How to JUnit test that two List<E> contain the same elements in the same order?
org.junit.Assert.assertEquals()
and org.junit.Assert.assertArrayEquals()
do the job.
To avoid next questions: If you want to ignore the order put all elements to set and then compare: Assert.assertEquals(new HashSet<String>(one), new HashSet<String>(two))
If however you just want to ignore duplicates but preserve the order wrap you list with LinkedHashSet
.
Yet another tip. The trick Assert.assertEquals(new HashSet<String>(one), new HashSet<String>(two))
works fine until the comparison fails. In this case it shows you error message with to string representations of your sets that can be confusing because the order in set is almost not predictable (at least for complex objects). So, the trick I found is to wrap the collection with sorted set instead of HashSet
. You can use TreeSet
with custom comparator.
How to get the <html> tag HTML with JavaScript / jQuery?
This is how to get the html DOM element purely with JS:
var htmlElement = document.getElementsByTagName("html")[0];
or
var htmlElement = document.querySelector("html");
And if you want to use jQuery to get attributes from it...
$(htmlElement).attr(INSERT-ATTRIBUTE-NAME);
How do I send a cross-domain POST request via JavaScript?
If you control the remote server, you should probably use CORS, as described in this answer; it's supported in IE8 and up, and all recent versions of FF, GC, and Safari. (But in IE8 and 9, CORS won't allow you to send cookies in the request.)
So, if you don't control the remote server, or if you have to support IE7, or if you need cookies and you have to support IE8/9, you'll probably want to use an iframe technique.
- Create an iframe with a unique name. (iframes use a global namespace for the entire browser, so pick a name that no other website will use.)
- Construct a form with hidden inputs, targeting the iframe.
- Submit the form.
Here's sample code; I tested it on IE6, IE7, IE8, IE9, FF4, GC11, S5.
function crossDomainPost() {
// Add the iframe with a unique name
var iframe = document.createElement("iframe");
var uniqueString = "CHANGE_THIS_TO_SOME_UNIQUE_STRING";
document.body.appendChild(iframe);
iframe.style.display = "none";
iframe.contentWindow.name = uniqueString;
// construct a form with hidden inputs, targeting the iframe
var form = document.createElement("form");
form.target = uniqueString;
form.action = "http://INSERT_YOUR_URL_HERE";
form.method = "POST";
// repeat for each parameter
var input = document.createElement("input");
input.type = "hidden";
input.name = "INSERT_YOUR_PARAMETER_NAME_HERE";
input.value = "INSERT_YOUR_PARAMETER_VALUE_HERE";
form.appendChild(input);
document.body.appendChild(form);
form.submit();
}
Beware! You won't be able to directly read the response of the POST, since the iframe exists on a separate domain. Frames aren't allowed to communicate with each other from different domains; this is the same-origin policy.
If you control the remote server but you can't use CORS (e.g. because you're on IE8/IE9 and you need to use cookies), there are ways to work around the same-origin policy, for example by using window.postMessage
and/or one of a number of libraries allowing you to send cross-domain cross-frame messages in older browsers:
If you don't control the remote server, then you can't read the response of the POST, period. It would cause security problems otherwise.
jQuery attr('onclick')
As @Richard pointed out above, the onClick needs to have a capital 'C'.
$('#stop').click(function() {
$('next').attr('onClick','stopMoving()');
}
Avoid printStackTrace(); use a logger call instead
A production quality program should use one of the many logging alternatives (e.g. log4j, logback, java.util.logging) to report errors and other diagnostics. This has a number of advantages:
- Log messages go to a configurable location.
- The end user doesn't see the messages unless you configure the logging so that he/she does.
- You can use different loggers and logging levels, etc to control how much little or much logging is recorded.
- You can use different appender formats to control what the logging looks like.
- You can easily plug the logging output into a larger monitoring / logging framework.
- All of the above can be done without changing your code; i.e. by editing the deployed application's logging config file.
By contrast, if you just use printStackTrace, the deployer / end user has little if any control, and logging messages are liable to either be lost or shown to the end user in inappropriate circumstances. (And nothing terrifies a timid user more than a random stack trace.)
What are Covering Indexes and Covered Queries in SQL Server?
If all the columns requested in the select
list of query, are available in the index, then the query engine doesn't have to lookup the table again which can significantly increase the performance of the query. Since all the requested columns are available with in the index, the index is covering the query. So, the query is called a covering query and the index is a covering index.
A clustered index can always cover a query, if the columns in the select list are from the same table.
The following links can be helpful, if you are new to index concepts:
Find the index of a dict within a list, by matching the dict's value
Here's a function that finds the dictionary's index position if it exists.
dicts = [{'id':'1234','name':'Jason'},
{'id':'2345','name':'Tom'},
{'id':'3456','name':'Art'}]
def find_index(dicts, key, value):
class Null: pass
for i, d in enumerate(dicts):
if d.get(key, Null) == value:
return i
else:
raise ValueError('no dict with the key and value combination found')
print find_index(dicts, 'name', 'Tom')
# 1
find_index(dicts, 'name', 'Ensnare')
# ValueError: no dict with the key and value combination found
Most efficient conversion of ResultSet to JSON?
the other way , here I have used ArrayList and Map, so its not call json object row by row but after iteration of resultset finished :
List<Map<String, String>> list = new ArrayList<Map<String, String>>();
ResultSetMetaData rsMetaData = rs.getMetaData();
while(rs.next()){
Map map = new HashMap();
for (int i = 1; i <= rsMetaData.getColumnCount(); i++) {
String key = rsMetaData.getColumnName(i);
String value = null;
if (rsmd.getColumnType(i) == java.sql.Types.VARCHAR) {
value = rs.getString(key);
} else if(rsmd.getColumnType(i)==java.sql.Types.BIGINT)
value = rs.getLong(key);
}
map.put(key, value);
}
list.add(map);
}
json.put(list);
How do I convert Long to byte[] and back in java
public static long bytesToLong(byte[] bytes) {
if (bytes.length > 8) {
throw new IllegalMethodParameterException("byte should not be more than 8 bytes");
}
long r = 0;
for (int i = 0; i < bytes.length; i++) {
r = r << 8;
r += bytes[i];
}
return r;
}
public static byte[] longToBytes(long l) {
ArrayList<Byte> bytes = new ArrayList<Byte>();
while (l != 0) {
bytes.add((byte) (l % (0xff + 1)));
l = l >> 8;
}
byte[] bytesp = new byte[bytes.size()];
for (int i = bytes.size() - 1, j = 0; i >= 0; i--, j++) {
bytesp[j] = bytes.get(i);
}
return bytesp;
}
How to update fields in a model without creating a new record in django?
Sometimes it may be required to execute the update atomically that is using one update request to the database without reading it first.
Also get
-set attribute
-save
may cause problems if such updates may be done concurrently or if you need to set the new value based on the old field value.
In such cases query expressions together with update
may by useful:
TemperatureData.objects.filter(id=1).update(value=F('value') + 1)
Find and Replace text in the entire table using a MySQL query
the best you export it as sql file and open it with editor such as visual studio code and find and repalace your words.
i replace in 1 gig file sql in 1 minutes for 16 word that total is 14600 word.
its the best way.
and after replace it save and import it again.
do not forget compress it with zip for import.
NodeJS - What does "socket hang up" actually mean?
After a long debug into node js code, mongodb connection string, checking CORS etc, For me just switching to a different port number server.listen(port);
made it work, into postman
, try that too. No changes to proxy
settings just the defaults.
What techniques can be used to speed up C++ compilation times?
Not about the compilation time, but about the build time:
Use ccache if you have to rebuild the same files when you are working
on your buildfiles
Use ninja-build instead of make. I am currently compiling a project
with ~100 source files and everything is cached by ccache. make needs
5 minutes, ninja less than 1.
You can generate your ninja files from cmake with -GNinja
.
What is a 'workspace' in Visual Studio Code?
You can save settings at the workspace level and you can open multiple folders in a workspace. If you want to do either of those things, use a workspace, otherwise, just open a folder.
A Visual Studio Code workspace is a list of a project's folders and files. A workspace can contain multiple folders. You can customize the settings and preferences of a workspace.
EditorFor() and html properties
UPDATE: hm, obviously this won't work because model is passed by value so attributes are not preserved; but I leave this answer as an idea.
Another solution, I think, would be to add your own TextBox/etc helpers, that will check for your own attributes on model.
public class ViewModel
{
[MyAddAttribute("class", "myclass")]
public string StringValue { get; set; }
}
public class MyExtensions
{
public static IDictionary<string, object> GetMyAttributes(object model)
{
// kind of prototype code...
return model.GetType().GetCustomAttributes(typeof(MyAddAttribute)).OfType<MyAddAttribute>().ToDictionary(
x => x.Name, x => x.Value);
}
}
<!-- in the template -->
<%= Html.TextBox("Name", Model, MyExtensions.GetMyAttributes(Model)) %>
This one is easier but not as convinient/flexible.
ASP.net Repeater get current index, pointer, or counter
Add a label control to your Repeater's ItemTemplate. Handle OnItemCreated event.
ASPX
<asp:Repeater ID="rptr" runat="server" OnItemCreated="RepeaterItemCreated">
<ItemTemplate>
<div id="width:50%;height:30px;background:#0f0a0f;">
<asp:Label ID="lblSr" runat="server"
style="width:30%;float:left;text-align:right;text-indent:-2px;" />
<span
style="width:65%;float:right;text-align:left;text-indent:-2px;" >
<%# Eval("Item") %>
</span>
</div>
</ItemTemplate>
</asp:Repeater>
Code Behind:
protected void RepeaterItemCreated(object sender, RepeaterItemEventArgs e)
{
Label l = e.Item.FindControl("lblSr") as Label;
if (l != null)
l.Text = e.Item.ItemIndex + 1+"";
}
Could not install packages due to an EnvironmentError: [Errno 13]
The answer is in the error message. In the past you or a process did a sudo pip
and that caused some of the directories under /Library/Python/2.7/site-packages/...
to have permissions that make it unaccessable to your current user.
Then you did a pip install whatever
which relies on the other thing.
So to fix it, visit the /Library/Python/2.7/site-packages/... and find the directory with the root or not-your-user permissions and either remove then reinstall those packages, or just force ownership to the user to whom ought to have access.
JavaScript null check
Q: The function was called with no arguments, thus making data an undefined variable, and raising an error on data != null.
A: Yes, data
will be set to undefined. See section 10.5 Declaration Binding Instantiation of the spec. But accessing an undefined value does not raise an error. You're probably confusing this with accessing an undeclared variable in strict mode which does raise an error.
Q: The function was called specifically with null (or undefined), as its argument, in which case data != null already protects the inner code, rendering && data !== undefined useless.
Q: The function was called with a non-null argument, in which case it will trivially pass both data != null and data !== undefined.
A: Correct. Note that the following tests are equivalent:
data != null
data != undefined
data !== null && data !== undefined
See section 11.9.3 The Abstract Equality Comparison Algorithm and section 11.9.6 The Strict Equality Comparison Algorithm of the spec.
How to use subList()
You could use streams in Java 8. To always get 10 entries at the most, you could do:
dataList.stream().skip(5).limit(10).collect(Collectors.toList());
dataList.stream().skip(30).limit(10).collect(Collectors.toList());
What requests do browsers' "F5" and "Ctrl + F5" refreshes generate?
When user press F5 although new request goes to web server and get a responce for the request as well. But when the responce header is Parsed it check the required information in browser cache. If the required information in cache has not expired then that information is restored from in cache itself.
When user click on CTRL-F5 even then new request goes to web server and get a responce. But this time when the responce header is Parsed it do not check any required information in cache, and bring all updated information form server only.
Debugging PHP Mail() and/or PHPMailer
It looks like the class.phpmailer.php file is corrupt. I would download the latest version and try again.
I've always used phpMailer's SMTP feature:
$mail->IsSMTP();
$mail->Host = "localhost";
And if you need debug info:
$mail->SMTPDebug = 2; // enables SMTP debug information (for testing)
// 1 = errors and messages
// 2 = messages only
SQL Server Group by Count of DateTime Per Hour?
