Programs & Examples On #Data connections

Best TCP port number range for internal applications

Short answer: use an unassigned user port

Over achiever's answer - Select and deploy a resource discovery solution. Have the server select a private port dynamically. Have the clients use resource discovery.

The risk that that a server will fail because the port it wants to listen on is not available is real; at least it's happened to me. Another service or a client might get there first.

You can almost totally reduce the risk from a client by avoiding the private ports, which are dynamically handed out to clients.

The risk that from another service is minimal if you use a user port. An unassigned port's risk is only that another service happens to be configured (or dyamically) uses that port. But at least that's probably under your control.

The huge doc with all the port assignments, including User Ports, is here: look for the token Unassigned.

How Do I Take a Screen Shot of a UIView?

- (void)drawRect:(CGRect)rect {
  [self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
  UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
  UIImageWriteToSavedPhotosAlbum(viewImage, nil, nil, nil);  

This method may put in your Controller class.

How to find substring from string?

Use strstr(const char *s , const char *t) and include<string.h>

You can write your own function which behaves same as strstr and you can modify according to your requirement also

char * str_str(const char *s, const char *t)
int i, j, k;
for (i = 0; s[i] != '\0'; i++) 
for (j=i, k=0; t[k]!='\0' && s[j]==t[k]; j++, k++);
if (k > 0 && t[k] == '\0')
return (&s[i]);
return NULL;

Mockito: List Matchers with generics

In addition to anyListOf above, you can always specify generics explicitly using this syntax:


Java 8 newly allows type inference based on parameters, so if you're using Java 8, this may work as well:


Remember that neither any() nor anyList() will apply any checks, including type or null checks. In Mockito 2.x, any(Foo.class) was changed to mean "any instanceof Foo", but any() still means "any value including null".

NOTE: The above has switched to ArgumentMatchers in newer versions of Mockito, to avoid a name collision with org.hamcrest.Matchers. Older versions of Mockito will need to keep using org.mockito.Matchers as above.

How to define an enum with string value?

A class that emulates enum behaviour but using string instead of int can be created as follows...

public class GrainType
    private string _typeKeyWord;

    private GrainType(string typeKeyWord)
        _typeKeyWord = typeKeyWord;

    public override string ToString()
        return _typeKeyWord;

    public static GrainType Wheat = new GrainType("GT_WHEAT");
    public static GrainType Corn = new GrainType("GT_CORN");
    public static GrainType Rice = new GrainType("GT_RICE");
    public static GrainType Barley = new GrainType("GT_BARLEY");



GrainType myGrain = GrainType.Wheat;



public void PrintGrainKeyword(GrainType grain) 
    Console.Writeline("My Grain code is " + grain.ToString());   // Displays "My Grain code is GT_WHEAT"

Load local JSON file into variable

There are two possible problems:

  1. AJAX is asynchronous, so json will be undefined when you return from the outer function. When the file has been loaded, the callback function will set json to some value but at that time, nobody cares anymore.

    I see that you tried to fix this with 'async': false. To check whether this works, add this line to the code and check your browser's console:

    console.log(['json', json]);
  2. The path might be wrong. Use the same path that you used to load your script in the HTML document. So if your script is js/script.js, use js/content.json

    Some browsers can show you which URLs they tried to access and how that went (success/error codes, HTML headers, etc). Check your browser's development tools to see what happens.

Artificially create a connection timeout error


All these are non-routable.

Oracle Age calculation from Date of birth and Today

Age (full years) of the Person:

  TRUNC(months_between(sysdate, per.DATE_OF_BIRTH) / 12) AS "Age"

Python: Fetch first 10 results from a list

check this

 list = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]



[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

UIViewController viewDidLoad vs. viewWillAppear: What is the proper division of labor?

Depends, Do you need the data to be loaded each time you open the view? or only once?

enter image description here

  • Red : They don't require to change every time. Once they are loaded they stay as how they were.
  • Purple: They need to change over time or after you load each time. You don't want to see the same 3 suggested users to follow, it needs to be reloaded every time you come back to the screen. Their photos may get updated... you don't want to see a photo from 5 years ago...

viewDidLoad: Whatever processing you have that needs to be done once.
viewWilLAppear: Whatever processing that needs to change every time the page is loaded.

Labels, icons, button titles or most dataInputedByDeveloper usually don't change. Names, photos, links, button status, lists (input Arrays for your tableViews or collectionView) or most dataInputedByUser usually do change.

How can I upload files asynchronously?

Note: This answer is outdated, it is now possible to upload files using XHR.

You cannot upload files using XMLHttpRequest (Ajax). You can simulate the effect using an iframe or Flash. The excellent jQuery Form Plugin that posts your files through an iframe to get the effect.

Convert date field into text in Excel

If that is one table and have nothing to do with this - the simplest solution can be copy&paste to notepad then copy&paste back to excel :P

"Fade" borders in CSS

Add this class css to your style sheet

.border_gradient {
border: 8px solid #000;
-moz-border-bottom-colors:#897048 #917953 #a18a66 #b6a488 #c5b59b #d4c5ae #e2d6c4 #eae1d2;
-moz-border-top-colors:#897048 #917953 #a18a66 #b6a488 #c5b59b #d4c5ae #e2d6c4 #eae1d2;
-moz-border-left-colors:#897048 #917953 #a18a66 #b6a488 #c5b59b #d4c5ae #e2d6c4 #eae1d2;
-moz-border-right-colors:#897048 #917953 #a18a66 #b6a488 #c5b59b #d4c5ae #e2d6c4 #eae1d2;
padding: 5px 5px 5px 15px;
width: 300px;

set width to the width of your image. and use this html for image

<div class="border_gradient">
        <img src="image.png" />

though it may not give the same exact border, it will some gradient looks on the border.

source: CSS3 Borders

In c# what does 'where T : class' mean?

That restricts T to reference types. You won't be able to put value types (structs and primitive types except string) there.

Move column by name to front of table in pandas

You can use the df.reindex() function in pandas. df is

                      Net  Upper   Lower  Mid  Zsore
Answer option                                      
More than once a day  0%  0.22%  -0.12%    2     65
Once a day            0%  0.32%  -0.19%    3     45
Several times a week  2%  2.45%   1.10%    4     78
Once a week           1%  1.63%  -0.40%    6     65

define an list of column names

cols = df.columns.tolist()
Out[13]: ['Net', 'Upper', 'Lower', 'Mid', 'Zsore']

move the column name to wherever you want

cols.insert(0, cols.pop(cols.index('Mid')))
Out[16]: ['Mid', 'Net', 'Upper', 'Lower', 'Zsore']

then use df.reindex() function to reorder

df = df.reindex(columns= cols)

out put is: df

                      Mid  Upper   Lower Net  Zsore
Answer option                                      
More than once a day    2  0.22%  -0.12%  0%     65
Once a day              3  0.32%  -0.19%  0%     45
Several times a week    4  2.45%   1.10%  2%     78
Once a week             6  1.63%  -0.40%  1%     65

python paramiko ssh

The code of @ThePracticalOne is great for showing the usage except for one thing: Somtimes the output would be incomplete.(session.recv_ready() turns true after the if session.recv_ready(): while session.recv_stderr_ready() and session.exit_status_ready() turned true before entering next loop)

so my thinking is to retrieving the data when it is ready to exit the session.

while True:
if session.exit_status_ready():
while True:
    while True:
        print "try to recv stdout..."
        ret = session.recv(nbytes)
        if len(ret) == 0:

    while True:
        print "try to recv stderr..."
        ret = session.recv_stderr(nbytes)
        if len(ret) == 0:

How to convert array into comma separated string in javascript

Use the join method from the Array type.

a.value = [a, b, c, d, e, f];
var stringValueYouWant = a.join();

The join method will return a string that is the concatenation of all the array elements. It will use the first parameter you pass as a separator - if you don't use one, it will use the default separator, which is the comma.

Get underlined text with Markdown

You can wrote **_bold and italic_** and re-style it to underlined text, like this:

i>b {

How do I filter an array with TypeScript in Angular 2?

You can check an example in Plunker over here plunker example filters

filter() {

    let storeId = 1;
    this.bookFilteredList = this.bookList
                                .filter((book: Book) => book.storeId === storeId);
    this.bookList = this.bookFilteredList; 

Maven Install on Mac OS X

Disclaimer: Here is a complete answer taking the last version of OS X (10.9 AKA Mavericks) into account. I am aware that everything I compiled in this answer is already present in the page, but having it clearly in one answer makes it a lot clearer.

First of all, with previous versions of OS X, Maven is installed by default. If Java is missing running you@host:~ $ java in a terminal will prompt you for the Java installation.

With Mac OS X 10.9 (Mavericks), Maven is not installed by default anymore. Different options are then possible:

  • Using Homebrew:
    • you@host:~$ brew install maven will install latest Maven (3.5.2 on 02/01/2018)
    • you@host:~$ brew install maven30 will install Maven 3.0 if needed
  • Using Macports: (I did not test this)
    • you@host:~$ sudo port install maven will install latest Maven (?)
    • or:
    • you@host:~$ sudo port install maven3 will Install Maven 3.0
    • you@host:~$ sudo port select --set maven maven3 selects that version of Maven
  • Installing by hand:
    • Download Maven from its homepage
    • Follow the installation instructions:
      1. Extract the distribution archive, i.e.apache-maven-3.3.9-bin.tar.gz to the directory you wish to install Maven 3.3.9. The subdirectory apache-maven-3.3.9 will be created from the archive.
      2. Optional: Add the MAVEN_OPTS environment variable to specify JVM properties, e.g. export MAVEN_OPTS="-Xms256m -Xmx512m". This environment variable can be used to supply extra options to Maven.
      3. Make sure that JAVA_HOME is set to the location of your JDK, e.g. export JAVA_HOME=$(/usr/libexec/java_home -v 1.8) and that $JAVA_HOME/bin is in your PATH environment variable (although that might not be necessary with the latest Mac OS X versions and the Oracle JDK).
      4. Add extracted apache-maven-3.3.9/bin to your $PATH
      5. Run mvn --version to verify that it is correctly installed.

How can I loop through enum values for display in radio buttons?

Two options:

for (let item in MotifIntervention) {
    if (isNaN(Number(item))) {


Object.keys(MotifIntervention).filter(key => !isNaN(Number(MotifIntervention[key])));

(code in playground)


String enums look different than regular ones, for example:

enum MyEnum {
    A = "a",
    B = "b",
    C = "c"

Compiles into:

var MyEnum;
(function (MyEnum) {
    MyEnum["A"] = "a";
    MyEnum["B"] = "b";
    MyEnum["C"] = "c";
})(MyEnum || (MyEnum = {}));

Which just gives you this object:

    A: "a",
    B: "b",
    C: "c"

You can get all the keys (["A", "B", "C"]) like this:


And the values (["a", "b", "c"]):

Object.keys(MyEnum).map(key => MyEnum[key])

Or using Object.values():


Stop node.js program from command line

If you want to stop your server with npm stop or something like this. You can write the code that kill your server process as:

require('child_process').exec(`kill -9 ${pid}`)

Check this link for the detail:

Trying to make bootstrap modal wider

Always have handy the un-minified CSS for bootstrap so you can see what styles they have on their components, then create a CSS file AFTER it, if you don't use LESS and over-write their mixins or whatever

This is the default modal css for 768px and up:

@media (min-width: 768px) {
  .modal-dialog {
    width: 600px;
    margin: 30px auto;

They have a class modal-lg for larger widths

@media (min-width: 992px) {
  .modal-lg {
    width: 900px;

If you need something twice the 600px size, and something fluid, do something like this in your CSS after the Bootstrap css and assign that class to the modal-dialog.

