if stat value is one of arr elements

Pure JavaScript

var arr = [20,30,40,50,60,70,80,90,100];_x000D_
//or detect equal to all_x000D_
//var arr = [10,10,10,10,10,10,10];_x000D_
    var stat = 10;_x000D_
if(arr.indexOf(stat)==-1)alert("stat is not equal to one more elements of array");

What programming language does facebook use?

The language used by Facebook is PHP.

Also, do any other social networking sites use the same language?

The other one I know of is friendster.

How do I set multipart in axios with react?

If you are sending alphanumeric data try changing

'Content-Type': 'multipart/form-data'


'Content-Type': 'application/x-www-form-urlencoded'

If you are sending non-alphanumeric data try to remove 'Content-Type' at all.

If it still does not work, consider trying request-promise (at least to test whether it is really axios problem or not)

Using File.listFiles with FileNameExtensionFilter

The FileNameExtensionFilter class is intended for Swing to be used in a JFileChooser.

Try using a FilenameFilter instead. For example:

File dir = new File("/users/blah/dirname");
File[] files = dir.listFiles(new FilenameFilter() {
    public boolean accept(File dir, String name) {
        return name.toLowerCase().endsWith(".txt");

Multiple IF statements between number ranges

Shorter than accepted A, easily extensible and addresses 0 and below:

=if(or(A2<=0,A2>2000),"?",if(A2<500,"Less than 500","Between "&500*int(A2/500)&" and "&500*(int(A2/500)+1))) 

Crontab Day of the Week syntax

    :-) Sunday    |    0  ->  Sun
        Monday    |    1  ->  Mon
       Tuesday    |    2  ->  Tue
     Wednesday    |    3  ->  Wed
      Thursday    |    4  ->  Thu
        Friday    |    5  ->  Fri
      Saturday    |    6  ->  Sat
    :-) Sunday    |    7  ->  Sun

As you can see above, and as said before, the numbers 0 and 7 are both assigned to Sunday. There are also the English abbreviated days of the week listed, which can also be used in the crontab.

Examples of Number or Abbreviation Use

15 09 * * 5,6,0             command
15 09 * * 5,6,7             command
15 09 * * 5-7               command
15 09 * * Fri,Sat,Sun       command

The four examples do all the same and execute a command every Friday, Saturday, and Sunday at 9.15 o'clock.

In Detail

Having two numbers 0 and 7 for Sunday can be useful for writing weekday ranges starting with 0 or ending with 7. So you can write ranges starting with Sunday or ending with it, like 0-2 or 5-7 for example (ranges must start with the lower number and must end with the higher). The abbreviations cannot be used to define a weekday range.

How can I output the value of an enum class in C++11

Following worked for me in C++11:

template <typename Enum>
constexpr typename std::enable_if<std::is_enum<Enum>::value,
                                  typename std::underlying_type<Enum>::type>::type
to_integral(Enum const& value) {
    return static_cast<typename std::underlying_type<Enum>::type>(value);