Alternatively, just GROUP BY
the hour and day:
SELECT CAST(Startdate as DATE) as 'StartDate',
CAST(DATEPART(Hour, StartDate) as varchar) + ':00' as 'Hour',
COUNT(*) as 'Ct'
FROM #Events
GROUP BY CAST(Startdate as DATE), DATEPART(Hour, StartDate)
ORDER BY CAST(Startdate as DATE) ASC
output:
StartDate Hour Ct
2007-01-01 0:00 3
2007-01-02 5:00 2
2007-01-03 4:00 1
2007-01-07 3:00 1
gnuplot - adjust size of key/legend
To adjust the length of the samples:
set key samplen X
(default is 4)
To adjust the vertical spacing of the samples:
set key spacing X
(default is 1.25)
and (for completeness), to adjust the fontsize:
set key font "<face>,<size>"
(default depends on the terminal)
And of course, all these can be combined into one line:
set key samplen 2 spacing .5 font ",8"
Note that you can also change the position of the key using set key at <position>
or any one of the pre-defined positions (which I'll just defer to help key
at this point)
Get domain name
I'm going to add an answer to try to clear up a few things here as there seems to be some confusion. The main issue is that people are asking the wrong question, or at least not being specific enough.
What does a computer's "domain" actually mean?
When we talk about a computer's "domain", there are several things that we might be referring to. What follows is not an exhaustive list, but it covers the most common cases:
- A user or computer security principal may belong to an Active Directory domain.
- The network stack's primary DNS search suffix may be referred to as the computer's "domain".
- A DNS name that resolves to the computer's IP address may be referred to as the computer's "domain".
Which one do I want?
This is highly dependent on what you are trying to do. The original poster of this question was looking for the computer's "Active Directory domain", which probably means they are looking for the domain to which either the computer's security principal or a user's security principal belongs. Generally you want these when you are trying to talk to Active Directory in some way. Note that the current user principal and the current computer principal are not necessarily in the same domain.
Pieter van Ginkel's answer is actually giving you the local network stack's primary DNS suffix (the same thing that's shown in the top section of the output of ipconfig /all
). In the 99% case, this is probably the same as the domain to which both the computer's security principal and the currently authenticated user's principal belong - but not necessarily. Generally this is what you want when you are trying to talk to devices on the LAN, regardless of whether or not the devices are anything to do with Active Directory. For many applications, this will still be a "good enough" answer for talking to Active Directory.
The last option, a DNS name, is a lot fuzzier and more ambiguous than the other two. Anywhere between zero and infinity DNS records may resolve to a given IP address - and it's not necessarily even clear which IP address you are interested in. user2031519's answer refers to the value of HTTP_HOST
, which is specifically useful when determining how the user resolved your HTTP server in order to send the request you are currently processing. This is almost certainly not what you want if you are trying to do anything with Active Directory.
How do I get them?
Domain of the current user security principal
This one's nice and simple, it's what Tim's answer is giving you.
System.Environment.UserDomainName
Domain of the current computer security principal
This is probably what the OP wanted, for this one we're going to have to ask Active Directory about it.
System.DirectoryServices.ActiveDirectory.Domain.GetComputerDomain()
This one will throw a ActiveDirectoryObjectNotFoundException
if the local machine is not part of domain, or the domain controller cannot be contacted.
Network stack's primary DNS suffix
This is what Pieter van Ginkel's answer is giving you. It's probably not exactly what you want, but there's a good chance it's good enough for you - if it isn't, you probably already know why.
System.Net.NetworkInformation.IPGlobalProperties.GetIPGlobalProperties().DomainName
DNS name that resolves to the computer's IP address
This one's tricky and there's no single answer to it. If this is what you are after, comment below and I will happily discuss your use-case and help you to work out the best solution (and expand on this answer in the process).
Bootstrap with jQuery Validation Plugin
for total compatibility with twitter bootstrap 3, I need to override some plugins methods:
// override jquery validate plugin defaults
$.validator.setDefaults({
highlight: function(element) {
$(element).closest('.form-group').addClass('has-error');
},
unhighlight: function(element) {
$(element).closest('.form-group').removeClass('has-error');
},
errorElement: 'span',
errorClass: 'help-block',
errorPlacement: function(error, element) {
if(element.parent('.input-group').length) {
error.insertAfter(element.parent());
} else {
error.insertAfter(element);
}
}
});
See Example: http://jsfiddle.net/mapb_1990/hTPY7/7/
How to install "ifconfig" command in my ubuntu docker image?
From within a Dockerfile something like the following should do the trick:
RUN apt-get update && \
apt-get install -y net-tools
From memory it's best practice to combine the update and the package installation lines to prevent docker caching the update step which can result in out-dated packages being installed.
Installing it via the CLI or a shell script:
apt-get update && apt-get install net-tools
How do you compare two version Strings in Java?
@alex's post on Kotlin
class Version(inputVersion: String) : Comparable<Version> {
var version: String
private set
override fun compareTo(other: Version) =
(split() to other.split()).let {(thisParts, thatParts)->
val length = max(thisParts.size, thatParts.size)
for (i in 0 until length) {
val thisPart = if (i < thisParts.size) thisParts[i].toInt() else 0
val thatPart = if (i < thatParts.size) thatParts[i].toInt() else 0
if (thisPart < thatPart) return -1
if (thisPart > thatPart) return 1
}
0
}
init {
require(inputVersion.matches("[0-9]+(\\.[0-9]+)*".toRegex())) { "Invalid version format" }
version = inputVersion
}
}
fun Version.split() = version.split(".").toTypedArray()
usage:
Version("1.2.4").compareTo(Version("0.0.5")) //return 1
Remove all special characters, punctuation and spaces from string
This can be done without regex:
>>> string = "Special $#! characters spaces 888323"
>>> ''.join(e for e in string if e.isalnum())
'Specialcharactersspaces888323'
You can use str.isalnum
:
S.isalnum() -> bool
Return True if all characters in S are alphanumeric
and there is at least one character in S, False otherwise.
If you insist on using regex, other solutions will do fine. However note that if it can be done without using a regular expression, that's the best way to go about it.
ActiveMQ or RabbitMQ or ZeroMQ or
About ZeroMQ aka 0MQ, as you might already know, it's the one that will get you the most messages per seconds (they were about 4 millions per sec on their ref server last time I checked), but as you might also already know, the documentation is non existent. You will have a hard time finding how to start the server(s), let alone how to use them. I guess that's partly why no one contributed about 0MQ yet.
Have fun!
jQuery UI DatePicker to show year only
In 2018,
$('#datepicker').datepicker({
format: "yyyy",
weekStart: 1,
orientation: "bottom",
language: "{{ app.request.locale }}",
keyboardNavigation: false,
viewMode: "years",
minViewMode: "years"
});
Http post and get request in angular 6
Update :
In angular 7, they are the same as 6
In angular 6
the complete answer found in live example
/** POST: add a new hero to the database */
addHero (hero: Hero): Observable<Hero> {
return this.http.post<Hero>(this.heroesUrl, hero, httpOptions)
.pipe(
catchError(this.handleError('addHero', hero))
);
}
/** GET heroes from the server */
getHeroes (): Observable<Hero[]> {
return this.http.get<Hero[]>(this.heroesUrl)
.pipe(
catchError(this.handleError('getHeroes', []))
);
}
it's because of pipeable/lettable operators
which now angular is able to use tree-shakable
and remove unused imports and optimize the app
some rxjs functions are changed
do -> tap
catch -> catchError
switch -> switchAll
finally -> finalize
more in MIGRATION
and Import paths
For JavaScript developers, the general rule is as follows:
rxjs: Creation methods, types, schedulers and utilities
import { Observable, Subject, asapScheduler, pipe, of, from, interval, merge, fromEvent } from 'rxjs';
rxjs/operators: All pipeable operators:
import { map, filter, scan } from 'rxjs/operators';
rxjs/webSocket: The web socket subject implementation
import { webSocket } from 'rxjs/webSocket';
rxjs/ajax: The Rx ajax implementation
import { ajax } from 'rxjs/ajax';
rxjs/testing: The testing utilities
import { TestScheduler } from 'rxjs/testing';
and for backward compatability you can use rxjs-compat
jquery .html() vs .append()
They are not the same. The first one replaces the HTML without creating another jQuery object first. The second creates an additional jQuery wrapper for the second div, then appends it to the first.
One jQuery Wrapper (per example):
$("#myDiv").html('<div id="mySecondDiv"></div>');
$("#myDiv").append('<div id="mySecondDiv"></div>');
Two jQuery Wrappers (per example):
var mySecondDiv=$('<div id="mySecondDiv"></div>');
$('#myDiv').html(mySecondDiv);
var mySecondDiv=$('<div id="mySecondDiv"></div>');
$('#myDiv').append(mySecondDiv);
You have a few different use cases going on. If you want to replace the content, .html
is a great call since its the equivalent of innerHTML = "..."
. However, if you just want to append content, the extra $()
wrapper set is unneeded.
Only use two wrappers if you need to manipulate the added div
later on. Even in that case, you still might only need to use one:
var mySecondDiv = $("<div id='mySecondDiv'></div>").appendTo("#myDiv");
// other code here
mySecondDiv.hide();
Error ITMS-90717: "Invalid App Store Icon"
Alternative:(Using Sierra or High Sierra and Ionic)
- Copy and Paste the App Store icon to the desktop.
- Open the image. Click File Menu->Duplicate.
- Save it by unticking the Alpha channel.
- Replace the current App Store icon with this one.
- Validate and upload.
How do I execute a stored procedure once for each row returned by query?
Can this not be done with a user-defined function to replicate whatever your stored procedure is doing?
SELECT udfMyFunction(user_id), someOtherField, etc FROM MyTable WHERE WhateverCondition
where udfMyFunction is a function you make that takes in the user ID and does whatever you need to do with it.
See http://www.sqlteam.com/article/user-defined-functions for a bit more background
I agree that cursors really ought to be avoided where possible. And it usually is possible!
(of course, my answer presupposes that you're only interested in getting the output from the SP and that you're not changing the actual data. I find "alters user data in a certain way" a little ambiguous from the original question, so thought I'd offer this as a possible solution. Utterly depends on what you're doing!)
Should a function have only one return statement?
I always avoid multiple return statements. Even in small functions. Small functions can become larger, and tracking the multiple return paths makes it harder (to my small mind) to keep track of what is going on. A single return also makes debugging easier. I've seen people post that the only alternative to multiple return statements is a messy arrow of nested IF statements 10 levels deep. While I certain agree that such coding does occur, it isn't the only option. I wouldn't make the choice between a multiple return statements and a nest of IFs, I'd refactor it so you'd eliminate both. And that is how I code. The following code eliminates both issues and, in my mind, is very easy to read:
public string GetResult()
{
string rv = null;
bool okay = false;
okay = PerformTest(1);
if (okay)
{
okay = PerformTest(2);
}
if (okay)
{
okay = PerformTest(3);
}
if (okay)
{
okay = PerformTest(4);
};
if (okay)
{
okay = PerformTest(5);
}
if (okay)
{
rv = "All Tests Passed";
}
return rv;
}
How to get the last N records in mongodb?
@bin-chen,
You can use an aggregation for the latest n entries of a subset of documents in a collection. Here's a simplified example without grouping (which you would be doing between stages 4 and 5 in this case).
This returns the latest 20 entries (based on a field called "timestamp"), sorted ascending. It then projects each documents _id, timestamp and whatever_field_you_want_to_show into the results.
var pipeline = [
{
"$match": { //stage 1: filter out a subset
"first_field": "needs to have this value",
"second_field": "needs to be this"
}
},
{
"$sort": { //stage 2: sort the remainder last-first
"timestamp": -1
}
},
{
"$limit": 20 //stage 3: keep only 20 of the descending order subset
},
{
"$sort": {
"rt": 1 //stage 4: sort back to ascending order
}
},
{
"$project": { //stage 5: add any fields you want to show in your results
"_id": 1,
"timestamp" : 1,
"whatever_field_you_want_to_show": 1
}
}
]
yourcollection.aggregate(pipeline, function resultCallBack(err, result) {
// account for (err)
// do something with (result)
}
so, result would look something like:
{
"_id" : ObjectId("5ac5b878a1deg18asdafb060"),
"timestamp" : "2018-04-05T05:47:37.045Z",
"whatever_field_you_want_to_show" : -3.46000003814697
}
{
"_id" : ObjectId("5ac5b878a1de1adsweafb05f"),
"timestamp" : "2018-04-05T05:47:38.187Z",
"whatever_field_you_want_to_show" : -4.13000011444092
}
Hope this helps.
Java, How to implement a Shift Cipher (Caesar Cipher)
Two ways to implement a Caesar Cipher:
Option 1:
Change chars to ASCII numbers, then you can increase the value, then revert it back to the new character.
Option 2: Use a Map map each letter to a digit like this.
A - 0
B - 1
C - 2
etc...
With a map you don't have to re-calculate the shift every time. Then you can change to and from plaintext to encrypted by following map.
Angular 2 'component' is not a known element
I know this is a long resolved problem, but in my case I had a different solution.