@media (min-width: 768px) {
  .modal-xl {
    width: 90%;


<div class="modal-dialog modal-xl">


Keep background image fixed during scroll using css

background-image: url("/your-dir/your_image.jpg");
min-height: 100%;
background-repeat: no-repeat;
background-attachment: fixed;
background-position: center;
background-size: cover;}

Recyclerview and handling different type of row inflation

We can achieve multiple view on single RecyclerView from below way :-

Dependencies on Gradle so add below code:-

compile ''
compile ''

RecyclerView in XML


Activity Code

private RecyclerView mRecyclerView;
private CustomAdapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
private String[] mDataset = {“Data - one ”, “Data - two”,
    “Showing data three”, “Showing data four”};
private int mDatasetTypes[] = {DataOne, DataTwo, DataThree}; //view types
mRecyclerView = (RecyclerView) findViewById(;
mLayoutManager = new LinearLayoutManager(MainActivity.this);
//Adapter is created in the last step
mAdapter = new CustomAdapter(mDataset, mDataSetTypes);

First XML

<?xml version="1.0" encoding="utf-8"?>
< xmlns:android=""
            android:textColor=“@color/white“ />
            android:textSize="30sp" />

Second XML

<?xml version="1.0" encoding="utf-8"?>
< xmlns:android=""
            android:textColor="@color/white" />
            android:textSize="30sp" />

Third XML

<?xml version="1.0" encoding="utf-8"?>
< xmlns:android=""
            android:text=“DataThree” />
            android:textSize="25sp" />
            android:text=“Show More” />

Now time to make adapter and this is main for showing different -2 view on same recycler view so please check this code focus fully :-

public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.ViewHolder> {
    private static final String TAG = "CustomAdapter";
    private String[] mDataSet;
    private int[] mDataSetTypes;
    public static final int dataOne = 0;
    public static final int dataTwo = 1;
    public static final int dataThree = 2;
    public static class ViewHolder extends RecyclerView.ViewHolder {
        public ViewHolder(View v) {
    public class DataOne extends ViewHolder {
        TextView temp;
        public DataOne(View v) {
            this.temp = (TextView) v.findViewById(;
    public class DataTwo extends ViewHolder {
        TextView score;
        public DataTwo(View v) {
            this.score = (TextView) v.findViewById(;
    public class DataThree extends ViewHolder {
        TextView headline;
        Button read_more;
        public DataThree(View v) {
            this.headline = (TextView) v.findViewById(;
            this.read_more = (Button) v.findViewById(;
    public CustomAdapter(String[] dataSet, int[] dataSetTypes) {
        mDataSet = dataSet;
        mDataSetTypes = dataSetTypes;
    public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
        View v;
        if (viewType == dataOne) {
            v = LayoutInflater.from(viewGroup.getContext())
                    .inflate(R.layout.weather_card, viewGroup, false);
            return new DataOne(v);
        } else if (viewType == dataTwo) {
            v = LayoutInflater.from(viewGroup.getContext())
                    .inflate(R.layout.news_card, viewGroup, false);
            return new DataThree(v);
        } else {
            v = LayoutInflater.from(viewGroup.getContext())
                    .inflate(R.layout.score_card, viewGroup, false);
            return new DataTwo(v);
    public void onBindViewHolder(ViewHolder viewHolder, final int position) {
        if (viewHolder.getItemViewType() == dataOne) {
            DataOne holder = (DataOne) viewHolder;
        else if (viewHolder.getItemViewType() == dataTwo) {
            DataThree holder = (DataTwo) viewHolder;
        else {
            DataTwo holder = (DataTwo) viewHolder;
    public int getItemCount() {
        return mDataSet.length;
    public int getItemViewType(int position) {
        return mDataSetTypes[position];

You can check also this link for more information.

Finding the index of elements based on a condition using python list comprehension

Maybe another question is, "what are you going to do with those indices once you get them?" If you are going to use them to create another list, then in Python, they are an unnecessary middle step. If you want all the values that match a given condition, just use the builtin filter:

matchingVals = filter(lambda x : x>2, a)

Or write your own list comprhension:

matchingVals = [x for x in a if x > 2]

If you want to remove them from the list, then the Pythonic way is not to necessarily remove from the list, but write a list comprehension as if you were creating a new list, and assigning back in-place using the listvar[:] on the left-hand-side:

a[:] = [x for x in a if x <= 2]

Matlab supplies find because its array-centric model works by selecting items using their array indices. You can do this in Python, certainly, but the more Pythonic way is using iterators and generators, as already mentioned by @EliBendersky.

Disabling browser print options (headers, footers, margins) from page?

Since you mentioned "within their browser" and firefox, if you are using Internet Explorer, you can disable the page header/footer by temporarily setting of the value in the registry, see here for an example. AFAIK I have not heard of a way to do this within other browsers. Both Daniel's and Mickel's answers seems to collide with each other, I guess that there could be a similar setting somewhere in the registry for firefox to remove headers/footers or customize them. Have you checked it out?

.c vs .cc vs. .cpp vs .hpp vs .h vs .cxx

Those extensions aren't really new, they are old. :-)

When C++ was new, some people wanted to have a .c++ extension for the source files, but that didn't work on most file systems. So they tried something close to that, like .cxx, or .cpp instead.

Others thought about the language name, and "incrementing" .c to get .cc or even .C in some cases. Didn't catch on that much.

Some believed that if the source is .cpp, the headers ought to be .hpp to match. Moderately successful.

Clear text field value in JQuery

$('#[element id]').val(null);


$('.[element class]').val(null);

How to get Spinner value?

Say this is your xml with spinner entries (ie. titles) and values:

    <string-array name="size_entries">

    <string-array name="size_values">

and this is your spinner:

    android:entries="@array/size_entries" />

Then in your code to get the entries:

Spinner spinner = (Spinner) findViewById(;
String size = spinner.getSelectedItem().toString(); // Small, Medium, Large

and to get the values:

int spinner_pos = spinner.getSelectedItemPosition();
String[] size_values = getResources().getStringArray(R.array.size_values);
int size = Integer.valueOf(size_values[spinner_pos]); // 12, 16, 20

How to add/update child entities when updating a parent entity in EF

OK guys. I had this answer once but lost it along the way. absolute torture when you know there's a better way but can't remember it or find it! It's very simple. I just tested it multiple ways.

var parent = _dbContext.Parents
  .Where(p => p.Id == model.Id)
  .Include(p => p.Children)

parent.Children = _dbContext.Children.Where(c => <Query for New List Here>);
_dbContext.Entry(parent).State = EntityState.Modified;


You can replace the whole list with a new one! The SQL code will remove and add entities as needed. No need to concern yourself with that. Be sure to include child collection or no dice. Good luck!

How can I check for IsPostBack in JavaScript?

Here is one way (put this in Page_Load):

if (this.IsPostBack)
    Page.ClientScript.RegisterStartupScript(this.GetType(),"PostbackKey","<script type='text/javascript'>var isPostBack = true;</script>");

Then just check that variable in the JS.

This could be due to the service endpoint binding not using the HTTP protocol

I've had this same error and the problem was serialization. I managed to find the real problem using Service Trace Viewer and solved it easy. Maybe this will help someone.

How can I read a large text file line by line using Java?

You can also use Apache Commons IO:

File file = new File("/home/user/file.txt");
try {
    List<String> lines = FileUtils.readLines(file);
} catch (IOException e) {
    // TODO Auto-generated catch block

Combating AngularJS executing controller twice

I tore my app and all its dependencies to bits over this issue (details here: AngularJS app initiating twice (tried the usual solutions..))

And in the end, it was all Batarang Chrome plugin's fault.

Resolution in this answer:

I'd strongly recommend the first thing on anyone's list is to disable it per the post before altering code.

ERROR: SQLSTATE[HY000] [2002] No connection could be made because the target machine actively refused it

If the WAMP icon is Orange then one of the services has not started.

In your case it looks like MySQL has not started as you are getting the message that indicates there is no server running and therefore listening for requests.

Look at the mysql log and if that tells you nothing look at the Windows event log, in the Windows -> Applications section. Error messages in there are pretty good at identifying the cause of MySQL failing to start.

Sometimes this is caused by a my.ini file from another install being picked up by WAMPServers MySQL, normally in the \windows or \windows\system32 folders. Do a search for 'my.ini' and 'my.cnf' and if you find one of these anywhere outside of the \wamp.... folder structure then delete it, or at least rename it so it wont be found. Then restart the MySQL service.

Angular ui-grid dynamically calculate height of the grid

I am late to the game but I found a nice solution. I created a custom attribute directive all you need to do is pass in the gridApi and it will automatically calculate the height. It also subscribes to the pagination change event so if the user changes page size it will resize.

class UIGridAutoResize implements ng.IDirective {
    link: (scope: ng.IScope, element: ng.IAugmentedJQuery, attrs: ng.IAttributes) => void;
    scope: { gridApi: "=" };
    restrict = "A";

    private previousValue: string;
    private isValid: boolean = true;
    private watch: any;

    constructor($timeout: ng.ITimeoutService) { = (scope: ng.IScope, element: ng.IAugmentedJQuery, attrs: ng.IAttributes) => {
            const gridOptions = scope.$eval(attrs.uiGrid) as any;
            const gridApi = scope.$eval(attrs.gridResize) as any;

            gridApi.core.on.rowsRendered(scope, () => {
                $timeout(() => {
                    this.autoSizeGrid(element, attrs, gridOptions, gridApi, false);
                }, 100);

            gridApi.core.on.filterChanged(scope, () => {
                this.autoSizeGrid(element, attrs, gridOptions, gridApi, false);

            if (attrs.uiGridPagination === "") {
                gridApi.pagination.on.paginationChanged(null, () => {
                    this.autoSizeGrid(element, attrs, gridOptions, gridApi, true);

            angular.element(window).resize(() => {
                $timeout(() => {
                    this.autoSizeGrid(element, attrs, gridOptions, gridApi, false);
                }, 100);

    static Factory(): ng.IDirectiveFactory {
        const directive = ($timeout: ng.ITimeoutService) => {
            return new UIGridAutoResize($timeout);

        directive["$inject"] = ["$timeout"];

        return directive;

    private autoSizeGrid(element: ng.IAugmentedJQuery, attrs: ng.IAttributes, gridOptions: any, gridApi: any, isPaginationChanged: boolean) {