It was actually a mistake I made that maybe you made as well and didn't fully notice. My mistake was that I accidentally placed a Module e.g., MatChipsModule, MatAutoCompleteModule, on the declarations section; the section that is composed only by components e.g., MainComponent, AboutComponent. This made all my other import unrecognizable.
Where can I find System.Web.Helpers, System.Web.WebPages, and System.Web.Razor?
I had the same problem , first I couldn't find those dlls
in the list of .NET components
. but later I figured it out that the solution is :
1- first I changed target framework
from .NET framework 4 client profile
to .NET framework 4
.
2- then scroll down the list of .NET components
, pass first list of system.web.
.. , scroll down , and find the second list of system.web.
.. at the bottom , they're there .
I hope this could help others
What are the advantages and disadvantages of recursion?
To start:
Pros:
- It is the unique way of implementing a variable number of nested loops (and the only elegant way of implementing a big constant number of nested loops).
Cons:
- Recursive methods will often throw a StackOverflowException when processing big sets. Recursive loops don't have this problem though.
Calling Web API from MVC controller
Its very late here but thought to share below code.
If we have our WebApi as a different project altogether in the same solution then we can call the same from MVC controller like below
public class ProductsController : Controller
{
// GET: Products
public async Task<ActionResult> Index()
{
string apiUrl = "http://localhost:58764/api/values";
using (HttpClient client=new HttpClient())
{
client.BaseAddress = new Uri(apiUrl);
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));
HttpResponseMessage response = await client.GetAsync(apiUrl);
if (response.IsSuccessStatusCode)
{
var data = await response.Content.ReadAsStringAsync();
var table = Newtonsoft.Json.JsonConvert.DeserializeObject<System.Data.DataTable>(data);
}
}
return View();
}
}
Font-awesome, input type 'submit'
With multiple submits, when you need the value of the submit selected, this can be done quite easily. Just create a hidden field in your form and change its value depending on what button is clicked. For example, in the form, say you have:
<input type="hidden" id="Clicked" name="Clicked" value="" />
<button type="submit" class="btn btn-success ClickCheck" id="Create"> <i class="fa fa-file-pdf-o"> Create Bill</i></button>
<button type="submit" class="btn btn-success ClickCheck" id="Reset"> <i class="fa fa-times"> Reset</i></button>
<button type="submit" class="btn btn-success ClickCheck" id="StoreData"> <i class="fa fa-archive"> Save</i></button>
Using jQuery:
<script type="text/javascript">
$(document).ready(function()
{
$('.ClickCheck').click(function()
{
var ButtonID = $(this).attr('id');
$('#Clicked').val(ButtonID);
});
});
</script>
Then you can retrieve the value of the button clicked in the "Clicked" post variable
How to write a simple Java program that finds the greatest common divisor between two numbers?
import java.util.Scanner;
class CalculateGCD
{
public static int calGCD(int a, int b)
{
int c=0,d=0;
if(a>b){c=b;}
else{c=a;}
for(int i=c; i>0; i--)
{
if(((a%i)+(b%i))==0)
{
d=i;
break;
}
}
return d;
}
public static void main(String args[])
{
Scanner sc=new Scanner(System.in);
System.out.println("Enter the nos whose GCD is to be calculated:");
int a=sc.nextInt();
int b=sc.nextInt();
System.out.println(calGCD(a,b));
}
}
'adb' is not recognized as an internal or external command, operable program or batch file
I recommand you using PowerShell
Set Android Studio Terminal to PowerShell:
Settings > Tools > Terminal > Shell path = pwsh.exe (instead of cmd.exe)
Open Terminal on Android Studio
PowerShell 7.0.1
Copyright (c) Microsoft Corporation. All rights reserved.
https://aka.ms/powershell
Type 'help' to get help.
PS >
Test the path for adb.exe
# `pikachu` should be replace your username
PS > test-path "C:\Users\pikachu\AppData\Local\Android\sdk\platform-tools"
True
Open your powershell profile file in your text editor
PS > notepad $profile
add below line, save and exit
# `pikachu` should be replaced with your username
$env:PATH+="C:\Users\pikachu\AppData\Local\Android\sdk\platform-tools"
re-open Terminal and try adb
PS > adb
Android Debug Bridge version 1.0.41
Version 30.0.1-6435776
Installed as C:\Users\hdformat\AppData\Local\Android\sdk\platform-tools\adb.exe
global options:
-a listen on all network interfaces, not just localhost
-d use USB device (error if multiple devices connected)
-e use TCP/IP device (error if multiple TCP/IP devices available)
-s SERIAL use device with given serial (overrides $ANDROID_SERIAL)
-t ID use device with given transport id
-H name of adb server host [default=localhost]
-P port of adb server [default=5037]
How exactly to use Notification.Builder
Notification Builder is strictly for Android API Level 11 and above (Android 3.0 and up).
Hence, if you are not targeting Honeycomb tablets, you should not be using the Notification Builder but rather follow older notification creation methods like the following example.
How do I extract part of a string in t-sql
I would recommend a combination of PatIndex and Left. Carefully constructed, you can write a query that always works, no matter what your data looks like.
Ex:
Declare @Temp Table(Data VarChar(20))
Insert Into @Temp Values('BTA200')
Insert Into @Temp Values('BTA50')
Insert Into @Temp Values('BTA030')
Insert Into @Temp Values('BTA')
Insert Into @Temp Values('123')
Insert Into @Temp Values('X999')
Select Data, Left(Data, PatIndex('%[0-9]%', Data + '1') - 1)
From @Temp
PatIndex will look for the first character that falls in the range of 0-9, and return it's character position, which you can use with the LEFT function to extract the correct data. Note that PatIndex is actually using Data + '1'. This protects us from data where there are no numbers found. If there are no numbers, PatIndex would return 0. In this case, the LEFT function would error because we are using Left(Data, PatIndex - 1). When PatIndex returns 0, we would end up with Left(Data, -1) which returns an error.
There are still ways this can fail. For a full explanation, I encourage you to read:
Extracting numbers with SQL Server
That article shows how to get numbers out of a string. In your case, you want to get alpha characters instead. However, the process is similar enough that you can probably learn something useful out of it.
Import CSV to SQLite
What also is being said in the comments, SQLite sees your input as 1, 25, 62, 7. I also had a problem with , and in my case it was solved by changing "separator ," into ".mode csv". So you could try:
sqlite> create table foo(a, b);
sqlite> .mode csv
sqlite> .import test.csv foo
The first command creates the column names for the table. However, if you want the column names inherited from the csv file, you might just ignore the first line.
Resize UIImage by keeping Aspect ratio and width
If somebody needs this solution in Swift 5:
private func resizeImage(image: UIImage, newHeight: CGFloat) -> UIImage {
let scale = newHeight / image.size.height
let newWidth = image.size.width * scale
UIGraphicsBeginImageContext(CGSize(width:newWidth, height:newHeight))
image.draw(in:CGRect(x:0, y:0, width:newWidth, height:newHeight))
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage
}
Strange Characters in database text: Ã, Ã, ¢, â‚ €,
This is surely an encoding problem. You have a different encoding in your database and in your website and this fact is the cause of the problem. Also if you ran that command you have to change the records that are already in your tables to convert those character in UTF-8.
Update: Based on your last comment, the core of the problem is that you have a database and a data source (the CSV file) which use different encoding. Hence you can convert your database in UTF-8 or, at least, when you get the data that are in the CSV, you have to convert them from UTF-8 to latin1.
You can do the convertion following this articles:
WebSocket connection failed: Error during WebSocket handshake: Unexpected response code: 400
I think you should define your origins
for client side as bellow:
_x000D_
_x000D_
//server.js_x000D_
const socket = require('socket.io');_x000D_
const app = require('express')();_x000D_
const server = app.listen('port');_x000D_
_x000D_
const io = socket().attach(server);_x000D_
io.origins("your_domain:port www.your_domain:port your_IP:port your_domain:*")_x000D_
_x000D_
io.on('connection', (socket) => {_x000D_
console.log('connected a new client');_x000D_
});_x000D_
_x000D_
//client.js_x000D_
var socket = io('ws://:port');
_x000D_
_x000D_
_x000D_
Removing duplicates in the lists
Without using set
data=[1, 2, 3, 1, 2, 5, 6, 7, 8]
uni_data=[]
for dat in data:
if dat not in uni_data:
uni_data.append(dat)
print(uni_data)
Difference between HashSet and HashMap?
Differences between HashSet and HashMap in Java
HashSet internally uses HashMap to store objects.when add(String) method called it calls HahsMap put(key,value) method where key=String object & value=new Object(Dummy).so it maintain no duplicates because keys are nothing but Value Object.
the Objects which are stored as key in Hashset/HashMap should override hashcode & equals contract.
Keys which are used to access/store value objects in HashMap should declared as Final because when it is modified Value object can't be located & returns null.
Error during SSL Handshake with remote server
Faced the same problem as OP:
- Tomcat returned response when accessing directly via SOAP UI
- Didn't load html files
- When used Apache properties mentioned by the previous answer, web-page appeared but AngularJS couldn't get HTTP response
Tomcat SSL certificate was expired while a browser showed it as secure - Apache certificate was far from expiration. Updating Tomcat KeyStore file solved the problem.
How to keep keys/values in same order as declared?
Note that this answer applies to python versions prior to python3.7. CPython 3.6 maintains insertion order under most circumstances as an implementation detail. Starting from Python3.7 onward, it has been declared that implementations MUST maintain insertion order to be compliant.
python dictionaries are unordered. If you want an ordered dictionary, try collections.OrderedDict.
Note that OrderedDict was introduced into the standard library in python 2.7. If you have an older version of python, you can find recipes for ordered dictionaries on ActiveState.
Difference between jar and war in Java
JAR files allow to package multiple files in order to use it as a library, plugin, or any kind of application. On the other hand, WAR files are used only for web applications.
JAR can be created with any desired structure. In contrast, WAR has a predefined structure with WEB-INF and META-INF directories.
A JAR file allows Java Runtime Environment (JRE) to deploy an entire application including the classes and the associated resources in a single request. On the other hand, a WAR file allows testing and deploying a web application easily.
How to set my phpmyadmin user session to not time out so quickly?
To increase the phpMyAdmin
Session Timeout, open config.inc.php
in the root phpMyAdmin
directory and add this setting (anywhere).
$cfg['LoginCookieValidity'] = <your_new_timeout>;
Where <your_new_timeout>
is some number larger than 1800.
Note:
Always keep on mind that a short cookie lifetime is all well and good for the development server. So do not do this on your production server.
How to get list of dates between two dates in mysql select query
Try:
select * from
(select adddate('1970-01-01',t4.i*10000 + t3.i*1000 + t2.i*100 + t1.i*10 + t0.i) selected_date from
(select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t0,
(select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t1,
(select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t2,
(select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t3,
(select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t4) v
where selected_date between '2012-02-10' and '2012-02-15'
-for date ranges up to nearly 300 years in the future.
[Corrected following a suggested edit by UrvishAtSynapse.]
Can I obtain method parameter name using Java reflection?
As @Bozho stated, it is possible to do it if debug information is included during compilation.
There's a good answer here...
How to get the parameter names of an object's constructors (reflection)? by
@AdamPaynter
...using the ASM library. I put together an example showing how you can achieve your goal.
First of all, start with a pom.xml with these dependencies.
<dependency>
<groupId>org.ow2.asm</groupId>
<artifactId>asm-all</artifactId>
<version>5.2</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
Then, this class should do what you want. Just invoke the static method getParameterNames()
.
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.Type;
import org.objectweb.asm.tree.ClassNode;
import org.objectweb.asm.tree.LocalVariableNode;
import org.objectweb.asm.tree.MethodNode;
public class ArgumentReflection {
/**
* Returns a list containing one parameter name for each argument accepted
* by the given constructor. If the class was compiled with debugging
* symbols, the parameter names will match those provided in the Java source
* code. Otherwise, a generic "arg" parameter name is generated ("arg0" for
* the first argument, "arg1" for the second...).
*
* This method relies on the constructor's class loader to locate the
* bytecode resource that defined its class.