        // Clear empty grid message 
        element.find(".ui-grid-viewport").css("display", "");

        if (attrs.hidePageSize === "") {
            element.find(".ui-grid-pager-row-count-picker").css("display", "none");

        let rowCount = gridApi.core.getVisibleRows().length;

        const headerElements = element.find(".ui-grid-header");
        let headerHeight = 2;

        if (headerElements.length > 1) { // If we have more than one header element the grid is using grouping
            const headerElement = angular.element(headerElements[1]);
            headerHeight += headerElement.height();
        } else {
            headerHeight += headerElements.height();

        if (attrs.uiGridPagination === "") {
            if (rowCount < 1) {
                gridOptions.enablePagination = false;
                gridOptions.enablePaginationControls = false;
                element.css("height", (rowCount * 30) + headerHeight - 2);
                element.find(".ui-grid-viewport").css("display", "none");
                angular.element("<div id='emptyGridMessage' style='font-size: 1em; width: 100%; background-color: white; border: 1px solid #d4d4d4; padding: 7px 12px; color: #707070;'><span style='opacity: 0.95;'>There are no records.</span></div>").insertAfter(element);
            } else if (gridApi.core.getVisibleRows().length < gridOptions.paginationPageSize && !isPaginationChanged) {
                gridOptions.enablePagination = false;
                gridOptions.enablePaginationControls = false;
                element.css("height", (rowCount * 30) + headerHeight);
            } else {
                gridOptions.enablePagination = true;
                gridOptions.enablePaginationControls = true;              
                element.css("height", (rowCount * 30) + headerHeight);
        } else {
            if (rowCount < 1) {
                element.css("height", (rowCount * 30) + headerHeight - 2);
                element.find(".ui-grid-viewport").css("display", "none");
                angular.element("<div id='emptyGridMessage' style='font-size: 1em; width: 100%; background-color: white; border: 1px solid #d4d4d4; padding: 7px 12px; color: #707070;'><span style='opacity: 0.95;'>There are no records.</span></div>").insertAfter(element);
            } else {
                element.css("height", (rowCount * 30) + headerHeight);

        // Add extra margin to prevent scroll bar and pager from overlapping content underneath
        const pagerHeight = element.find(".ui-grid-pager-panel").height();

        if (rowCount > 0) {
            if (pagerHeight > 0)
                element.css("margin-bottom", pagerHeight);
                element.css("margin-bottom", 10);
        } else {
            if (pagerHeight > 0)
                angular.element(element.parent()).find("#emptyGridMessage").css("margin-bottom", pagerHeight);
                angular.element(element.parent()).find("#emptyGridMessage").css("margin-bottom", 10);

        if (rowCount > gridOptions.paginationPageSize) // Sometimes paging shows all rows this fixes that
<div ui-grid="vm.gridOptions" grid-resize="vm.gridApi" ui-grid-resize-columns ui-grid-pagination></div>

Getting list of Facebook friends with latest API

This is live version of PHP Code to get your friends from Facebook

    $user = $facebook->getUser();

    if ($user) {
        $user_profile = $facebook->api('/me');
        $friends = $facebook->api('/me/friends');

        echo '<ul>';
        foreach ($friends["data"] as $value) {
            echo '<li>';
            echo '<div class="pic">';
            echo '<img src="' . $value["id"] . '/picture"/>';
            echo '</div>';
            echo '<div class="picName">'.$value["name"].'</div>'; 
            echo '</li>';
        echo '</ul>';

Can multiple different HTML elements have the same ID if they're different elements?

The official spec for HTML states that id tags must be unique AND the official spec also states that if the render can be completed, it must (i.e. there are no such thing as "errors" in HTML, only "invalid" HTML). So, the following is how id tags actually work in practice. They are all invalid, but still work:


<div id="unique">One</div>
<div id="unique">Two</div>

Renders fine in all browsers. However, document.getElementById only returns an object, not an array; you will only ever be able to select the first div via an id tag. If you were to change the id of the first div using JavaScript, the second ID would then be accessible with document.getElementById (tested on Chrome, FireFox & IE11). You can still select the div using other selection methods, and it's id property will be returned correctly.

Please note this above issue opens a potential security vulnerability in sites that render SVG images, as SVGs are allowed to contain DOM elements, and also id tags on them (allows script DOM redirects via uploaded images). As long as the SVG is positioned in the DOM before the element it replaces, the image will receive all JavaScript events meant for the other element.

This issue is currently not on anyone's radar as far as I know, yet it's real.


<div id="unique" id="unique-also">One</div>

Also renders fine in all browsers. However, only the first id you define this way is utilized, if you tried document.getElementById('unique-also'); in the above example, you would be returned null (tested on Chrome, FireFox & IE11).


<div id="unique unique-two">Two</div>

Also renders fine in all browsers, however, unlike class tags that can be separated by a space, the id tag allows spaces, so the id of the above element is actually "unique unique-two", and asking the dom for "unique" or "unique-two" in isolation returns null unless otherwise defined elsewhere in the DOM (tested on Chrome, FireFox & IE11).

Double array initialization in Java

This is array initializer syntax, and it can only be used on the right-hand-side when declaring a variable of array type. Example:

int[] x = {1,2,3,4};
String y = {"a","b","c"};

If you're not on the RHS of a variable declaration, use an array constructor instead:

int[] x;
x = new int[]{1,2,3,4};
String y;
y = new String[]{"a","b","c"};

These declarations have the exact same effect: a new array is allocated and constructed with the specified contents.

In your case, it might actually be clearer (less repetitive, but a bit less concise) to specify the table programmatically:

double[][] m = new double[4][4];

for(int i=0; i<4; i++) {
    for(int j=0; j<4; j++) {
        m[i][j] = i*j;

Decimal number regular expression, where digit after decimal is optional


clean and simple.

This uses Suffix and Prefix, RegEx features.

It directly returns true - false for IsMatch condition

Maven plugin not using Eclipse's proxy settings

Maven plugin uses a settings file where the configuration can be set. Its path is available in Eclipse at Window|Preferences|Maven|User Settings. If the file doesn't exist, create it and put on something like this:

<settings xmlns=""

After editing the file, it's just a matter of clicking on Update Settings button and it's done. I've just done it and it worked :)

IO Error: The Network Adapter could not establish the connection

In my case, I needed to specify a viahost and viauser. Worth trying if you're in a complex system. :)

Postgresql query between date ranges

Read the documentation.

I used a query like that:

    date_trunc('day',table1.date_eval) = '2015-02-09'


WHERE(date_trunc('day',table1.date_eval) >='2015-02-09'AND date_trunc('day',table1.date_eval) <'2015-02-09')    

Juanitos Ingenier.

Is there a way to get element by XPath using JavaScript in Selenium WebDriver?

In Chrome Dev Tools you can run the following:

$x("some xpath")

What is the meaning of ToString("X2")?

It formats the string as two uppercase hexadecimal characters.

In more depth, the argument "X2" is a "format string" that tells the ToString() method how it should format the string. In this case, "X2" indicates the string should be formatted in Hexadecimal.

byte.ToString() without any arguments returns the number in its natural decimal representation, with no padding.

Microsoft documents the standard numeric format strings which generally work with all primitive numeric types' ToString() methods. This same pattern is used for other types as well: for example, standard date/time format strings can be used with DateTime.ToString().

Repository Pattern Step by Step Explanation

As a summary, I would describe the wider impact of the repository pattern. It allows all of your code to use objects without having to know how the objects are persisted. All of the knowledge of persistence, including mapping from tables to objects, is safely contained in the repository.

Very often, you will find SQL queries scattered in the codebase and when you come to add a column to a table you have to search code files to try and find usages of a table. The impact of the change is far-reaching.

With the repository pattern, you would only need to change one object and one repository. The impact is very small.

Perhaps it would help to think about why you would use the repository pattern. Here are some reasons:

  • You have a single place to make changes to your data access

  • You have a single place responsible for a set of tables (usually)

  • It is easy to replace a repository with a fake implementation for testing - so you don't need to have a database available to your unit tests

There are other benefits too, for example, if you were using MySQL and wanted to switch to SQL Server - but I have never actually seen this in practice!

How to execute mongo commands through shell scripts?

Put this in a file called test.js:

db.getCollectionNames().forEach(function(collection) {

then run it with mongo myDbName test.js.

How to remove listview all items

I just clean the arraylist , try values.clear();

values = new ArrayList<String>();

ArrayAdapter <String> adapter;
adapter = new ArrayAdapter<String>(this, R.layout.list,, values); 

Target class controller does not exist - Laravel 8

Happened to me when I passing null to the middleware function

Route::middleware(null)->group(function () {
    Route::get('/some-path', [SomeController::class, 'search']);

Passing [] for no middleware works or probably just remove the middleware call if not using middleware :D

Fastest way to tell if two files have the same contents in Unix/Linux?

To quickly and safely compare any two files:

if cmp --silent -- "$FILE1" "$FILE2"; then
  echo "files contents are identical"
  echo "files differ"

It's readable, efficient, and works for any file names including "` $()

When to use .First and when to use .FirstOrDefault with LINQ?


  1. Returns first element of a sequence.
  2. It throw an error when There is no element in the result or source is null.
  3. you should use it,If more than one element is expected and you want only first element.


  1. Returns first element of a sequence, or a default value if no element is found.
  2. It throws an error Only if the source is null.
  3. you should use it, If more than one element is expected and you want only first element. Also good if result is empty.

We have an UserInfos table, which have some records as shown below. On the basis of this table below I have created example...

UserInfo Table

How to use First()

var result = dc.UserInfos.First(x => x.ID == 1);

There is only one record where ID== 1. Should return this record
ID: 1 First Name: Manish Last Name: Dubey Email: [email protected]

var result = dc.UserInfos.First(x => x.FName == "Rahul");   

There are multiple records where FName == "Rahul". First record should be return.
ID: 7 First Name: Rahul Last Name: Sharma Email: [email protected]

var result = dc.UserInfos.First(x => x.ID ==13);

There is no record with ID== 13. An error should be occur.
InvalidOperationException: Sequence contains no elements

How to Use FirstOrDefault()

var result = dc.UserInfos.FirstOrDefault(x => x.ID == 1);

There is only one record where ID== 1. Should return this record
ID: 1 First Name: Manish Last Name: Dubey Email: [email protected]

var result = dc.UserInfos.FirstOrDefault(x => x.FName == "Rahul");

There are multiple records where FName == "Rahul". First record should be return.
ID: 7 First Name: Rahul Last Name: Sharma Email: [email protected]

var result = dc.UserInfos.FirstOrDefault(x => x.ID ==13);

There is no record with ID== 13. The return value is null

Hope it will help you to understand when to use First() or FirstOrDefault().

How to pass command-line arguments to a PowerShell ps1 file

if you want to invoke ps1 scripts from cmd and pass arguments without invoking the script like

powershell.exe script.ps1 -c test
script -c test ( wont work )

you can do the following

setx PATHEXT "%PATHEXT%;.PS1;" /m
assoc .ps1=Microsoft.PowerShellScript.1
ftype Microsoft.PowerShellScript.1=powershell.exe "%1" %*

This is assuming powershell.exe is in your path

How to initialize private static members in C++?

The class declaration should be in the header file (Or in the source file if not shared).
File: foo.h

class foo
        static int i;

But the initialization should be in source file.
File: foo.cpp

int foo::i = 0;

If the initialization is in the header file then each file that includes the header file will have a definition of the static member. Thus during the link phase you will get linker errors as the code to initialize the variable will be defined in multiple source files. The initialisation of the static int i must be done outside of any function.

Note: Matt Curtis: points out that C++ allows the simplification of the above if the static member variable is of const int type (e.g. int, bool, char). You can then declare and initialize the member variable directly inside the class declaration in the header file:

class foo
        static int const i = 42;

Single vs double quotes in JSON

As said, JSON is not Python syntax. You need to use double quotes in JSON. Its creator is (in-)famous for using strict subsets of allowable syntax to ease programmer cognitive overload.

Below can fail if one of the JSON strings itself contains a single quote as pointed out by @Jiaaro. DO NOT USE. Left here as an example of what does not work.

It is really useful to know that there are no single quotes in a JSON string. Say, you copied and pasted it from a browser console/whatever. Then, you can just type

a = json.loads('very_long_json_string_pasted_here')

This might otherwise break if it used single quotes, too.

How to print a stack trace in Node.js?

Any Error object has a stack member that traps the point at which it was constructed.

var stack = new Error().stack
console.log( stack )

or more simply:

console.trace("Here I am!")

DevTools failed to load SourceMap: Could not load content for chrome-extension

Extensions without enough permission on chrome can cause these warnings, for example for React developer tools, check if the following procedure solves your problem:

  1. Right click on the extension icon.


  1. Go to extensions.
  2. Click the three-dot in the row of React developer tool.

Then choose "this can read and write site data". You should see 3 options in the list, pick one that is strict enough based on how much you trust the extension and also satisfies the extensions's needs.

Migration: Cannot add foreign key constraint

For me, the table column that my child table referenced wasn't indexed.

Schema::create('schools', function (Blueprint $table) {
    $table->integer('school_number')->index(); // The important thing is that this is indexed

Schema::create('students', function (Blueprint $table) {
      $table->foreign('schoolid')->references('school_number')->on('schools')->onDelete('set null');
      // ...

Ignore the terrible naming, it's from another terribly designed system.

How to remove leading and trailing whitespace in a MySQL field?

Please understand the use case before using this solution:

trim does not work while doing select query

This works

select replace(name , ' ','') from test;

While this doesn't

select trim(name) from test;

SQL Server 2000: How to exit a stored procedure?

Its because you have no BEGIN and END statements. You shouldn't be seeing the prints, or errors running this statement, only Statement Completed (or something like that).

TypeError: unsupported operand type(s) for -: 'str' and 'int'

For future reference Python is strongly typed. Unlike other dynamic languages, it will not automagically cast objects from one type or the other (say from str to int) so you must do this yourself. You'll like that in the long-run, trust me!

What do I need to do to get Internet Explorer 8 to accept a self signed certificate?

As everyone else has mentioned, the first task is to add the certificate to the Trusted Root Authority.

There is a custom exe (selfssl.exe) which will create a certificate and allow you to specify the Issued to: value (the URL). This means Internet explorer will validate the issued to url with the custom intranet url.

Make sure you restart Internet Explorer to refresh changes.

ReactJS Two components communicating

Oddly nobody mentioned mobx. The idea is similar to redux. If I have a piece of data that multiple components are subscribed to it, then I can use this data to drive multiple components.

WPF Label Foreground Color

I checked your XAML, it works fine - e.g. both labels have a gray foreground.
My guess is that you have some style which is affecting the way it looks...

Try moving your XAML to a brand-new window and see for yourself... Then, check if you have any themes or styles (in the Window.Resources for instance) which might be affecting the labels...

Laravel stylesheets and javascript don't load for non-base routes

in laravel 4 you just have to paste {{ URL::asset('/') }} this way:

  <link rel="stylesheet" href="{{ URL::asset('/') }}css/app.css" />.

It is the same for:

  <script language="JavaScript" src="{{ URL::asset('/') }}js/jquery.js"></script>
  <img src="{{ URL::asset('/') }}img/image.gif">

How do I escape the wildcard/asterisk character in bash?

Quoting when setting $FOO is not enough. You need to quote the variable reference as well:

me$ FOO="BAR * BAR"
me$ echo "$FOO"

How to create JSON Object using String?

If you use the gson.JsonObject you can have something like that:


String jsonString = "{'test1':'value1','test2':{'id':0,'name':'testName'}}"
JsonObject jsonObject = (JsonObject) jsonParser.parse(jsonString)

Insert an item into sorted list in Python

Hint 1: You might want to study the Python code in the bisect module.

Hint 2: Slicing can be used for list insertion:

>>> s = ['a', 'b', 'd', 'e']
>>> s[2:2] = ['c']
>>> s
['a', 'b', 'c', 'd', 'e']

DateTime.TryParse issue with dates of yyyy-dd-MM format

If you give the user the opportunity to change the date/time format, then you'll have to create a corresponding format string to use for parsing. If you know the possible date formats (i.e. the user has to select from a list), then this is much easier because you can create those format strings at compile time.

If you let the user do free-format design of the date/time format, then you'll have to create the corresponding DateTime format strings at runtime.

How to redirect a url in NGINX

Best way to do what you want is to add another server block:

server {
        #implemented by default, change if you need different ip or port
        #listen *:80 | *:8000;
        return 301 $scheme://$request_uri;

And edit your main server block server_name variable as following:


Important: New server block is the right way to do this, if is evil. You must use locations and servers instead of if if it's possible. Rewrite is sometimes evil too, so replaced it with return.

Return index of highest value in an array

Something like this should do the trick

function array_max_key($array) {
  $max_key = -1;
  $max_val = -1;

  foreach ($array as $key => $value) {
    if ($value > $max_val) {
      $max_key = $key;
      $max_val = $value;

  return $max_key;

How to check if cursor exists (open status)

This happened to me when a stored procedure running in SSMS encountered an error during the loop, while the cursor was in use to iterate over records and before the it was closed. To fix it I added extra code in the CATCH block to close the cursor if it is still open (using CURSOR_STATUS as other answers here suggest).

Creating a dynamic choice field

the problem is when you do

def __init__(self, user, *args, **kwargs):
    super(waypointForm, self).__init__(*args, **kwargs)
    self.fields['waypoints'] = forms.ChoiceField(choices=[ (, str(o)) for o in Waypoint.objects.filter(user=user)])

in a update request, the previous value will lost!

Show compose SMS view in Android

This worked for me.

public void onCreate(Bundle savedInstanceState) {
    Button btnSendSMS = (Button) findViewById(;
    btnSendSMS.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            sendSMS("5556", "Hi You got a message!");
           /*here i can send message to emulator 5556. In Real device 
            *you can change number*/

//Sends an SMS message to another device

private void sendSMS(String phoneNumber, String message) {
    SmsManager sms = SmsManager.getDefault();
    sms.sendTextMessage(phoneNumber, null, message, null, null);

You can add this line in AndroidManifest.xml

<uses-permission android:name="android.permission.SEND_SMS"/>

Take a look at this

This may be helpful for you.

Plot 3D data in R

I use the lattice package for almost everything I plot in R and it has a corresponing plot to persp called wireframe. Let data be the way Sven defined it.

wireframe(z ~ x * y, data=data)

wireframe plot

Or how about this (modification of fig 6.3 in Deepanyan Sarkar's book):

p <- wireframe(z ~ x * y, data=data)
npanel <- c(4, 2)
rotx <- c(-50, -80)
rotz <- seq(30, 300, length = npanel[1]+1)
update(p[rep(1, prod(npanel))], layout = npanel,
    panel = function(..., screen) {
        panel.wireframe(..., screen = list(z = rotz[current.column()],
                                           x = rotx[current.row()]))

Multiple wireframe plots using panel and update

Update: Plotting surfaces with OpenGL

Since this post continues to draw attention I want to add the OpenGL way to make 3-d plots too (as suggested by @tucson below). First we need to reformat the dataset from xyz-tripplets to axis vectors x and y and a matrix z.

x <- 1:5/10
y <- 1:5
z <- x %o% y
z <- z + .2*z*runif(25) - .1*z

persp3d(x, y, z, col="skyblue")


This image can be freely rotated and scaled using the mouse, or modified with additional commands, and when you are happy with it you save it using rgl.snapshot.


multiple where condition codeigniter

it's late for this answer but i think maybe still can help, i try the both methods above, using two where conditions and the method with the array, none of those work for me i did several test and the condition was never getting executed, so i did a workaround, here is my code:

public function validateLogin($email, $password){
        $password = md5($password);
        $query = $this->db->get_where("users", array("email" => $email));
        $p = $query->row_array();

        if($query->num_rows() == 1 && $password == $p['password']){  
            return $query->row();


Merge two json/javascript arrays in to one array

You can achieve this using Lodash _.merge function.

var json1 = [{id:1, name: 'xxx'}];_x000D_
var json2 = [{id:2, name: 'xyz'}];_x000D_
var merged = _.merge(_.keyBy(json1, 'id'), _.keyBy(json2, 'id'));_x000D_
var finalObj = _.values(merged);_x000D_
<script src="[email protected]/lodash.min.js"></script>

How can I get screen resolution in java?

This call will give you the information you want.

Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();

Remove attribute "checked" of checkbox

I use prop attribute for unchecked the checkbox when errors occur. You don't need to use remove property for unchecked your checkbox.

$('input#IDName').prop('checked', false);

It is working fine for me. Hope it will work for you also.

Plugin execution not covered by lifecycle configuration (JBossas 7 EAR archetype)

You need to understand the content in M2E_plugin_execution_not_covered and follow the steps mentioned below:

  • Pick org.eclipse.m2e.lifecyclemapping.defaults jar from the eclipse plugin folder
  • Extract it and open lifecycle-mapping-metadata.xml where you can find all the pluginExecutions.
  • Add the pluginExecutions of your plugins which are shown as errors with <ignore/> under <action> tags.

eg: for write-project-properties error, add this snippet under the <pluginExecutions> section of the lifecycle-mapping-metadata.xml file:

       <ignore />
  • Replace that XML file in the JAR
  • Replace the updated JAR in Eclipse's plugin folder
  • Restart Eclipse

You should see no errors in the future for any project.

How to avoid using Select in Excel VBA

Working with the .Parent feature, this example shows how setting only one myRng reference enables dynamic access to the entire environment without any .Select, .Activate, .Activecell, .ActiveWorkbook, .ActiveSheet and so on. (There isn't any generic .Child feature.)

Sub ShowParents()
    Dim myRng As Range
    Set myRng = ActiveCell
    Debug.Print myRng.Address                    ' An address of the selected cell
    Debug.Print                ' The name of sheet, where MyRng is in
    Debug.Print         ' The name of workbook, where MyRng is in
    Debug.Print  ' The name of application, where MyRng is in

    ' You may use this feature to set reference to these objects
    Dim mySh  As Worksheet
    Dim myWbk As Workbook
    Dim myApp As Application

    Set mySh = myRng.Parent
    Set myWbk = myRng.Parent.Parent
    Set myApp = myRng.Parent.Parent.Parent
    Debug.Print, mySh.Cells(10, 1).Value
    Debug.Print, myWbk.Sheets.Count
    Debug.Print, myApp.Workbooks.Count

    ' You may use dynamically addressing
    With myRng

        ' Pastes in D1 on sheet 2 in the same workbook, where the copied cell is
        .Parent.Parent.Sheets(2).Range("D1").PasteSpecial xlValues

        ' Or myWbk.Sheets(2).Range("D1").PasteSpecial xlValues

        ' We may dynamically call active application too
        .Parent.Parent.Parent.CutCopyMode = False

        ' Or myApp.CutCopyMode = False
    End With
End Sub

Apache 2.4.3 (with XAMPP 1.8.1) not starting in windows 8

I had the exact same error.