*
* @param theMethod
* @return
* @throws IOException
*/
public static List<String> getParameterNames(Method theMethod) throws IOException {
Class<?> declaringClass = theMethod.getDeclaringClass();
ClassLoader declaringClassLoader = declaringClass.getClassLoader();
Type declaringType = Type.getType(declaringClass);
String constructorDescriptor = Type.getMethodDescriptor(theMethod);
String url = declaringType.getInternalName() + ".class";
InputStream classFileInputStream = declaringClassLoader.getResourceAsStream(url);
if (classFileInputStream == null) {
throw new IllegalArgumentException(
"The constructor's class loader cannot find the bytecode that defined the constructor's class (URL: "
+ url + ")");
}
ClassNode classNode;
try {
classNode = new ClassNode();
ClassReader classReader = new ClassReader(classFileInputStream);
classReader.accept(classNode, 0);
} finally {
classFileInputStream.close();
}
@SuppressWarnings("unchecked")
List<MethodNode> methods = classNode.methods;
for (MethodNode method : methods) {
if (method.name.equals(theMethod.getName()) && method.desc.equals(constructorDescriptor)) {
Type[] argumentTypes = Type.getArgumentTypes(method.desc);
List<String> parameterNames = new ArrayList<String>(argumentTypes.length);
@SuppressWarnings("unchecked")
List<LocalVariableNode> localVariables = method.localVariables;
for (int i = 1; i <= argumentTypes.length; i++) {
// The first local variable actually represents the "this"
// object if the method is not static!
parameterNames.add(localVariables.get(i).name);
}
return parameterNames;
}
}
return null;
}
}
Here's an example with a unit test.
public class ArgumentReflectionTest {
@Test
public void shouldExtractTheNamesOfTheParameters3() throws NoSuchMethodException, SecurityException, IOException {
List<String> parameterNames = ArgumentReflection
.getParameterNames(Clazz.class.getMethod("callMe", String.class, String.class));
assertEquals("firstName", parameterNames.get(0));
assertEquals("lastName", parameterNames.get(1));
assertEquals(2, parameterNames.size());
}
public static final class Clazz {
public void callMe(String firstName, String lastName) {
}
}
}
You can find the complete example on GitHub
Caveats
- I slightly changed the original solution from @AdamPaynter to make it work for Methods. If I properly understood, his solution works only with constructors.
- This solution does not work with
static
methods. This is becasue in this case the number of arguments returned by ASM is different, but it something that can be easily fixed.
Maven in Eclipse: step by step installation
(Edit 2016-10-12: Many Eclipse downloads from https://eclipse.org/downloads/eclipse-packages/ have M2Eclipse included already. As of Neon both the Java and the Java EE packages do - look for "Maven support")
Way 1: Maven Eclipse plugin installation step by step:
- Open Eclipse IDE
- Click Help -> Install New Software...
- Click Add button at top right corner
At pop up: fill up Name as "M2Eclipse" and Location as "http://download.eclipse.org/technology/m2e/releases"
or
http://download.eclipse.org/technology/m2e/milestones/1.0
Now click OK
After that installation would be started.
Way 2: Another way to install Maven plug-in for Eclipse by "Eclipse Marketplace":
- Open Eclipse
- Go to Help -> Eclipse Marketplace
- Search by Maven
- Click "Install" button at "Maven Integration for Eclipse" section
- Follow the instruction step by step
After successful installation do the followings in Eclipse:
- Go to Window --> Preferences
- Observe, Maven is enlisted at left panel
Finally,
- Click on an existing project
- Select Configure -> Convert to Maven Project
How to create a file in Android?
I decided to write a class from this thread that may be helpful to others. Note that this is currently intended to write in the "files" directory only (e.g. does not write to "sdcard" paths).
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import android.content.Context;
public class AndroidFileFunctions {
public static String getFileValue(String fileName, Context context) {
try {
StringBuffer outStringBuf = new StringBuffer();
String inputLine = "";
/*
* We have to use the openFileInput()-method the ActivityContext
* provides. Again for security reasons with openFileInput(...)
*/
FileInputStream fIn = context.openFileInput(fileName);
InputStreamReader isr = new InputStreamReader(fIn);
BufferedReader inBuff = new BufferedReader(isr);
while ((inputLine = inBuff.readLine()) != null) {
outStringBuf.append(inputLine);
outStringBuf.append("\n");
}
inBuff.close();
return outStringBuf.toString();
} catch (IOException e) {
return null;
}
}
public static boolean appendFileValue(String fileName, String value,
Context context) {
return writeToFile(fileName, value, context, Context.MODE_APPEND);
}
public static boolean setFileValue(String fileName, String value,
Context context) {
return writeToFile(fileName, value, context,
Context.MODE_WORLD_READABLE);
}
public static boolean writeToFile(String fileName, String value,
Context context, int writeOrAppendMode) {
// just make sure it's one of the modes we support
if (writeOrAppendMode != Context.MODE_WORLD_READABLE
&& writeOrAppendMode != Context.MODE_WORLD_WRITEABLE
&& writeOrAppendMode != Context.MODE_APPEND) {
return false;
}
try {
/*
* We have to use the openFileOutput()-method the ActivityContext
* provides, to protect your file from others and This is done for
* security-reasons. We chose MODE_WORLD_READABLE, because we have
* nothing to hide in our file
*/
FileOutputStream fOut = context.openFileOutput(fileName,
writeOrAppendMode);
OutputStreamWriter osw = new OutputStreamWriter(fOut);
// Write the string to the file
osw.write(value);
// save and close
osw.flush();
osw.close();
} catch (IOException e) {
return false;
}
return true;
}
public static void deleteFile(String fileName, Context context) {
context.deleteFile(fileName);
}
}
Download file from web in Python 3
I hope I understood the question right, which is: how to download a file from a server when the URL is stored in a string type?
I download files and save it locally using the below code:
import requests
url = 'https://www.python.org/static/img/python-logo.png'
fileName = 'D:\Python\dwnldPythonLogo.png'
req = requests.get(url)
file = open(fileName, 'wb')
for chunk in req.iter_content(100000):
file.write(chunk)
file.close()
Exception is never thrown in body of corresponding try statement
As pointed out in the comments, you cannot catch an exception that's not thrown by the code within your try
block. Try changing your code to:
try{
Integer.parseInt(args[i-1]); // this only throws a NumberFormatException
}
catch(NumberFormatException e){
throw new MojException("Bledne dane");
}
Always check the documentation to see what exceptions are thrown by each method. You may also wish to read up on the subject of checked vs unchecked exceptions before that causes you any confusion in the future.
Debugging in Maven?
Why not use the JPDA and attach to the launched process from a separate debugger process ? You should be able to specify the appropriate options in Maven to launch your process with the debugging hooks enabled. This article has more information.
How to extract 1 screenshot for a video with ffmpeg at a given time?
FFMpeg can do this by seeking to the given timestamp and extracting exactly one frame as an image, see for instance:
ffmpeg -i input_file.mp4 -ss 01:23:45 -vframes 1 output.jpg
Let's explain the options:
-i input file the path to the input file
-ss 01:23:45 seek the position to the specified timestamp
-vframes 1 only handle one video frame
output.jpg output filename, should have a well-known extension
The -ss
parameter accepts a value in the form HH:MM:SS[.xxx]
or as a number in seconds. If you need a percentage, you need to compute the video duration beforehand.
Best way to call a JSON WebService from a .NET Console
WebClient to fetch the contents from the remote url and JavaScriptSerializer or Json.NET to deserialize the JSON into a .NET object. For example you define a model class which will reflect the JSON structure and then:
using (var client = new WebClient())
{
var json = client.DownloadString("http://example.com/json");
var serializer = new JavaScriptSerializer();
SomeModel model = serializer.Deserialize<SomeModel>(json);
// TODO: do something with the model
}
There are also some REST client frameworks you may checkout such as RestSharp.
How can I fill a column with random numbers in SQL? I get the same value in every row
require_once('db/connect.php');
//rand(1000000 , 9999999);
$products_query = "SELECT id FROM products";
$products_result = mysqli_query($conn, $products_query);
$products_row = mysqli_fetch_array($products_result);
$ids_array = [];
do
{
array_push($ids_array, $products_row['id']);
}
while($products_row = mysqli_fetch_array($products_result));
/*
echo '<pre>';
print_r($ids_array);
echo '</pre>';
*/
$row_counter = count($ids_array);
for ($i=0; $i < $row_counter; $i++)
{
$current_row = $ids_array[$i];
$rand = rand(1000000 , 9999999);
mysqli_query($conn , "UPDATE products SET code='$rand' WHERE id='$current_row'");
}
How to remove all duplicate items from a list
No, it's simply a typo, the "list" at the end must be capitalized. You can nest loops over the same variable just fine (although there's rarely a good reason to).
However, there are other problems with the code. For starters, you're iterating through lists, so i
and j
will be items not indices. Furthermore, you can't change a collection while iterating over it (well, you "can" in that it runs, but madness lies that way - for instance, you'll propably skip over items). And then there's the complexity problem, your code is O(n^2). Either convert the list into a set
and back into a list
(simple, but shuffles the remaining list items) or do something like this:
seen = set()
new_x = []
for x in xs:
if x in seen:
continue
seen.add(x)
new_xs.append(x)
Both solutions require the items to be hashable. If that's not possible, you'll probably have to stick with your current approach sans the mentioned problems.
'react-scripts' is not recognized as an internal or external command
react-scripts is not recognized as an internal or external command is related to npm.
I would update all of my dependencies in my package.json files to the latest versions in both the main directory and client directory if applicable.
You can do this by using an asterisk "*" instead of specifying a specific version number in your package.json files for your dependencies.
For Example:
"dependencies": {
"body-parser": "*",
"express": "*",
"mongoose": "*",
"react": "*",
"react-dom": "*",
"react-final-form": "*",
"react-final-form-listeners": "*",
"react-mapbox-gl": "*",
"react-redux": "*",
"react-responsive-modal": "*",
}
I would then make sure any package-lock.json were deleted and then run npm install and yarn install in both the main directory and the client directory as well if applicable.
You should then be able to run a yarn build and then use yarn start to run the application.
How to solve "Connection reset by peer: socket write error"?
I've got the same exception and in my case the problem was in a renegotiation procecess. In fact my client closed a connection when the server tried to change a cipher suite. After digging it appears that in the jdk 1.6 update 22 renegotiation process is disabled by default. If your security constraints can effort this, try to enable the unsecure renegotiation by setting the sun.security.ssl.allowUnsafeRenegotiation
system property to true
. Here is some information about the process:
Session renegotiation is a mechanism within the SSL protocol that
allows the client or the server to trigger a new SSL handshake during
an ongoing SSL communication. Renegotiation was initially designed as
a mechanism to increase the security of an ongoing SSL channel, by
triggering the renewal of the crypto keys used to secure that channel.
However, this security measure isn't needed with modern cryptographic
algorithms. Additionally, renegotiation can be used by a server to
request a client certificate (in order to perform client
authentication) when the client tries to access specific, protected
resources on the server.
Additionally there is the excellent post about this issue in details and written in (IMHO) understandable language.
.NET - Get protocol, host, and port
Well if you are doing this in Asp.Net or have access to HttpContext.Current.Request
I'd say these are easier and more general ways of getting them:
var scheme = Request.Url.Scheme; // will get http, https, etc.
var host = Request.Url.Host; // will get www.mywebsite.com
var port = Request.Url.Port; // will get the port
var path = Request.Url.AbsolutePath; // should get the /pages/page1.aspx part, can't remember if it only get pages/page1.aspx
I hope this helps. :)
HttpServletRequest get JSON POST data
Normaly you can GET and POST parameters in a servlet the same way:
request.getParameter("cmd");
But only if the POST data is encoded as key-value pairs of content type: "application/x-www-form-urlencoded" like when you use a standard HTML form.
If you use a different encoding schema for your post data, as in your case when you post a json data stream, you need to use a custom decoder that can process the raw datastream from:
BufferedReader reader = request.getReader();
Json post processing example (uses org.json package )
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
StringBuffer jb = new StringBuffer();
String line = null;
try {
BufferedReader reader = request.getReader();
while ((line = reader.readLine()) != null)
jb.append(line);
} catch (Exception e) { /*report an error*/ }
try {
JSONObject jsonObject = HTTP.toJSONObject(jb.toString());
} catch (JSONException e) {
// crash and burn
throw new IOException("Error parsing JSON request string");
}
// Work with the data using methods like...
// int someInt = jsonObject.getInt("intParamName");
// String someString = jsonObject.getString("stringParamName");
// JSONObject nestedObj = jsonObject.getJSONObject("nestedObjName");
// JSONArray arr = jsonObject.getJSONArray("arrayParamName");
// etc...
}
Best TCP port number range for internal applications
I decided to download the assigned port numbers from IANA, filter out the used ports, and sort each "Unassigned" range in order of most ports available, descending. This did not work, since the csv file has ranges marked as "Unassigned" that overlap other port number reservations. I manually expanded the ranges of assigned port numbers, leaving me with a list of all assigned port numbers. I then sorted that list and generated my own list of unassigned ranges.
Since this stackoverflow.com page ranked very high in my search about the topic, I figured I'd post the largest ranges here for anyone else who is interested. These are for both TCP and UDP where the number of ports in the range is at least 500.
Total Start End
829 29170 29998
815 38866 39680
710 41798 42507
681 43442 44122
661 46337 46997
643 35358 36000
609 36866 37474
596 38204 38799
592 33657 34248
571 30261 30831
563 41231 41793
542 21011 21552
528 28590 29117
521 14415 14935
510 26490 26999
Source (via the CSV download button):
http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml
How to execute a shell script from C in Linux?
If you're ok with POSIX, you can also use popen()
/pclose()
#include <stdio.h>
#include <stdlib.h>
int main(void) {
/* ls -al | grep '^d' */
FILE *pp;
pp = popen("ls -al", "r");
if (pp != NULL) {
while (1) {
char *line;
char buf[1000];
line = fgets(buf, sizeof buf, pp);
if (line == NULL) break;
if (line[0] == 'd') printf("%s", line); /* line includes '\n' */
}
pclose(pp);
}
return 0;
}
PHP script to loop through all of the files in a directory?
If you don't have access to DirectoryIterator class try this:
<?php
$path = "/path/to/files";
if ($handle = opendir($path)) {
while (false !== ($file = readdir($handle))) {
if ('.' === $file) continue;
if ('..' === $file) continue;
// do something with the file
}
closedir($handle);
}
?>
Accessing an array out of bounds gives no error, why?
when you declare int array[2]; you reserve 2 memory spaces of 4 bytes each(32bit program).
if you type array[4] in your code it still corresponds to a valid call but only at run time will it throw an unhandled exception. C++ uses manual memory management. This is actually a security flaw that was used for hacking programs
this can help understanding:
int * somepointer;
somepointer[0]=somepointer[5];
Twitter Bootstrap Modal Form Submit
Simple
<div class="modal-footer">
<button class="btn" data-dismiss="modal" aria-hidden="true">Close</button>
<button class="btn btn-primary" onclick="event.preventDefault();document.getElementById('your-form').submit();">Save changes</button>
Pandas Merge - How to avoid duplicating columns
can't you just subset the columns in either df first?
[i for i in df.columns if i not in df2.columns]
dfNew = merge(df **[i for i in df.columns if i not in df2.columns]**, df2, left_index=True, right_index=True, how='outer')
Message "Async callback was not invoked within the 5000 ms timeout specified by jest.setTimeout"
For Jest 24.9+
we just need to add --testTimeout in the command line
--testTimeout= 10000 // timeout of 10s
The default timeout value is 5000.
This will be applicable for all test cases.
or if you want to give timeout to particular function only then you can use this syntax while declaring the test case.
test(name, fn, timeout)
example
test('example', async () => {
}, 10000); // timeout of 10s (default is 5000)
Where can I set environment variables that crontab will use?
Unfortunately, crontabs have a very limited environment variables scope, thus you need to export them every time the corntab runs.
An easy approach would be the following example, suppose you've your env vars in a file called env, then:
* * * * * . ./env && /path/to_your/command
this part . ./env
will export them and then they're used within the same scope of your command
How to layout multiple panels on a jFrame? (java)
You'll want to use a number of layout managers to help you achieve the basic results you want.
Check out A Visual Guide to Layout Managers for a comparision.
You could use a GridBagLayout
but that's one of the most complex (and powerful) layout managers available in the JDK.
You could use a series of compound layout managers instead.
I'd place the graphics component and text area on a single JPanel
, using a BorderLayout
, with the graphics component in the CENTER
and the text area in the SOUTH
position.
I'd place the text field and button on a separate JPanel
using a GridBagLayout
(because it's the simplest I can think of to achieve the over result you want)
I'd place these two panels onto a third, master, panel, using a BorderLayout
, with the first panel in the CENTER
and the second at the SOUTH
position.
But that's me
Text vertical alignment in WPF TextBlock
If you can overlook the height of TextBlock, it's better for you to use this:
<TextBlock Height="{Binding}" Text="Your text"
TextWrapping="Wrap" VerticalAlignment="Center" Width="28"/>
How to NodeJS require inside TypeScript file?
Typescript will always complain when it is unable to find a symbol. The compiler comes together with a set of default definitions for window
, document
and such specified in a file called lib.d.ts
. If I do a grep for require
in this file I can find no definition of a function require
. Hence, we have to tell the compiler ourselves that this function will exist at runtime using the declare
syntax:
declare function require(name:string);
var sampleModule = require('modulename');
On my system, this compiles just fine.
Calculating Page Table Size
Since we have a virtual address space of 2^32 and each page size is 2^12, we can store (2^32/2^12) = 2^20 pages. Since each entry into this page table has an address of size 4 bytes, then we have 2^20*4 = 4MB. So the page table takes up 4MB in memory.
E: Unable to locate package npm
Encountered this in Ubuntu for Windows, try running first
sudo apt-get update
sudo apt-get upgrade
then
sudo apt-get install npm
How to debug JavaScript / jQuery event bindings with Firebug or similar tools?
There's a nice bookmarklet called Visual Event that can show you all the events attached to an element. It has color-coded highlights for different types of events (mouse, keyboard, etc.). When you hover over them, it shows the body of the event handler, how it was attached, and the file/line number (on WebKit and Opera). You can also trigger the event manually.
It can't find every event because there's no standard way to look up what event handlers are attached to an element, but it works with popular libraries like jQuery, Prototype, MooTools, YUI, etc.
Drop a temporary table if it exists
What you asked for is:
IF OBJECT_ID('tempdb..##CLIENTS_KEYWORD') IS NOT NULL
BEGIN
DROP TABLE ##CLIENTS_KEYWORD
CREATE TABLE ##CLIENTS_KEYWORD(client_id int)
END
ELSE
CREATE TABLE ##CLIENTS_KEYWORD(client_id int)
IF OBJECT_ID('tempdb..##TEMP_CLIENTS_KEYWORD') IS NOT NULL
BEGIN
DROP TABLE ##TEMP_CLIENTS_KEYWORD
CREATE TABLE ##TEMP_CLIENTS_KEYWORD(client_id int)
END
ELSE
CREATE TABLE ##TEMP_CLIENTS_KEYWORD(client_id int)
Since you're always going to create the table, regardless of whether the table is deleted or not; a slightly optimised solution is:
IF OBJECT_ID('tempdb..##CLIENTS_KEYWORD') IS NOT NULL
DROP TABLE ##CLIENTS_KEYWORD
CREATE TABLE ##CLIENTS_KEYWORD(client_id int)
IF OBJECT_ID('tempdb..##TEMP_CLIENTS_KEYWORD') IS NOT NULL
DROP TABLE ##TEMP_CLIENTS_KEYWORD
CREATE TABLE ##TEMP_CLIENTS_KEYWORD(client_id int)
Difference between filter and filter_by in SQLAlchemy
filter_by
is used for simple queries on the column names using regular kwargs, like
db.users.filter_by(name='Joe')
The same can be accomplished with filter
, not using kwargs, but instead using the '==' equality operator, which has been overloaded on the db.users.name object:
db.users.filter(db.users.name=='Joe')
You can also write more powerful queries using filter
, such as expressions like:
db.users.filter(or_(db.users.name=='Ryan', db.users.country=='England'))
How to programmatically set the Image source
Use asp:image
<asp:Image id="Image1" runat="server"
AlternateText="Image text"
ImageAlign="left"
ImageUrl="images/image1.jpg"/>
and codebehind to change image url
Image1.ImageUrl = "/MyProject;component/Images/down.png";
Pass a data.frame column name to a function
This answer will cover many of the same elements as existing answers, but this issue (passing column names to functions) comes up often enough that I wanted there to be an answer that covered things a little more comprehensively.
Suppose we have a very simple data frame:
dat <- data.frame(x = 1:4,
y = 5:8)
and we'd like to write a function that creates a new column z
that is the sum of columns x
and y
.
A very common stumbling block here is that a natural (but incorrect) attempt often looks like this:
foo <- function(df,col_name,col1,col2){
df$col_name <- df$col1 + df$col2
df
}
#Call foo() like this:
foo(dat,z,x,y)
The problem here is that df$col1
doesn't evaluate the expression col1
. It simply looks for a column in df
literally called col1
. This behavior is described in ?Extract
under the section "Recursive (list-like) Objects".
The simplest, and most often recommended solution is simply switch from $
to [[
and pass the function arguments as strings:
new_column1 <- function(df,col_name,col1,col2){
#Create new column col_name as sum of col1 and col2
df[[col_name]] <- df[[col1]] + df[[col2]]
df
}
> new_column1(dat,"z","x","y")
x y z
1 1 5 6
2 2 6 8
3 3 7 10
4 4 8 12
This is often considered "best practice" since it is the method that is hardest to screw up. Passing the column names as strings is about as unambiguous as you can get.
The following two options are more advanced. Many popular packages make use of these kinds of techniques, but using them well requires more care and skill, as they can introduce subtle complexities and unanticipated points of failure. This section of Hadley's Advanced R book is an excellent reference for some of these issues.
If you really want to save the user from typing all those quotes, one option might be to convert bare, unquoted column names to strings using deparse(substitute())
:
new_column2 <- function(df,col_name,col1,col2){
col_name <- deparse(substitute(col_name))
col1 <- deparse(substitute(col1))
col2 <- deparse(substitute(col2))
df[[col_name]] <- df[[col1]] + df[[col2]]
df
}
> new_column2(dat,z,x,y)
x y z
1 1 5 6
2 2 6 8
3 3 7 10
4 4 8 12
This is, frankly, a bit silly probably, since we're really doing the same thing as in new_column1
, just with a bunch of extra work to convert bare names to strings.
Finally, if we want to get really fancy, we might decide that rather than passing in the names of two columns to add, we'd like to be more flexible and allow for other combinations of two variables. In that case we'd likely resort to using eval()
on an expression involving the two columns:
new_column3 <- function(df,col_name,expr){
col_name <- deparse(substitute(col_name))
df[[col_name]] <- eval(substitute(expr),df,parent.frame())
df
}
Just for fun, I'm still using deparse(substitute())
for the name of the new column. Here, all of the following will work:
> new_column3(dat,z,x+y)
x y z
1 1 5 6
2 2 6 8
3 3 7 10
4 4 8 12
> new_column3(dat,z,x-y)
x y z
1 1 5 -4
2 2 6 -4
3 3 7 -4
4 4 8 -4
> new_column3(dat,z,x*y)
x y z
1 1 5 5
2 2 6 12
3 3 7 21
4 4 8 32
So the short answer is basically: pass data.frame column names as strings and use [[
to select single columns. Only start delving into eval
, substitute
, etc. if you really know what you're doing.
Preserve Line Breaks From TextArea When Writing To MySQL
Here is what I use
$textToStore = nl2br(htmlentities($inputText, ENT_QUOTES, 'UTF-8'));
$inputText
is the text provided by either the form or textarea.
$textToStore
is the returned text from nl2br
and htmlentities
, to be stored in your database.
ENT_QUOTES
will convert both double and single quotes, so you'll have no trouble with those.
Check whether an input string contains a number in javascript
One way to check it is to loop through the string and return true (or false depending on what you want) when you hit a number.
function checkStringForNumbers(input){
let str = String(input);
for( let i = 0; i < str.length; i++){
console.log(str.charAt(i));
if(!isNaN(str.charAt(i))){ //if the string is a number, do the following
return true;
}
}
}
What do .c and .h file extensions mean to C?
They're not really library files. They're just source files. Like Stefano said, the .c file is the C source file which actually uses/defines the actual source of what it merely outlined in the .h file, the header file. The header file usually outlines all of the function prototypes and structures that will be used in the actual source file. Think of it like a reference/appendix. This is evident upon looking at the header file, as you will see :) So then when you want to use something that was written in these source files, you #include
the header file, which contains the information that the compiler will need to know.
Detect If Browser Tab Has Focus
Cross Browser jQuery Solution! Raw available at GitHub
Fun & Easy to Use!
The following plugin will go through your standard test for various versions of IE, Chrome, Firefox, Safari, etc.. and establish your declared methods accordingly. It also deals with issues such as:
- onblur|.blur/onfocus|.focus "duplicate" calls
- window losing focus through selection of alternate app, like word
- This tends to be undesirable simply because, if you have a bank page open, and it's onblur event tells it to mask the page, then if you open calculator, you can't see the page anymore!
- Not triggering on page load
Use is as simple as: Scroll Down to 'Run Snippet'
$.winFocus(function(event, isVisible) {
console.log("Combo\t\t", event, isVisible);
});
// OR Pass False boolean, and it will not trigger on load,
// Instead, it will first trigger on first blur of current tab_window
$.winFocus(function(event, isVisible) {
console.log("Combo\t\t", event, isVisible);
}, false);
// OR Establish an object having methods "blur" & "focus", and/or "blurFocus"
// (yes, you can set all 3, tho blurFocus is the only one with an 'isVisible' param)
$.winFocus({
blur: function(event) {
console.log("Blur\t\t", event);
},
focus: function(event) {
console.log("Focus\t\t", event);
}
});
// OR First method becoms a "blur", second method becoms "focus"!