It was because i didn't run setup_xampp.bat

This is a better solution than going through config files and changing ports.

Regex for string contains?

Just don't anchor your pattern:


The above regex will check for the literal string "Test" being found somewhere within it.

How to send objects through bundle

The Parcelable interface is a good way to pass an object with an Intent.

How can I make my custom objects Parcelable? is a pretty good answer on how to use Parcelable

The official google docs also include an example

Greater than and less than in one statement

If this is really bothering you, why not write your own method isBetween(orderBean.getFiles().size(),0,5)?

Another option is to use isEmpty as it is a tad clearer:

if(!orderBean.getFiles().isEmpty() && orderBean.getFiles().size() < 5)

Install Visual Studio 2013 on Windows 7

Fake IE10 to install Visual Studio 2013

Visual Studio 2013 requires Internet Explorer 10. If you try to install it on Windows 7 with IE8 you get the following error This version of Visual Studio requires Internet Explorer 10”. The value that the VS 2013 installer checks is svcVersion in the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorerkey on 32-bit Windows and HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Internet Explorer on 64-bit Windows. Any value >= makes the installer happy.

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer]

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Internet Explorer]

How to check if a json key exists?

just before read key check it like before read

JSONObject json_obj=new JSONObject(yourjsonstr);
  //it's contain value to be read operation
  //it's not contain key club or isnull so do this operation here

isNull function definition

Returns true if this object has no mapping for name or
if it has a mapping whose value is NULL. 

official documentation below link for isNull function

Find size of Git repository

Note that, since git 1.8.3 (April, 22d 2013):

"git count-objects" learned "--human-readable" aka "-H" option to show various large numbers in Ki/Mi/GiB scaled as necessary.

That could be combined with the -v option mentioned by Jack Morrison in his answer.

git gc
git count-objects -vH

(git gc is important, as mentioned by A-B-B's answer)

Plus (still git 1.8.3), the output is more complete:

"git count-objects -v" learned to report leftover temporary packfiles and other garbage in the object store.

Adding rows to dataset

 DataSet ds = new DataSet();

 DataTable dt = new DataTable("MyTable");
 dt.Columns.Add(new DataColumn("id",typeof(int)));
 dt.Columns.Add(new DataColumn("name", typeof(string)));

 DataRow dr = dt.NewRow();
 dr["id"] = 123;
 dr["name"] = "John";

Add an index (numeric ID) column to large data frame

Using alternative dplyr package:

library("dplyr") # or library("tidyverse")

df <- df %>% mutate(id = row_number())

How do I compare two string variables in an 'if' statement in Bash?




if [ "x$s1" == "x$s2" ]
  echo match

Adding an additional string inside makes it more safe.

You could also use another notation for single-line commands:

[ "x$s1" == "x$s2" ] && echo match

Find object by its property in array of objects with AngularJS way

you can use angular's filter

in your controller:

$filter('filter')(myArray, {'id':73}) 

or in your HTML

{{ myArray | filter : {'id':73} }}

Redirect to an external URL from controller action in Spring MVC

You can do it with two ways.


@RequestMapping(value = "/redirect", method = RequestMethod.GET)
public void method(HttpServletResponse httpServletResponse) {
    httpServletResponse.setHeader("Location", projectUrl);


@RequestMapping(value = "/redirect", method = RequestMethod.GET)
public ModelAndView method() {
    return new ModelAndView("redirect:" + projectUrl);

PHP is_numeric or preg_match 0-9 validation

According to, is_numeric alows something like "+0123.45e6" or "0xFF". I think this not what you expect.

preg_match can be slow, and you can have something like 0000 or 0051.

I prefer using ctype_digit (works only with strings, it's ok with $_GET).

  $id = $_GET['id'];
  if (ctype_digit($id)) {
      echo 'ok';
  } else {
      echo 'nok';

How to fix Hibernate LazyInitializationException: failed to lazily initialize a collection of roles, could not initialize proxy - no Session

There are cases where you don't need to put @Transactional annotation to your service method, like integration testing. I was getting this org.hibernate.LazyInitializationException when testing a method that just selects from database, which did not need to be transactional. The entity class I try to load has a lazy fetch relation that caused this

@OneToMany(mappedBy = "parent", fetch = FetchType.LAZY)
private List<Item> items;

so I ended up adding the @Transactional to only to the test method.

public void verifySomethingTestSomething()  {

Input type DateTime - Value format?

This works for setting the value of the INPUT:

strftime('%Y-%m-%dT%H:%M:%S', time())

Is there a keyboard shortcut (hotkey) to open Terminal in macOS?

iTerm2 - an alternative to Terminal - has an option to use configurable system-wide hotkey to show/hide (initially set to Alt+Space, disabled by default)

Vue component event after render

updated might be what you're looking for.

how can get index & count in vuejs

you can just add 1

<li v-for="(catalog, itemObjKey) in catalogs">this index : {{itemObjKey + 1}}</li>

to get the length of an array/objects

{{ catalogs.length }}

What is Java String interning?


JLS 7 3.10.5 defines it and gives a practical example:

Moreover, a string literal always refers to the same instance of class String. This is because string literals - or, more generally, strings that are the values of constant expressions (§15.28) - are "interned" so as to share unique instances, using the method String.intern.

Example 3.10.5-1. String Literals

The program consisting of the compilation unit (§7.3):

package testPackage;
class Test {
    public static void main(String[] args) {
        String hello = "Hello", lo = "lo";
        System.out.print((hello == "Hello") + " ");
        System.out.print((Other.hello == hello) + " ");
        System.out.print((other.Other.hello == hello) + " ");
        System.out.print((hello == ("Hel"+"lo")) + " ");
        System.out.print((hello == ("Hel"+lo)) + " ");
        System.out.println(hello == ("Hel"+lo).intern());
class Other { static String hello = "Hello"; }

and the compilation unit:

package other;
public class Other { public static String hello = "Hello"; }

produces the output:

true true true true false true


JVMS 7 5.1 says says that interning is implemented magically and efficiently with a dedicated CONSTANT_String_info struct (unlike most other objects which have more generic representations):

A string literal is a reference to an instance of class String, and is derived from a CONSTANT_String_info structure (§4.4.3) in the binary representation of a class or interface. The CONSTANT_String_info structure gives the sequence of Unicode code points constituting the string literal.

The Java programming language requires that identical string literals (that is, literals that contain the same sequence of code points) must refer to the same instance of class String (JLS §3.10.5). In addition, if the method String.intern is called on any string, the result is a reference to the same class instance that would be returned if that string appeared as a literal. Thus, the following expression must have the value true:

("a" + "b" + "c").intern() == "abc"

To derive a string literal, the Java Virtual Machine examines the sequence of code points given by the CONSTANT_String_info structure.

  • If the method String.intern has previously been called on an instance of class String containing a sequence of Unicode code points identical to that given by the CONSTANT_String_info structure, then the result of string literal derivation is a reference to that same instance of class String.

  • Otherwise, a new instance of class String is created containing the sequence of Unicode code points given by the CONSTANT_String_info structure; a reference to that class instance is the result of string literal derivation. Finally, the intern method of the new String instance is invoked.


Let's decompile some OpenJDK 7 bytecode to see interning in action.

If we decompile:

public class StringPool {
    public static void main(String[] args) {
        String a = "abc";
        String b = "abc";
        String c = new String("abc");
        System.out.println(a == c);

we have on the constant pool:

#2 = String             #32   // abc
#32 = Utf8               abc

and main:

 0: ldc           #2          // String abc
 2: astore_1
 3: ldc           #2          // String abc
 5: astore_2
 6: new           #3          // class java/lang/String
 9: dup
10: ldc           #2          // String abc
12: invokespecial #4          // Method java/lang/String."<init>":(Ljava/lang/String;)V
15: astore_3
16: getstatic     #5          // Field java/lang/System.out:Ljava/io/PrintStream;
19: aload_1
20: invokevirtual #6          // Method java/io/PrintStream.println:(Ljava/lang/String;)V
23: getstatic     #5          // Field java/lang/System.out:Ljava/io/PrintStream;
26: aload_2
27: invokevirtual #6          // Method java/io/PrintStream.println:(Ljava/lang/String;)V
30: getstatic     #5          // Field java/lang/System.out:Ljava/io/PrintStream;
33: aload_1
34: aload_3
35: if_acmpne     42
38: iconst_1
39: goto          43
42: iconst_0
43: invokevirtual #7          // Method java/io/PrintStream.println:(Z)V

Note how:

  • 0 and 3: the same ldc #2 constant is loaded (the literals)
  • 12: a new string instance is created (with #2 as argument)
  • 35: a and c are compared as regular objects with if_acmpne

The representation of constant strings is quite magic on the bytecode:

and the JVMS quote above seems to say that whenever the Utf8 pointed to is the same, then identical instances are loaded by ldc.

I have done similar tests for fields, and:

  • static final String s = "abc" points to the constant table through the ConstantValue Attribute
  • non-final fields don't have that attribute, but can still be initialized with ldc

Conclusion: there is direct bytecode support for the string pool, and the memory representation is efficient.

Bonus: compare that to the Integer pool, which does not have direct bytecode support (i.e. no CONSTANT_String_info analogue).

What is the difference between Scope_Identity(), Identity(), @@Identity, and Ident_Current()?

To clarify the problem with @@Identity:

For instance, if you insert a table and that table has triggers doing inserts, @@Identity will return the id from the insert in the trigger (a log_id or something), while scope_identity() will return the id from the insert in the original table.

So if you don't have any triggers, scope_identity() and @@identity will return the same value. If you have triggers, you need to think about what value you'd like.

HTML Best Practices: Should I use &rsquo; or the special keyboard shortcut?

I don't think that one is better than the other in general; it depends on how you intend to use it.

  • If you want to store it in a DB column that has a charset/collation that does not support the right single quote character, you may run into storing it as the multi-byte character instead of 7-bit ASCII (&rsquo;).
  • If you are displaying it on an html element that specifies a charset that does not support it, it may not display in either case.
  • If many developers are going to be editing/viewing this file with editors/keyboards that do not support properly typing or displaying the character, you may want to use the entity
  • If you need to convert the file between various character encodings or formats, you may want to use the entity
  • If your HTML code may escape entities improperly, you may want to use the character.

In general I would lean more towards using the character because as you point out it is easier to read and type.

Bypass invalid SSL certificate errors when calling web services in .Net

Alternatively you can register a call back delegate which ignores the certification error:

ServicePointManager.ServerCertificateValidationCallback = MyCertHandler;

static bool MyCertHandler(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors error)
// Ignore errors
return true;

How permission can be checked at runtime without throwing SecurityException?