$.winFocus(function(event) {
console.log("Blur\t\t", event);
},
function(event) {
console.log("Focus\t\t", event);
});
_x000D_
_x000D_
/* Begin Plugin */_x000D_
;;(function($){$.winFocus||($.extend({winFocus:function(){var a=!0,b=[];$(document).data("winFocus")||$(document).data("winFocus",$.winFocus.init());for(x in arguments)"object"==typeof arguments[x]?(arguments[x].blur&&$.winFocus.methods.blur.push(arguments[x].blur),arguments[x].focus&&$.winFocus.methods.focus.push(arguments[x].focus),arguments[x].blurFocus&&$.winFocus.methods.blurFocus.push(arguments[x].blurFocus),arguments[x].initRun&&(a=arguments[x].initRun)):"function"==typeof arguments[x]?b.push(arguments[x]):_x000D_
"boolean"==typeof arguments[x]&&(a=arguments[x]);b&&(1==b.length?$.winFocus.methods.blurFocus.push(b[0]):($.winFocus.methods.blur.push(b[0]),$.winFocus.methods.focus.push(b[1])));if(a)$.winFocus.methods.onChange()}}),$.winFocus.init=function(){$.winFocus.props.hidden in document?document.addEventListener("visibilitychange",$.winFocus.methods.onChange):($.winFocus.props.hidden="mozHidden")in document?document.addEventListener("mozvisibilitychange",$.winFocus.methods.onChange):($.winFocus.props.hidden=_x000D_
"webkitHidden")in document?document.addEventListener("webkitvisibilitychange",$.winFocus.methods.onChange):($.winFocus.props.hidden="msHidden")in document?document.addEventListener("msvisibilitychange",$.winFocus.methods.onChange):($.winFocus.props.hidden="onfocusin")in document?document.onfocusin=document.onfocusout=$.winFocus.methods.onChange:window.onpageshow=window.onpagehide=window.onfocus=window.onblur=$.winFocus.methods.onChange;return $.winFocus},$.winFocus.methods={blurFocus:[],blur:[],focus:[],_x000D_
exeCB:function(a){$.winFocus.methods.blurFocus&&$.each($.winFocus.methods.blurFocus,function(b,c){this.apply($.winFocus,[a,!a.hidden])});a.hidden&&$.winFocus.methods.blur&&$.each($.winFocus.methods.blur,function(b,c){this.apply($.winFocus,[a])});!a.hidden&&$.winFocus.methods.focus&&$.each($.winFocus.methods.focus,function(b,c){this.apply($.winFocus,[a])})},onChange:function(a){var b={focus:!1,focusin:!1,pageshow:!1,blur:!0,focusout:!0,pagehide:!0};if(a=a||window.event)a.hidden=a.type in b?b[a.type]:_x000D_
document[$.winFocus.props.hidden],$(window).data("visible",!a.hidden),$.winFocus.methods.exeCB(a);else try{$.winFocus.methods.onChange.call(document,new Event("visibilitychange"))}catch(c){}}},$.winFocus.props={hidden:"hidden"})})(jQuery);_x000D_
/* End Plugin */_x000D_
_x000D_
// Simple example_x000D_
$(function() {_x000D_
$.winFocus(function(event, isVisible) {_x000D_
$('td tbody').empty();_x000D_
$.each(event, function(i) {_x000D_
$('td tbody').append(_x000D_
$('<tr />').append(_x000D_
$('<th />', { text: i }),_x000D_
$('<td />', { text: this.toString() })_x000D_
)_x000D_
)_x000D_
});_x000D_
if (isVisible) _x000D_
$("#isVisible").stop().delay(100).fadeOut('fast', function(e) {_x000D_
$('body').addClass('visible');_x000D_
$(this).stop().text('TRUE').fadeIn('slow');_x000D_
});_x000D_
else {_x000D_
$('body').removeClass('visible');_x000D_
$("#isVisible").text('FALSE');_x000D_
}_x000D_
});_x000D_
})
_x000D_
body { background: #AAF; }_x000D_
table { width: 100%; }_x000D_
table table { border-collapse: collapse; margin: 0 auto; width: auto; }_x000D_
tbody > tr > th { text-align: right; }_x000D_
td { width: 50%; }_x000D_
th, td { padding: .1em .5em; }_x000D_
td th, td td { border: 1px solid; }_x000D_
.visible { background: #FFA; }
_x000D_
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>_x000D_
<h3>See Console for Event Object Returned</h3>_x000D_
<table>_x000D_
<tr>_x000D_
<th><p>Is Visible?</p></th>_x000D_
<td><p id="isVisible">TRUE</p></td>_x000D_
</tr>_x000D_
<tr>_x000D_
<td colspan="2">_x000D_
<table>_x000D_
<thead>_x000D_
<tr>_x000D_
<th colspan="2">Event Data <span style="font-size: .8em;">{ See Console for More Details }</span></th>_x000D_
</tr>_x000D_
</thead>_x000D_
<tbody></tbody>_x000D_
</table>_x000D_
</td>_x000D_
</tr>_x000D_
</table>
_x000D_
_x000D_
_x000D_
How to write a test which expects an Error to be thrown in Jasmine?
Try using an anonymous function instead:
expect( function(){ parser.parse(raw); } ).toThrow(new Error("Parsing is not possible"));
you should be passing a function into the expect(...)
call. Your incorrect code:
// incorrect:
expect(parser.parse(raw)).toThrow(new Error("Parsing is not possible"));
is trying to actually call parser.parse(raw)
in an attempt to pass the result into expect(...)
,
Node.js fs.readdir recursive directory search
If you want to use an npm package, wrench is pretty good.
var wrench = require("wrench");
var files = wrench.readdirSyncRecursive("directory");
wrench.readdirRecursive("directory", function (error, files) {
// live your dreams
});
EDIT (2018):
Anyone reading through in recent time: The author deprecated this package in 2015:
wrench.js is deprecated, and hasn't been updated in quite some time. I heavily recommend using fs-extra to do any extra filesystem operations.
Add IIS 7 AppPool Identities as SQL Server Logons
I figured it out through trial and error... the real chink in the armor was a little known setting in IIS in the Configuration Editor
for the website in
Section: system.webServer/security/authentication/windowsAuthentication
From: ApplicationHost.config <locationpath='ServerName/SiteName' />
called useAppPoolCredentials
(which is set to False
by default. Set this to True
and life becomes great again!!! Hope this saves pain for the next guy....
How to get the dimensions of a tensor (in TensorFlow) at graph construction time?
Just print out the embed after construction graph (ops) without running:
import tensorflow as tf
...
train_dataset = tf.placeholder(tf.int32, shape=[128, 2])
embeddings = tf.Variable(
tf.random_uniform([50000, 64], -1.0, 1.0))
embed = tf.nn.embedding_lookup(embeddings, train_dataset)
print (embed)
This will show the shape of the embed tensor:
Tensor("embedding_lookup:0", shape=(128, 2, 64), dtype=float32)
Usually, it's good to check shapes of all tensors before training your models.
plot legends without border and with white background
Use option bty = "n"
in legend
to remove the box around the legend. For example:
legend(1, 5,
"This legend text should not be disturbed by the dotted grey lines,\nbut the plotted dots should still be visible",
bty = "n")
Unable to verify leaf signature
Another approach to solving this securely is to use the following module.
node_extra_ca_certs_mozilla_bundle
This module can work without any code modification by generating a PEM file that includes all root and intermediate certificates trusted by Mozilla. You can use the following environment variable (Works with Nodejs v7.3+),
NODE_EXTRA_CA_CERTS
To generate the PEM file to use with the above environment variable. You can install the module using:
npm install --save node_extra_ca_certs_mozilla_bundle
and then launch your node script with an environment variable.
NODE_EXTRA_CA_CERTS=node_modules/node_extra_ca_certs_mozilla_bundle/ca_bundle/ca_intermediate_root_bundle.pem node your_script.js
Other ways to use the generated PEM file are available at:
https://github.com/arvind-agarwal/node_extra_ca_certs_mozilla_bundle
NOTE: I am the author of the above module.
SFTP file transfer using Java JSch
Below code works for me
public static void sftpsript(String filepath) {
try {
String user ="demouser"; // username for remote host
String password ="demo123"; // password of the remote host
String host = "demo.net"; // remote host address
JSch jsch = new JSch();
Session session = jsch.getSession(user, host);
session.setPassword(password);
session.connect();
ChannelSftp sftpChannel = (ChannelSftp) session.openChannel("sftp");
sftpChannel.connect();
sftpChannel.put("I:/demo/myOutFile.txt", "/tmp/QA_Auto/myOutFile.zip");
sftpChannel.disconnect();
session.disconnect();
}catch(Exception ex){
ex.printStackTrace();
}
}
OR using StrictHostKeyChecking as "NO" (security consequences)
public static void sftpsript(String filepath) {
try {
String user ="demouser"; // username for remote host
String password ="demo123"; // password of the remote host
String host = "demo.net"; // remote host address
JSch jsch = new JSch();
Session session = jsch.getSession(user, host, 22);
Properties config = new Properties();
config.put("StrictHostKeyChecking", "no");
session.setConfig(config);;
session.setPassword(password);
System.out.println("user=="+user+"\n host=="+host);
session.connect();
ChannelSftp sftpChannel = (ChannelSftp) session.openChannel("sftp");
sftpChannel.connect();
sftpChannel.put("I:/demo/myOutFile.txt", "/tmp/QA_Auto/myOutFile.zip");
sftpChannel.disconnect();
session.disconnect();
}catch(Exception ex){
ex.printStackTrace();
}
}
How to parse month full form string using DateFormat in Java?
LocalDate from java.time
Use LocalDate
from java.time, the modern Java date and time API, for a date
DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern("MMMM d, u", Locale.ENGLISH);
LocalDate date = LocalDate.parse("June 27, 2007", dateFormatter);
System.out.println(date);
Output:
2007-06-27
As others have said already, remember to specify an English-speaking locale when your string is in English. A LocalDate
is a date without time of day, so a lot better suitable for the date from your string than the old Date
class. Despite its name a Date
does not represent a date but a point in time that falls on at least two different dates in different time zones of the world.
Only if you need an old-fashioned Date
for an API that you cannot afford to upgrade to java.time just now, convert like this:
Instant startOfDay = date.atStartOfDay(ZoneId.systemDefault()).toInstant();
Date oldfashionedDate = Date.from(startOfDay);
System.out.println(oldfashionedDate);
Output in my time zone:
Wed Jun 27 00:00:00 CEST 2007
Link
Oracle tutorial: Date Time explaining how to use java.time.
How to empty a list in C#?
Option #1: Use Clear() function to empty the List<T>
and retain it's capacity.
Count is set to 0, and references to other objects from elements of
the collection are also released.
Capacity remains unchanged.
Option #2 - Use Clear() and TrimExcess() functions to set List<T>
to initial state.
Count is set to 0, and references to other objects from elements of
the collection are also released.
Trimming an empty List<T>
sets the capacity of the List to the
default capacity.
Definitions
Count = number of elements that are actually in the List<T>
Capacity = total number of elements the internal data structure can hold without resizing.
Clear() Only
List<string> dinosaurs = new List<string>();
dinosaurs.Add("Compsognathus");
dinosaurs.Add("Amargasaurus");
dinosaurs.Add("Deinonychus");
Console.WriteLine("Count: {0}", dinosaurs.Count);
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
dinosaurs.Clear();
Console.WriteLine("\nClear()");
Console.WriteLine("\nCount: {0}", dinosaurs.Count);
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
Clear() and TrimExcess()
List<string> dinosaurs = new List<string>();
dinosaurs.Add("Triceratops");
dinosaurs.Add("Stegosaurus");
Console.WriteLine("Count: {0}", dinosaurs.Count);
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
dinosaurs.Clear();
dinosaurs.TrimExcess();
Console.WriteLine("\nClear() and TrimExcess()");
Console.WriteLine("\nCount: {0}", dinosaurs.Count);
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
Posting JSON Data to ASP.NET MVC
BeRecursive's answer is the one I used, so that we could standardize on Json.Net (we have MVC5 and WebApi 5 -- WebApi 5 already uses Json.Net), but I found an issue. When you have parameters in your route to which you're POSTing, MVC tries to call the model binder for the URI values, and this code will attempt to bind the posted JSON to those values.