You should check for permissions in the following way (as described here Android permissions):

int result = ContextCompat.checkSelfPermission(getContext(), Manifest.permission.READ_PHONE_STATE);

then, compare your result to either:

result == PackageManager.PERMISSION_DENIED


result == PackageManager.PERMISSION_GRANTED

set the iframe height automatically

If you a framework like Bootstrap you can make any iframe video responsive by using this snippet:

<div class="embed-responsive embed-responsive-16by9">
    <iframe class="embed-responsive-item" src="vid.mp4" allowfullscreen></iframe>

Is there a free GUI management tool for Oracle Database Express?

Try odbTools at - it is free.

odbTools is set of integrated GUI tools to manage, administer, monitor and tune the Oracle database.

How to start jenkins on different port rather than 8080 using command prompt in Windows?

Use the following command at command prompt:

java -jar jenkins.war --httpPort=9090

If you want to use https use the following command:

java -jar jenkins.war --httpsPort=9090

Details are here

Return anonymous type results?

BreedId in the Dog table is obviously a foreign key to the corresponding row in the Breed table. If you've got your database set up properly, LINQ to SQL should automatically create an association between the two tables. The resulting Dog class will have a Breed property, and the Breed class should have a Dogs collection. Setting it up this way, you can still return IEnumerable<Dog>, which is an object that includes the breed property. The only caveat is that you need to preload the breed object along with dog objects in the query so they can be accessed after the data context has been disposed, and (as another poster has suggested) execute a method on the collection that will cause the query to be performed immediately (ToArray in this case):

public IEnumerable<Dog> GetDogs()
    using (var db = new DogDataContext(ConnectString))
        db.LoadOptions.LoadWith<Dog>(i => i.Breed);
        return db.Dogs.ToArray();


It is then trivial to access the breed for each dog:

foreach (var dog in GetDogs())
    Console.WriteLine("Dog's Name: {0}", dog.Name);
    Console.WriteLine("Dog's Breed: {0}", dog.Breed.Name);        

Parsing a comma-delimited std::string

Lots of pretty terrible answers here so I'll add mine (including test program):

#include <string>
#include <iostream>
#include <cstddef>

template<typename StringFunction>
void splitString(const std::string &str, char delimiter, StringFunction f) {
  std::size_t from = 0;
  for (std::size_t i = 0; i < str.size(); ++i) {
    if (str[i] == delimiter) {
      f(str, from, i);
      from = i + 1;
  if (from <= str.size())
    f(str, from, str.size());

int main(int argc, char* argv[]) {
    if (argc != 2)
        return 1;

    splitString(argv[1], ',', [](const std::string &s, std::size_t from, std::size_t to) {
        std::cout << "`" << s.substr(from, to - from) << "`\n";

    return 0;

Nice properties:

  • No dependencies (e.g. boost)
  • Not an insane one-liner
  • Easy to understand (I hope)
  • Handles spaces perfectly fine
  • Doesn't allocate splits if you don't want to, e.g. you can process them with a lambda as shown.
  • Doesn't add characters one at a time - should be fast.
  • If using C++17 you could change it to use a std::stringview and then it won't do any allocations and should be extremely fast.

Some design choices you may wish to change:

  • Empty entries are not ignored.
  • An empty string will call f() once.

Example inputs and outputs:

""      ->   {""}
","     ->   {"", ""}
"1,"    ->   {"1", ""}
"1"     ->   {"1"}
" "     ->   {" "}
"1, 2," ->   {"1", " 2", ""}
" ,, "  ->   {" ", "", " "}

How can I remove the string "\n" from within a Ruby string?

When you want to remove a string, rather than replace it you can use String#delete (or its mutator equivalent String#delete!), e.g.:

x = "foo\nfoo"

x now equals "foofoo"

In this specific case String#delete is more readable than gsub since you are not actually replacing the string with anything.

What is external linkage and internal linkage?

In C++

Any variable at file scope and that is not nested inside a class or function, is visible throughout all translation units in a program. This is called external linkage because at link time the name is visible to the linker everywhere, external to that translation unit.

Global variables and ordinary functions have external linkage.

Static object or function name at file scope is local to translation unit. That is called as Internal Linkage

Linkage refers only to elements that have addresses at link/load time; thus, class declarations and local variables have no linkage.

Count(*) vs Count(1) - SQL Server

If you run the following in SQL Server, you'll notice that COUNT(1) is evaluated as COUNT(*) anyway. So it appears that there is no difference, and also that COUNT(*) is the expression most native to the query optimizer:


FROM <table>


What are the possible values of the Hibernate configuration and what do they do

validate: It validates the schema and makes no changes to the DB.
Assume you have added a new column in the mapping file and perform the insert operation, it will throw an Exception "missing the XYZ column" because the existing schema is different than the object you are going to insert. If you alter the table by adding that new column manually then perform the Insert operation then it will definitely insert all columns along with the new column to the Table. Means it doesn't make any changes/alters the existing schema/table.

update: it alters the existing table in the database when you perform operation. You can add or remove columns with this option of hbm2ddl. But if you are going to add a new column that is 'NOT NULL' then it will ignore adding that particular column to the DB. Because the Table must be empty if you want to add a 'NOT NULL' column to the existing table.

How make background image on newsletter in outlook?

Powerful tool for "Bulletproof Email Background Images" (VML for Outlook 2007/2010/2013, and HTML/CSS for Outlook 2000/2003, Gmail, Hotmail...)

as an exemple :

    <div style="background-color:#f6f6f6;">
  <!--[if gte mso 9]>
  <v:background xmlns:v="urn:schemas-microsoft-com:vml" fill="t">
    <v:fill type="tile" src="" color="#f6f6f6"/>
  <table height="100%" width="100%" cellpadding="0" cellspacing="0" border="0">
      <td valign="top" align="left" background="">

in order to have the specified background image to Full email body.

This link help to use the Vector Markup Language (VML)

How to get the path of the batch script in Windows?

You can use following script to get the path without trailing "\"

for %%i in ("%~dp0.") do SET "mypath=%%~fi"

How to set a background image in Xcode using swift?

Swift 5.3 in XCode 12.2 Playgrounds

Place the cursor wherever in the code the #insertLiteral would have been in earlier versions. Select from the top-menu Editor->Insert Image Literal... and navigate to the file. Click Open.

The file is added to a playground Resource folder and will then appear when the playground is run in whichever view it was positioned when selected.

If a file is already in the playground Bundle, e.g. in /Resources, it can be dragged directly to the required position in the code (where it will be represented by an icon).

cf. Apple help docs give details of this and how to place other colour and file literals.

What is the difference between functional and non-functional requirements?

I think functional requirement is from client to developer side that is regarding functionality to the user by the software and non-functional requirement is from developer to client i.e. the requirement is not given by client but it is provided by developer to run the system smoothly e.g. safety, security, flexibility, scalability, availability, etc.

In HTML5, should the main navigation be inside or outside the <header> element?

To expand on what @JoshuaMaddox said, in the MDN Learning Area, under the "Introduction to HTML" section, the Document and website structure sub-section says (bold/emphasis is by me):


Usually a big strip across the top with a big heading and/or logo. This is where the main common information about a website usually stays from one webpage to another.

Navigation bar

Links to the site's main sections; usually represented by menu buttons, links, or tabs. Like the header, this content usually remains consistent from one webpage to another — having an inconsistent navigation on your website will just lead to confused, frustrated users. Many web designers consider the navigation bar to be part of the header rather than a individual component, but that's not a requirement; in fact some also argue that having the two separate is better for accessibility, as screen readers can read the two features better if they are separate.

How to change column datatype from character to numeric in PostgreSQL 8.4

Step 1: Add new column with integer or numeric as per your requirement

Step 2: Populate data from varchar column to numeric column

Step 3: drop varchar column

Step 4: change new numeric column name as per old varchar column

React "after render" code?

I am not going to pretend I know why this particular function works, however window.getComputedStyle works 100% of the time for me whenever I need to access DOM elements with a Ref in a useEffect — I can only presume it will work with componentDidMount as well.

I put it at the top of the code in a useEffect and it appears as if it forces the effect to wait for the elements to be painted before it continues with the next line of code, but without any noticeable delay such as using a setTimeout or an async sleep function. Without this, the Ref element returns as undefined when I try to access it.

const ref = useRef(null);

    // Next lines of code to get element and do something after getComputedStyle().

return(<div ref={ref}></div>);

how to iterate through dictionary in a dictionary in django template?

Lets say your data is -

data = {'a': [ [1, 2] ], 'b': [ [3, 4] ],'c':[ [5,6]] }

You can use the data.items() method to get the dictionary elements. Note, in django templates we do NOT put (). Also some users mentioned values[0] does not work, if that is the case then try values.items.


    {% for key, values in data.items %}
        {% for v in values[0] %}
        {% endfor %}
    {% endfor %}

Am pretty sure you can extend this logic to your specific dict.

To iterate over dict keys in a sorted order - First we sort in python then iterate & render in django template.

return render_to_response('some_page.html', {'data': sorted(data.items())})

In template file:

{% for key, value in data %}
        <td> Key: {{ key }} </td> 
        <td> Value: {{ value }} </td>
{% endfor %}

how to display employee names starting with a and then b in sql

If you're asking about alphabetical order the syntax is:

SELECT * FROM table ORDER BY column

the best example I can give without knowing your table and field names:

SELECT * FROM employees ORDER BY name

git add only modified changes and ignore untracked files

git commit -a -m "message"

-a : Includes all currently changed/deleted files in this commit. Keep in mind, however, that untracked (new) files are not included.

-m : Sets the commit's message

Error: EACCES: permission denied, access '/usr/local/lib/node_modules'

Simply you can change the owner or just use sudo before you command like this

sudo chown -R [owner]:[owner] /usr/local/lib/node_modules (change owner)


sudo npm install -g json-server

that's it.

How do I check if file exists in jQuery or pure JavaScript?

I wanted a function that would return a boolean, I encountered problems related to closure and asynchronicity. I solved this way:

checkFileExistence= function (file){
        .done(function() {
        .fail(function() {

Python "\n" tag extra line

use join(), don't rely on the , for formatting, and also print automatically puts the cursor on a newline every time, so no need of adding another '\n' in your print.

In [24]: for x in board:
    print " ".join(map(str,x))
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 3 2 1 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0

Pressing Ctrl + A in Selenium WebDriver

Since Ctrl+A maps to ASCII code value 1 (Ctrl+B to 2, up to, Ctrl+Z to 26).


using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using OpenQA.Selenium;
using OpenQA.Selenium.IE;
using OpenQA.Selenium.Support.UI;
using OpenQA.Selenium.Interactions;
using OpenQA.Selenium.Internal;
using OpenQA.Selenium.Remote;

namespace SeleniumHqTest
    class Test
            IWebDriver driver = new InternetExplorerDriver();
            IWebElement el = driver.FindElement(By.Id("an_element_id"));
            char c = '\u0001'; // ASCII code 1 for Ctrl-A

How to determine total number of open/active connections in ms sql server 2005

Use this to get an accurate count for each connection pool (assuming each user/host process uses the same connection string)

DB_NAME(dbid) as DBName, 
COUNT(dbid) as NumberOfConnections,
loginame as LoginName, hostname, hostprocess
sys.sysprocesses with (nolock)
dbid > 0
dbid, loginame, hostname, hostprocess

How to get a DOM Element from a JQuery Selector

If you need to interact directly with the DOM element, why not just use document.getElementById since, if you are trying to interact with a specific element you will probably know the id, as assuming that the classname is on only one element or some other option tends to be risky.