Example:
[HttpPost]
[Route("Customer/{customerId:int}/Vehicle/{vehicleId:int}/Policy/Create"]
public async Task<JsonNetResult> Create(int customerId, int vehicleId, PolicyRequest policyRequest)
The BindModel
function gets called three times, bombing on the first, as it tries to bind the JSON to customerId
with the error: Error reading integer. Unexpected token: StartObject. Path '', line 1, position 1.
I added this block of code to the top of BindModel
:
if (bindingContext.ValueProvider.GetValue(bindingContext.ModelName) != null) {
return base.BindModel(controllerContext, bindingContext);
}
The ValueProvider, fortunately, has route values figured out by the time it gets to this method.
Which is more efficient, a for-each loop, or an iterator?
foreach
uses iterators under the hood anyway. It really is just syntactic sugar.
Consider the following program:
import java.util.List;
import java.util.ArrayList;
public class Whatever {
private final List<Integer> list = new ArrayList<>();
public void main() {
for(Integer i : list) {
}
}
}
Let's compile it with javac Whatever.java
,
And read the disassembled bytecode of main()
, using javap -c Whatever
:
public void main();
Code:
0: aload_0
1: getfield #4 // Field list:Ljava/util/List;
4: invokeinterface #5, 1 // InterfaceMethod java/util/List.iterator:()Ljava/util/Iterator;
9: astore_1
10: aload_1
11: invokeinterface #6, 1 // InterfaceMethod java/util/Iterator.hasNext:()Z
16: ifeq 32
19: aload_1
20: invokeinterface #7, 1 // InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object;
25: checkcast #8 // class java/lang/Integer
28: astore_2
29: goto 10
32: return
We can see that foreach
compiles down to a program which:
- Creates iterator using
List.iterator()
- If
Iterator.hasNext()
: invokes Iterator.next()
and continues loop
As for "why doesn't this useless loop get optimized out of the compiled code? we can see that it doesn't do anything with the list item": well, it's possible for you to code your iterable such that .iterator()
has side-effects, or so that .hasNext()
has side-effects or meaningful consequences.
You could easily imagine that an iterable representing a scrollable query from a database might do something dramatic on .hasNext()
(like contacting the database, or closing a cursor because you've reached the end of the result set).
So, even though we can prove that nothing happens in the loop body… it is more expensive (intractable?) to prove that nothing meaningful/consequential happens when we iterate. The compiler has to leave this empty loop body in the program.
The best we could hope for would be a compiler warning. It's interesting that javac -Xlint:all Whatever.java
does not warn us about this empty loop body. IntelliJ IDEA does though. Admittedly I have configured IntelliJ to use Eclipse Compiler, but that may not be the reason why.
Matrix multiplication in OpenCV
You say that the matrices are the same dimensions, and yet you are trying to perform matrix multiplication on them. Multiplication of matrices with the same dimension is only possible if they are square. In your case, you get an assertion error, because the dimensions are not square. You have to be careful when multiplying matrices, as there are two possible meanings of multiply.
Matrix multiplication is where two matrices are multiplied directly. This operation multiplies matrix A of size [a x b] with matrix B of size [b x c] to produce matrix C of size [a x c]. In OpenCV it is achieved using the simple *
operator:
C = A * B
Element-wise multiplication is where each pixel in the output matrix is formed by multiplying that pixel in matrix A by its corresponding entry in matrix B. The input matrices should be the same size, and the output will be the same size as well. This is achieved using the mul()
function:
output = A.mul(B);
How to add google-play-services.jar project dependency so my project will run and present map
Be Careful, Follow these steps and save your time
Right Click on your Project Explorer.
Select New-> Project -> Android Application Project from Existing Code
Browse upto this path only - "C:\Users**your path**\Local\Android\android-sdk\extras\google\google_play_services"
Be careful brose only upto - google_play_services and not upto google_play_services_lib
And this way you are able to import the google play service lib.
Let me know if you have any queries regarding the same.
Thanks
CSS force image resize and keep aspect ratio
To maintain a responsive image while still enforcing the image to have a certain aspect ratio you can do the following:
HTML:
<div class="ratio2-1">
<img src="../image.png" alt="image">
</div>
And SCSS:
.ratio2-1 {
overflow: hidden;
position: relative;
&:before {
content: '';
display: block;
padding-top: 50%; // ratio 2:1
}
img {
position: absolute;
top: 0;
left: 0;
bottom: 0;
right: 0;
}
}
This can be used to enforce a certain aspect ratio, regardless of the size of the image that authors upload.
Thanks to @Kseso at http://codepen.io/Kseso/pen/bfdhg. Check this URL for more ratios and a working example.
C# function to return array
public static ArtworkData[] GetDataRecords(int UsersID)
{
ArtworkData[] Labels;
Labels = new ArtworkData[3];
return Labels;
}
This should work.
You only use the brackets when creating an array or accessing an array. Also, Array[]
is returning an array of array. You need to return the typed array ArtworkData[]
.
Converting File to MultiPartFile
File file = new File("src/test/resources/validation.txt");
DiskFileItem fileItem = new DiskFileItem("file", "text/plain", false, file.getName(), (int) file.length() , file.getParentFile());
fileItem.getOutputStream();
MultipartFile multipartFile = new CommonsMultipartFile(fileItem);
You need the
fileItem.getOutputStream();
because it will throw NPE otherwise.
Jquery Ajax, return success/error from mvc.net controller
Use Json
class instead of Content
as shown following:
// When I want to return an error:
if (!isFileSupported)
{
Response.StatusCode = (int) HttpStatusCode.BadRequest;
return Json("The attached file is not supported", MediaTypeNames.Text.Plain);
}
else
{
// When I want to return sucess:
Response.StatusCode = (int)HttpStatusCode.OK;
return Json("Message sent!", MediaTypeNames.Text.Plain);
}
Also set contentType:
contentType: 'application/json; charset=utf-8',
How to compare values which may both be null in T-SQL
Above, @drowa shows a verbose approach that I agree with. It's good because it avoids the 3-value logic problem. Many of the other approaches provided here will fail in subtle and unexpected ways when negated because they're treating null
as equivalent to false
which it is not.
However, I have a workflow that I find makes it convenient-ish, here's a regex. Given code of the form
(leftSide <=> rightSide)
regex find this:
\(([a-zA-Z0-9_.@]+)\s*<=>\s*([a-zA-Z0-9_.@]+)\)
and replace with this:
(/*$1 <=> $2*/ ($1 IS NULL AND $2 IS NULL) OR ($1 IS NOT NULL AND $2 IS NOT NULL AND $1 = $2))
So I write the (leftSide <=> rightSide)
code and apply the above regex transformation to get the expanded form. It'd be nicer if MSSQL offered some kind of macro expansion so I wouldn't have to do it manually, but it doesn't.
@Drowa's answer quoted for reference:
Equals comparison:
((f1 IS NULL AND f2 IS NULL) OR (f1 IS NOT NULL AND f2 IS NOT NULL AND f1 = f2))
Not Equal To comparison: Just negate the Equals comparison above.
NOT ((f1 IS NULL AND f2 IS NULL) OR (f1 IS NOT NULL AND f2 IS NOT NULL AND f1 = f2))
Is it verbose? Yes, it is. However it's efficient since it doesn't
call any function. The idea is to use short circuit in predicates to
make sure the equal operator (=) is used only with non-null values,
otherwise null would propagate up in the expression tree.
How to use HTTP_X_FORWARDED_FOR properly?
If you use it in a database, this is a good way:
Set the ip field in database to varchar(250), and then use this:
$theip = $_SERVER["REMOTE_ADDR"];
if (!empty($_SERVER["HTTP_X_FORWARDED_FOR"])) {
$theip .= '('.$_SERVER["HTTP_X_FORWARDED_FOR"].')';
}
if (!empty($_SERVER["HTTP_CLIENT_IP"])) {
$theip .= '('.$_SERVER["HTTP_CLIENT_IP"].')';
}
$realip = substr($theip, 0, 250);
Then you just check $realip against the database ip field
performSelector may cause a leak because its selector is unknown
Strange but true: if acceptable (i.e. result is void and you don't mind letting the runloop cycle once), add a delay, even if this is zero:
[_controller performSelector:NSSelectorFromString(@"someMethod")
withObject:nil
afterDelay:0];
This removes the warning, presumably because it reassures the compiler that no object can be returned and somehow mismanaged.
Untrack files from git temporarily
I am assuming that you are asking how to remove ALL the files in the build folder or the bin folder, Rather than selecting each files separately.
You can use this command:
git rm -r -f /build\*
Make sure that you are in the parent directory of the build directory.
This command will, recursively "delete" all the files which are in the bin/ or build/ folders. By the word delete I mean that git will pretend that those files are "deleted" and those files will not be tracked. The git really marks those files to be in delete mode.
Do make sure that you have your .gitignore ready for upcoming commits.
Documentation : git rm
CSS: auto height on containing div, 100% height on background div inside containing div
Just a quick note because I had a hard time with this.
By using #container { overflow: hidden; } the page I had started to have layout issues in Firefox and IE (when the zoom would go in and out the content would bounce in and out of the parent div).
The solution to this issue is to add a display: inline-block; to the same div with overflow:hidden;
REST - HTTP Post Multipart with JSON
If I understand you correctly, you want to compose a multipart request manually from an HTTP/REST console. The multipart format is simple; a brief introduction can be found in the HTML 4.01 spec. You need to come up with a boundary, which is a string not found in the content, let’s say HereGoes
. You set request header Content-Type: multipart/form-data; boundary=HereGoes
. Then this should be a valid request body:
--HereGoes
Content-Disposition: form-data; name="myJsonString"
Content-Type: application/json
{"foo": "bar"}
--HereGoes
Content-Disposition: form-data; name="photo"
Content-Type: image/jpeg
Content-Transfer-Encoding: base64
<...JPEG content in base64...>
--HereGoes--
Calling a rest api with username and password - how to
You can also use the RestSharp library
for example
var userName = "myuser";
var password = "mypassword";
var host = "170.170.170.170:333";
var client = new RestClient("https://" + host + "/method1");
client.Authenticator = new HttpBasicAuthenticator(userName, password);
var request = new RestRequest(Method.POST);
request.AddHeader("Accept", "application/json");
request.AddHeader("Cache-Control", "no-cache");
request.AddHeader("Content-Type", "application/json");
request.AddParameter("application/json","{}",ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
Running Tensorflow in Jupyter Notebook
It is better to create new environment with new name ($newenv):conda create -n $newenv tensorflow
Then by using anaconda navigator under environment tab you can find newenv in the middle column.
By clicking on the play button open terminal and type: activate tensorflow
Then install tensorflow inside the newenv by typing: pip install tensorflow
Now you have tensorflow inside the new environment so then install jupyter by typing: pip install jupyter notebook
Then just simply type: jupyter notebook
to run the jupyter notebook.
Inside of the jupyter notebook type: import tensorflow as tf
To test the the tf you can use THIS LINK
How do I change the font size and color in an Excel Drop Down List?
You cannot change the default but there is a codeless workaround.
Select the whole sheet and change the font size on your data to something small, like 10 or 12.
When you zoom in to view the data you will find that the drop down box entries are now visible.
To emphasize, the issue is not so much with the size of the font in the drop down, it is the relative size between drop down and data display font sizes.
How to get URL parameter using jQuery or plain JavaScript?
If you want to find a specific parameter from a specific url:
function findParam(url, param){
var check = "" + param;
if(url.search(check )>=0){
return url.substring(url.search(check )).split('&')[0].split('=')[1];
}
}
var url = "http://www.yourdomain.com/example?id=1&order_no=114&invoice_no=254";
alert(findParam(url,"order_no"));
How to generate components in a specific folder with Angular CLI?
The above options were not working for me because unlike creating a directory or file in the terminal, when the CLI generates a component, it adds the path src/app by default to the path you enter.