But, I tend to agree with the others, that in most cases you should learn to do what you need using what jQuery gives you, as it is very flexible.

UPDATE: Based on a comment: Here is a post with a nice explanation:[email protected]/msg04461.html

$(this).attr("checked") ? $(this).val() : 0

This will return the value if it's checked, or 0 if it's not.

$(this).val() is just reaching into the dom and getting the attribute "value" of the element, whether or not it's checked.

What exactly are DLL files, and how do they work?

DLL files contain an Export Table which is a list of symbols which can be looked up by the calling program. The symbols are typically functions with the C calling convention (__stcall). The export table also contains the address of the function.

With this information, the calling program can then call the functions within the DLL even though it did not have access to the DLL at compile time.

Introducing Dynamic Link Libraries has some more information.

How to set up default schema name in JPA configuration?

Just to save time of people who come to the post (like me, who looking for Spring config type and want you schema name be set by an external source (property file)). The configuration will work for you is

<bean id="domainEntityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="persistenceUnitName" value="JiraManager"/>
    <property name="dataSource" ref="domainDataSource"/>
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
            <property name="generateDdl" value="false"/>
            <property name="showSql" value="false"/>
            <property name="databasePlatform" value="${hibernate.dialect}"/>
    <property name="jpaProperties">
            <prop key="">none</prop>
            <prop key="hibernate.default_schema">${yourSchema}</prop>


Ps : For the, you could look in the post Hibernate possible values and what they do? I have used to set create-update,because it is convenient. However, in production, I think it is better to take control of the ddl, so I take whatever ddl generate first time, save it, rather than let it automatically create and update.

500 internal server error, how to debug

Try writing all the errors to a file.

error_reporting(-1); // reports all errors
ini_set("display_errors", "1"); // shows all errors
ini_set("log_errors", 1);
ini_set("error_log", "/tmp/php-error.log");

Something like that.

MySQL duplicate entry error even though there is no duplicate entry

In case anyone else finds this thread with my problem -- I was using an "integer" column type in MySQL. The row I was attempting to insert had a primary key with a value larger than allowed by integer. Switching to "bigint" fixed the problem.

Java - Opposite of .contains (does not contain)


if (inventory.contains("bread") && !inventory.contains("water"))


if (inventory.contains("bread")) {
    if (!inventory.contains("water")) {
        // do something here

What does .class mean in Java?

That means a Class with a type of anything (unknown).

You should read java generics tutorial to get to understand it better

PostgreSQL - max number of parameters in "IN" clause?

There is no limit to the number of elements that you are passing to IN clause. If there are more elements it will consider it as array and then for each scan in the database it will check if it is contained in the array or not. This approach is not so scalable. Instead of using IN clause try using INNER JOIN with temp table. Refer for more info. Using INNER JOIN scales well as query optimizer can make use of hash join and other optimization. Whereas with IN clause there is no way for the optimizer to optimize the query. I have noticed speedup of at least 2x with this change.

How to use a variable of one method in another method?

You can't. Variables defined inside a method are local to that method.

If you want to share variables between methods, then you'll need to specify them as member variables of the class. Alternatively, you can pass them from one method to another as arguments (this isn't always applicable).

Looks like you're using instance methods instead of static ones.

If you don't want to create an object, you should declare all your methods static, so something like

private static void methodName(Argument args...)

If you want a variable to be accessible by all these methods, you should initialise it outside the methods and to limit its scope, declare it private.

private static int[][] array = new int[3][5];

Global variables are usually looked down upon (especially for situations like your one) because in a large-scale program they can wreak havoc, so making it private will prevent some problems at the least.

Also, I'll say the usual: You should try to keep your code a bit tidy. Use descriptive class, method and variable names and keep your code neat (with proper indentation, linebreaks etc.) and consistent.

Here's a final (shortened) example of what your code should be like:

public class Test3 {
    //Use this array in your methods
    private static int[][] scores = new int[3][5];

    /* Rather than just "Scores" name it so people know what
     * to expect
    private static void createScores() {
    //Other methods...

    /* Since you're now using static methods, you don't 
     * have to initialise an object and call its methods.
    public static void main(String[] args){
        MD();   //Don't know what these do
        sumD(); //so I'll leave them.

Ideally, since you're using an array, you would create the array in the main method and pass it as an argument across each method, but explaining how that works is probably a whole new question on its own so I'll leave it at that.

SQL Add foreign key to existing column

If the table has already been created:

First do:

ALTER TABLE `table1_name` ADD UNIQUE( `column_name`);


ALTER TABLE `table1_name` ADD FOREIGN KEY (`column_name`) REFERENCES `table2_name`(`column_name`);

What is copy-on-write?

I was going to write up my own explanation but this Wikipedia article pretty much sums it up.

Here is the basic concept:

Copy-on-write (sometimes referred to as "COW") is an optimization strategy used in computer programming. The fundamental idea is that if multiple callers ask for resources which are initially indistinguishable, you can give them pointers to the same resource. This function can be maintained until a caller tries to modify its "copy" of the resource, at which point a true private copy is created to prevent the changes becoming visible to everyone else. All of this happens transparently to the callers. The primary advantage is that if a caller never makes any modifications, no private copy need ever be created.

Also here is an application of a common use of COW:

The COW concept is also used in maintenance of instant snapshot on database servers like Microsoft SQL Server 2005. Instant snapshots preserve a static view of a database by storing a pre-modification copy of data when underlaying data are updated. Instant snapshots are used for testing uses or moment-dependent reports and should not be used to replace backups.

How to create a date object from string in javascript

Always, for any issue regarding the JavaScript spec in practical, I will highly recommend the Mozilla Developer Network, and their JavaScript reference.

As it states in the topic of the Date object about the argument variant you use:

new Date(year, month, day [, hour, minute, second, millisecond ])

And about the months parameter:

month Integer value representing the month, beginning with 0 for January to 11 for December.

Clearly, then, you should use the month number 10 for November.

P.S.: The reason why I recommend the MDN is the correctness, good explanation of things, examples, and browser compatibility chart.

ACCESS_FINE_LOCATION AndroidManifest Permissions Not Being Granted

just remove s from the permission you are using sss you have to use ss

How to shut down the computer from C#

Taken from: a Geekpedia post

This method uses WMI to shutdown windows.

You'll need to add a reference to System.Management to your project to use this.

using System.Management;

void Shutdown()
    ManagementBaseObject mboShutdown = null;
    ManagementClass mcWin32 = new ManagementClass("Win32_OperatingSystem");

    // You can't shutdown without security privileges
    mcWin32.Scope.Options.EnablePrivileges = true;
    ManagementBaseObject mboShutdownParams =

     // Flag 1 means we want to shut down the system. Use "2" to reboot.
    mboShutdownParams["Flags"] = "1";
    mboShutdownParams["Reserved"] = "0";
    foreach (ManagementObject manObj in mcWin32.GetInstances())
        mboShutdown = manObj.InvokeMethod("Win32Shutdown", 
                                       mboShutdownParams, null);

Installation failed with message Invalid File

  1. Invalidate cache/restart
  2. Clean Project
  3. Rebuild Project
  4. Run your app / Build APK

These steps are enough to solve most of the problems related to Gradle build in any way. These steps helped me solve this problem too.

Laravel Request::all() Should Not Be Called Statically

The facade is another Request class, access it with the full path:

$input = \Request::all();

From laravel 5 you can also access it through the request() function:

$input = request()->all();

Installed Ruby 1.9.3 with RVM but command line doesn't show ruby -v

You have broken version of RVM. Ubuntu does something to RVM that produces lots of errors, the only safe way of fixing for now is to:

sudo apt-get --purge remove ruby-rvm
sudo rm -rf /usr/share/ruby-rvm /etc/rvmrc /etc/profile.d/

open new terminal and validate environment is clean from old RVM settings (should be no output):

env | grep rvm

if there was output, try to open new terminal, if it does not help then restart your computer.

install RVM:

\curl -L | 
  bash -s stable --ruby --autolibs=enable --auto-dotfiles

If you find you need some hand-holding, take a look at Installing Ruby on Ubuntu 12.04, which gives a bit more explanation.

int to string in MySQL

If you have a column called "col1" which is int, you cast it to String like this:


e.g. this allows you to check an int value is containing another value (here 9) like this:

CONVERT(col1,char) LIKE '%9%'

What is the difference between . (dot) and $ (dollar sign)?

They have different types and different definitions:

infixr 9 .
(.) :: (b -> c) -> (a -> b) -> (a -> c)
(f . g) x = f (g x)

infixr 0 $
($) :: (a -> b) -> a -> b
f $ x = f x

($) is intended to replace normal function application but at a different precedence to help avoid parentheses. (.) is for composing two functions together to make a new function.

In some cases they are interchangeable, but this is not true in general. The typical example where they are is:

f $ g $ h $ x


f . g . h $ x

In other words in a chain of $s, all but the final one can be replaced by .

In Postgresql, force unique on combination of two columns

Create unique constraint that two numbers together CANNOT together be repeated:

ADD UNIQUE (col1, col2)

how to empty recyclebin through command prompt?

I prefer recycle.exe from Frank P. Westlake. It provides a nice before and after status. (I've been using Frank's various utilities for well over ten years..)

C:\> recycle.exe /E /F
Recycle Bin: ALL
    Recycle Bin C:  44 items, 42,613,970 bytes.
    Recycle Bin D:   0 items, 0 bytes.
            Total:  44 items, 42,613,970 bytes.

Emptying Recycle Bin: ALL
    Recycle Bin C:   0 items, 0 bytes.
    Recycle Bin D:   0 items, 0 bytes.
            Total:   0 items, 0 bytes.

It also has many more uses and options (output listed is from /?).

Recycle all files and folders in C:\TEMP:

List all DOC files which were recycled from any directory on the C: drive:

Restore all DOC files which were recycled from any directory on the C: drive:

Restore C:\temp\junk.txt to C:\docs\resume.txt:
  RECYCLE /U "C:\temp\junk.txt" "C:\docs\resume.txt"

Rename in place C:\etc\config.cfg to C:\archive\config.2007.cfg:
  RECYCLE /R "C:\etc\config.cfg" "C:\archive\config.2007.cfg"

How to check if a file exists in Documents folder?

check if file exist in side the document/catchimage path :

NSString *stringPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)objectAtIndex:0];
NSString *tempName = [NSString stringWithFormat:@"%@/catchimage/%@.png",stringPath,@"file name"];
if([[NSFileManager defaultManager] fileExistsAtPath:temName]){
    // ur code here
} else {
    // ur code here** 

How can I display a tooltip on an HTML "option" tag?

I don't believe that you can achieve this functionality with standard <select> element.

What i would suggest is to use such way.

The basic version of it won't take too much space and you can easily bind mouseover events to sub items to show a nice tooltip.

Hope this helps, Sinan.

Is it possible to select the last n items with nth-child?