If I generate the component from my main app folder like so (WRONG WAY)
ng g c ./src/app/child/grandchild
the component that was generated was this:
src/app/src/app/child/grandchild.component.ts
so I only had to type
ng g c child/grandchild
Hopefully this helps someone
Sample settings.xml
A standard Maven
settings.xml
file is as follows:
<settings xmlns="http://maven.apache.org/SETTINGS/1.1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.1.0 http://maven.apache.org/xsd/settings-1.1.0.xsd">
<localRepository/>
<interactiveMode/>
<usePluginRegistry/>
<offline/>
<proxies>
<proxy>
<active/>
<protocol/>
<username/>
<password/>
<port/>
<host/>
<nonProxyHosts/>
<id/>
</proxy>
</proxies>
<servers>
<server>
<username/>
<password/>
<privateKey/>
<passphrase/>
<filePermissions/>
<directoryPermissions/>
<configuration/>
<id/>
</server>
</servers>
<mirrors>
<mirror>
<mirrorOf/>
<name/>
<url/>
<layout/>
<mirrorOfLayouts/>
<id/>
</mirror>
</mirrors>
<profiles>
<profile>
<activation>
<activeByDefault/>
<jdk/>
<os>
<name/>
<family/>
<arch/>
<version/>
</os>
<property>
<name/>
<value/>
</property>
<file>
<missing/>
<exists/>
</file>
</activation>
<properties>
<key>value</key>
</properties>
<repositories>
<repository>
<releases>
<enabled/>
<updatePolicy/>
<checksumPolicy/>
</releases>
<snapshots>
<enabled/>
<updatePolicy/>
<checksumPolicy/>
</snapshots>
<id/>
<name/>
<url/>
<layout/>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<releases>
<enabled/>
<updatePolicy/>
<checksumPolicy/>
</releases>
<snapshots>
<enabled/>
<updatePolicy/>
<checksumPolicy/>
</snapshots>
<id/>
<name/>
<url/>
<layout/>
</pluginRepository>
</pluginRepositories>
<id/>
</profile>
</profiles>
<activeProfiles/>
<pluginGroups/>
</settings>
To access a proxy
, you can find detailed information on the official Maven
page here:
Maven-Settings - Settings
I hope it helps for someone.
How to change the Text color of Menu item in Android?
Simply add this to your theme
<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
<item name="android:itemTextAppearance">@style/AppTheme.ItemTextStyle</item>
</style>
<style name="AppTheme.ItemTextStyle" parent="@android:style/TextAppearance.Widget.IconMenu.Item">
<item name="android:textColor">@color/orange_500</item>
</style>
Tested on API 21
How to pass values across the pages in ASP.net without using Session
You can pass values from one page to another by followings..
Response.Redirect
Cookies
Application Variables
HttpContext
Response.Redirect
SET :
Response.Redirect("Defaultaspx?Name=Pandian");
GET :
string Name = Request.QueryString["Name"];
Cookies
SET :
HttpCookie cookName = new HttpCookie("Name");
cookName.Value = "Pandian";
GET :
string name = Request.Cookies["Name"].Value;
Application Variables
SET :
Application["Name"] = "pandian";
GET :
string Name = Application["Name"].ToString();
Refer the full content here : Pass values from one to another
python numpy/scipy curve fitting
You'll first need to separate your numpy array into two separate arrays containing x and y values.
x = [1, 2, 3, 9]
y = [1, 4, 1, 3]
curve_fit also requires a function that provides the type of fit you would like. For instance, a linear fit would use a function like
def func(x, a, b):
return a*x + b
scipy.optimize.curve_fit(func, x, y)
will return a numpy array containing two arrays: the first will contain values for a
and b
that best fit your data, and the second will be the covariance of the optimal fit parameters.
Here's an example for a linear fit with the data you provided.
import numpy as np
from scipy.optimize import curve_fit
x = np.array([1, 2, 3, 9])
y = np.array([1, 4, 1, 3])
def fit_func(x, a, b):
return a*x + b
params = curve_fit(fit_func, x, y)
[a, b] = params[0]
This code will return a = 0.135483870968
and b = 1.74193548387
Here's a plot with your points and the linear fit... which is clearly a bad one, but you can change the fitting function to obtain whatever type of fit you would like.
Algorithm: efficient way to remove duplicate integers from an array
After review the problem, here is my delphi way, that may help
var
A: Array of Integer;
I,J,C,K, P: Integer;
begin
C:=10;
SetLength(A,10);
A[0]:=1; A[1]:=4; A[2]:=2; A[3]:=6; A[4]:=3; A[5]:=4;
A[6]:=3; A[7]:=4; A[8]:=2; A[9]:=5;
for I := 0 to C-1 do
begin
for J := I+1 to C-1 do
if A[I]=A[J] then
begin
for K := C-1 Downto J do
if A[J]<>A[k] then
begin
P:=A[K];
A[K]:=0;
A[J]:=P;
C:=K;
break;
end
else
begin
A[K]:=0;
C:=K;
end;
end;
end;
//tructate array
setlength(A,C);
end;
How do I add a library project to Android Studio?
Option 1: Drop Files Into Project's libs/directory
The relevant build.gradle file will then update automatically.
Option 2: Modify build.gradle File Manually
Open your build.gradle file and add a new build rule to the dependencies closure. For example, if you wanted to add Google Play Services, your project's dependencies section would look something like this:
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.google.android.gms:play-services:6.5.+'
}
Option 3: Use Android Studio's User Interface
In the Project panel, Control + click the module you want to add the dependency to and select Open Module Settings.
Select the Dependencies tab, followed by the + button in the bottom-left corner. You can choose from the following list of options:
- Library Dependency
- File Dependency
- Module Dependency
You can then enter more information about the dependency you want to add to your project. For example, if you choose Library Dependency, Android Studio displays a list of libraries for you to choose from.
Once you've added your dependency, check your module-level build.gradle file. It should have automatically updated to include the new dependency.
Source
Combine two OR-queries with AND in Mongoose
It's probably easiest to create your query object directly as:
Test.find({
$and: [
{ $or: [{a: 1}, {b: 1}] },
{ $or: [{c: 1}, {d: 1}] }
]
}, function (err, results) {
...
}
But you can also use the Query#and
helper that's available in recent 3.x Mongoose releases:
Test.find()
.and([
{ $or: [{a: 1}, {b: 1}] },
{ $or: [{c: 1}, {d: 1}] }
])
.exec(function (err, results) {
...
});
How to unlock android phone through ADB
Below commands works both when screen is on and off
To lock the screen:
adb shell input keyevent 82 && adb shell input keyevent 26 && adb shell input keyevent 26
To lock the screen and turn it off
adb shell input keyevent 82 && adb shell input keyevent 26
To unlock the screen without pass
adb shell input keyevent 82 && adb shell input keyevent 66
To unlock the screen that has pass 1234
adb shell input keyevent 82 && adb shell input text 1234 && adb shell input keyevent 66
Pass value to iframe from a window
What you have to do is to append the values as parameters in the iframe src (URL).
E.g. <iframe src="some_page.php?somedata=5&more=bacon"></iframe>
And then in some_page.php
file you use php $_GET['somedata']
to retrieve it from the iframe URL. NB: Iframes run as a separate browser window in your file.
how to use "AND", "OR" for RewriteCond on Apache?
Having trouble wrapping my head around this.
Have a rewrite rule with four conditions.
The first three conditions A, B, C are to be AND which is then OR with D
RewriteCond A true
RewriteCond B false
RewriteCond C [OR] true
RewriteCond D true
RewriteRule ...
But that seems to be an expression of
A and B and (C or D) = false (don't rewrite)
How can I get to the desired expression?
(A and B and C) or D = true (rewrite)
Preferably without using the additional steps of setting environment variables.
HELP!!!
Adding a UISegmentedControl to UITableView
self.tableView.tableHeaderView = segmentedControl;
If you want it to obey your width and height properly though enclose your segmentedControl in a UIView first as the tableView likes to mangle your view a bit to fit the width.
Changing the sign of a number in PHP?
re the edit: "Also i need a way to do the reverse If the float is a negative, make it a positive"
$number = -$number;
changes the number to its opposite.
jQuery changing font family and font size
Full working solution :
HTML:
<form id="myform">
<button>erase</button>
<select id="fs">
<option value="Arial">Arial</option>
<option value="Verdana ">Verdana </option>
<option value="Impact ">Impact </option>
<option value="Comic Sans MS">Comic Sans MS</option>
</select>
<select id="size">
<option value="7">7</option>
<option value="10">10</option>
<option value="20">20</option>
<option value="30">30</option>
</select>
</form>
<br/>
<textarea class="changeMe">Text into textarea</textarea>
<div id="container" class="changeMe">
<div id="float">
<p>
Text into container
</p>
</div>
</div>
jQuery:
$("#fs").change(function() {
//alert($(this).val());
$('.changeMe').css("font-family", $(this).val());
});
$("#size").change(function() {
$('.changeMe').css("font-size", $(this).val() + "px");
});
Fiddle here: http://jsfiddle.net/AaT9b/
"Fatal error: Unable to find local grunt." when running "grunt" command
I had the same issue today on windows 32 bit,with node 0.10.25, and grunt 0.4.5.
I followed dongho's answer, with just few extra steps.
here are the steps I used to solve the error:
1) create your package.json
$ npm init
2) install grunt for this project, this will be installed under node_modules/. --save-dev will add this module to devDependency in your package.json
$ npm install grunt --save-dev
3) then create gruntfile.js
, with a sample code like this:
module.exports = function(grunt) {
grunt.initConfig({
jshint: {
files: ['Gruntfile.js', 'src/**/*.js', 'test/**/*.js'],
options: {
globals: {
jQuery: true
}
}
},
watch: {
files: ['<%= jshint.files %>'],
tasks: ['jshint']
}
});
grunt.loadNpmTasks('grunt-contrib-jshint');
grunt.loadNpmTasks('grunt-contrib-watch');
grunt.registerTask('default', ['jshint']);
};
here, src/**/*.js
and test/**/*.js
should be the paths to actual JS files you are using in your project
4) run npm install grunt-contrib-jshint --save-dev
5) run npm install grunt-contrib-watch --save-dev
6) run $ grunt
Note: when you require common package like concat, uglify etc, you need to add those modules via npm install
, just the way we installed jshint and watch in step 4 & 5
How to use regex with find command?
Judging from other answers, it seems this might be find's fault.
However you can do it this way instead:
find . * | grep -P "[a-f0-9\-]{36}\.jpg"
You might have to tweak the grep a bit and use different options depending on what you want but it works.
How to make a Java Generic method static?
I'll explain it in a simple way.
Generics defined at Class level are completely separate from the generics defined at the (static) method level.
class Greet<T> {
public static <T> void sayHello(T obj) {
System.out.println("Hello " + obj);
}
}
When you see the above code anywhere, please note that the T defined at the class level has nothing to do with the T defined in the static method. The following code is also completely valid and equivalent to the above code.
class Greet<T> {
public static <E> void sayHello(E obj) {
System.out.println("Hello " + obj);
}
}
Why the static method needs to have its own generics separate from those of the Class?
This is because, the static method can be called without even
instantiating the Class. So if the Class is not yet instantiated, we
do not yet know what is T. This is the reason why the static methods
needs to have its own generics.
So, whenever you are calling the static method,
Greet.sayHello("Bob");
Greet.sayHello(123);
JVM interprets it as the following.
Greet.<String>sayHello("Bob");
Greet.<Integer>sayHello(123);
Both giving the same outputs.
Hello Bob
Hello 123
static and extern global variables in C and C++
Global variables are not extern
nor static
by default on C and C++.
When you declare a variable as static
, you are restricting it to the current source file. If you declare it as extern
, you are saying that the variable exists, but are defined somewhere else, and if you don't have it defined elsewhere (without the extern
keyword) you will get a link error (symbol not found).
Your code will break when you have more source files including that header, on link time you will have multiple references to varGlobal
. If you declare it as static
, then it will work with multiple sources (I mean, it will compile and link), but each source will have its own varGlobal
.
What you can do in C++, that you can't in C, is to declare the variable as const
on the header, like this:
const int varGlobal = 7;
And include in multiple sources, without breaking things at link time. The idea is to replace the old C style #define
for constants.
If you need a global variable visible on multiple sources and not const
, declare it as extern
on the header, and then define it, this time without the extern keyword, on a source file:
Header included by multiple files:
extern int varGlobal;
In one of your source files:
int varGlobal = 7;
How to use ArrayAdapter<myClass>
Implement custom adapter for your class:
public class MyClassAdapter extends ArrayAdapter<MyClass> {
private static class ViewHolder {
private TextView itemView;
}
public MyClassAdapter(Context context, int textViewResourceId, ArrayList<MyClass> items) {
super(context, textViewResourceId, items);
}
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = LayoutInflater.from(this.getContext())
.inflate(R.layout.listview_association, parent, false);
viewHolder = new ViewHolder();
viewHolder.itemView = (TextView) convertView.findViewById(R.id.ItemView);
convertView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) convertView.getTag();
}
MyClass item = getItem(position);
if (item!= null) {
// My layout has only one TextView
// do whatever you want with your string and long
viewHolder.itemView.setText(String.format("%s %d", item.reason, item.long_val));
}
return convertView;
}
}
For those not very familiar with the Android framework, this is explained in better detail here: https://github.com/codepath/android_guides/wiki/Using-an-ArrayAdapter-with-ListView.