If you are using jQuery in your project, or are willing to include it you can call nth-last-child through its selector API (this is this simulated it will cross browser). Here is a link to an nth-last-child plugin. If you took this method of targeting the elements you were interested in:

$('ul li:nth-last-child(1)').addClass('last');

And then style again the last class instead of the nth-child or nth-last-child pseudo selectors, you will have a much more consistent cross browser experience.

How do I print the content of httprequest request?

Rewrite @Juned Ahsan solution via stream in one line (headers are treated the same way):

public static String printRequest(HttpServletRequest req) {
    String params =
            ((Iterable<String>) () -> req.getParameterNames().asIterator()).spliterator(), false)
            .map(pName -> pName + '=' + req.getParameter(pName))
    return req.getRequestURI() + '?' + params;

See also how to convert an iterator to a stream solution.

Parsing JSON giving "unexpected token o" error

Using JSON.stringify(data);:

    url: ...
        JSON.stringify(data); //to string
        alert(data.you_value); //to view you pop up

Creating a batch file, for simple javac and java command execution

Create a plain text file (using notepad) and type the exact line you would use to run your Java file with the command prompt. Then change the extension to .bat and you're done.

Double clicking on this file would run your java program.

I reccommend one file for javac, one for java so you can troubleshoot if anything is wrong.

  • Make sure java is in your path, too.. IE typing java in a Dos windows when in your java workspace should bring up the java version message. If java is not in your path the batch file won't work unless you use absolut path to the java binary.

How do I create a pause/wait function using Qt?

Since you're trying to "test some class code," I'd really recommend learning to use QTestLib. It provides a QTest namespace and a QtTest module that contain a number of useful functions and objects, including QSignalSpy that you can use to verify that certain signals are emitted.

Since you will eventually be integrating with a full GUI, using QTestLib and testing without sleeping or waiting will give you a more accurate test -- one that better represents the true usage patterns. But, should you choose not to go that route, you could use QTestLib::qSleep to do what you've requested.

Since you just need a pause between starting your pump and shutting it down, you could easily use a single shot timer:

class PumpTest: public QObject {
    Pump &pump;
    PumpTest(Pump &pump):pump(pump) {};
public slots:
    void start() { pump.startpump(); }
    void stop() { pump.stoppump(); }
    void stopAndShutdown() {
    void test() {
        QTimer::singleShot(1000, this, SLOT(stopAndShutdown));

int main(int argc, char* argv[]) {
    QCoreApplication app(argc, argv);
    Pump p;
    PumpTest t(p);
    return app.exec();

But qSleep() would definitely be easier if all you're interested in is verifying a couple of things on the command line.

EDIT: Based on the comment, here's the required usage patterns.

First, you need to edit your .pro file to include qtestlib:

CONFIG += qtestlib

Second, you need to include the necessary files:

  • For the QTest namespace (which includes qSleep): #include <QTest>
  • For all the items in the QtTest module: #include <QtTest>. This is functionally equivalent to adding an include for each item that exists within the namespace.

I want to multiply two columns in a pandas DataFrame and add the result into a new column

I think an elegant solution is to use the where method (also see the API docs):

In [37]: values = df.Prices * df.Amount

In [38]: df['Values'] = values.where(df.Action == 'Sell', other=-values)

In [39]: df
   Prices  Amount Action  Values
0       3      57   Sell     171
1      89      42   Sell    3738
2      45      70    Buy   -3150
3       6      43   Sell     258
4      60      47   Sell    2820
5      19      16    Buy    -304
6      56      89   Sell    4984
7       3      28    Buy     -84
8      56      69   Sell    3864
9      90      49    Buy   -4410

Further more this should be the fastest solution.

how to check the jdk version used to compile a .class file

You're looking for this on the command line (for a class called MyClass):

On Unix/Linux:

javap -verbose MyClass | grep "major"

On Windows:

javap -verbose MyClass | findstr "major"

You want the major version from the results. Here are some example values:

  • Java 1.2 uses major version 46
  • Java 1.3 uses major version 47
  • Java 1.4 uses major version 48
  • Java 5 uses major version 49
  • Java 6 uses major version 50
  • Java 7 uses major version 51
  • Java 8 uses major version 52
  • Java 9 uses major version 53
  • Java 10 uses major version 54
  • Java 11 uses major version 55

How do I install boto?

If you're on a mac, by far the simplest way to install is to use easy_install

sudo easy_install boto3

updating Google play services in Emulator

My answer is not to update the Google play service but work around. Get the play service version of the emulator by using the following code

getPackageManager().getPackageInfo("", 0 ).versionName);

For example if the value is "9.8.79" then use the nearest lesser version available'

This will resolve your problem. Get the release history from

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

The Saxon documentation, though a little unclear, seems to suggest that the JAXP XPath API will return false when evaluating an XPath expression if no matching nodes are found.

This IBM article mentions a return value of null when no nodes are matched.

You might need to play around with the return types a bit based on this API, but the basic idea is that you just run a normal XPath and check whether the result is a node / false / null / etc.

XPathFactory xpathFactory = XPathFactory.newInstance(NamespaceConstant.OBJECT_MODEL_SAXON);
XPath xpath = xpathFactory.newXPath();
XPathExpression expr = xpath.compile("/Consumers/Consumer/DataSources/Credit/CreditReport/AttachedXml");
Object result = expr.evaluate(doc, XPathConstants.NODE);

if ( result == null ) {
    // do something

How can I display a list view in an Android Alert Dialog?

You can use a custom dialog.

Custom dialog layout. list.xml

<?xml version="1.0" encoding="utf-8"?>

In your activity

Dialog dialog = new Dialog(Activity.this);

ListView lv = (ListView ) dialog.findViewById(;


Using alertdialog

String names[] ={"A","B","C","D"};
AlertDialog.Builder alertDialog = new AlertDialog.Builder(MainActivity.this);
LayoutInflater inflater = getLayoutInflater();
View convertView = (View) inflater.inflate(R.layout.custom, null);
ListView lv = (ListView) convertView.findViewById(;
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,names);


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



enter image description here

Javascript wait() function

You shouldn't edit it, you should completely scrap it.

Any attempt to make execution stop for a certain amount of time will lock up the browser and switch it to a Not Responding state. The only thing you can do is use setTimeout correctly.

Creating Accordion Table with Bootstrap

In the accepted answer you get annoying spacing between the visible rows when the expandable row is hidden. You can get rid of that by adding this to css:

.collapse-row.collapsed + tr {
     display: none;

'+' is adjacent sibling selector, so if you want your expandable row to be the next row, this selects the next tr following tr named collapse-row.

Here is updated fiddle:

What is the official name for a credit card's 3 digit code?

It's got a number of names. Most likely you've heard it as either Card Security Code (CSC) or Card Verification Value (CVV).

Card Security Code

How to prevent favicon.ico requests?

if you use nginx

# skip favicon.ico
location = /favicon.ico {
    access_log off;
    return 204;

Abstract methods in Java

If you use the java keyword abstract you cannot provide an implementation.

Sometimes this idea comes from having a background in C++ and mistaking the virtual keyword in C++ as being "almost the same" as the abstract keyword in Java.

In C++ virtual indicates that a method can be overridden and polymorphism will follow, but abstract in Java is not the same thing. In Java abstract is more like a pure virtual method, or one where the implementation must be provided by a subclass. Since Java supports polymorphism without the need to declare it, all methods are virtual from a C++ point of view. So if you want to provide a method that might be overridden, just write it as a "normal" method.

Now to protect a method from being overridden, Java uses the keyword final in coordination with the method declaration to indicate that subclasses cannot override the method.

How to add rows dynamically into table layout

Here's technique I figured out after a bit of trial and error that allows you to preserve your XML styles and avoid the issues of using a <merge/> (i.e. inflate() requires a merge to attach to root, and returns the root node). No runtime new TableRow()s or new TextView()s required.


Note: Here CheckBalanceActivity is some sample Activity class

TableLayout table = (TableLayout)CheckBalanceActivity.this.findViewById(;
for(ResourceBalance b : xmlDoc.balance_info)
    // Inflate your row "template" and fill out the fields.
    TableRow row = (TableRow)LayoutInflater.from(CheckBalanceActivity.this).inflate(R.layout.attrib_row, null);
table.requestLayout();     // Not sure if this is needed.


<?xml version="1.0" encoding="utf-8"?>
<TableRow style="@style/PlanAttribute"  xmlns:android="">

How to load my app from Eclipse to my Android phone instead of AVD

First of all, Enable USB debugging on your device.

On most devices running Android 3.2 or older, you can find the option under Settings > Applications > Development.

On Android 4.0 and newer, it's in Settings > Developer options.

In eclipse go to Run Configuration and select Always prompt to pick deviceenter image description here

ld: framework not found Pods

[Xcode 11.2.1]

For me it was different app target version in Podfile(platform :ios, '11.0') and in Xcode project file Xcode Deployment info.

It causing Archiving job fail in CI pipeline.

Matching both value fixed an issue! Hope this help anyone.

How to loop backwards in python?

To reverse a string without using reversed or [::-1], try something like:

def reverse(text):
    # Container for reversed string

    # store the length of the string to be reversed
    # account for indexes starting at 0
    length = len(text)-1

    # loop through the string in reverse and append each character
    # deprecate the length index
    while length>=0:
        txet += "%s"%text[length]
    return txet

How to change environment's font size?

As of mid 2017 To quickly get to the settings files press ctrl + shift + p and enter settings, there you will find the user settings and the workspace settings, be aware that the workspace settings will override the user settings, so it's better to use the latter directly to make it a global change (workspace settings will create a folder in your project root), from there you will have the option to add the option "editor.fontSize": 14 to your settings as a quick suggestion, but you can do it yourself and change the value to your preferred font size.

To sum it up:

  1. ctrl + shift + p

  2. select "user settings"

  3. add "editor.fontSize": 14

Random integer in VB.NET

Public Function RandomNumber(ByVal n As Integer) As Integer
    'initialize random number generator
    Dim r As New Random(System.DateTime.Now.Millisecond)
    Return r.Next(1, n)
End Function

configure Git to accept a particular self-signed server certificate for a particular https remote


  1. Get the self signed certificate
  2. Put it into some (e.g. ~/git-certs/cert.pem) file
  3. Set git to trust this certificate using http.sslCAInfo parameter

In more details:

Get self signed certificate of remote server

Assuming, the server URL is and you want to access it over port 443.

There are multiple options, how to get it.

Get certificate using openssl

$ openssl s_client -connect

Catch the output into a file cert.pem and delete all but part between (and including) -BEGIN CERTIFICATE- and -END CERTIFICATE-

Content of resulting file ~/git-certs/cert.pem may look like this:


Get certificate using your web browser

I use Redmine with Git repositories and I access the same URL for web UI and for git command line access. This way, I had to add exception for that domain into my web browser.

Using Firefox, I went to Options -> Advanced -> Certificates -> View Certificates -> Servers, found there the selfsigned host, selected it and using Export button I got exactly the same file, as created using openssl.

Note: I was a bit surprised, there is no name of the authority visibly mentioned. This is fine.

Having the trusted certificate in dedicated file

Previous steps shall result in having the certificate in some file. It does not matter, what file it is as long as it is visible to your git when accessing that domain. I used ~/git-certs/cert.pem

Note: If you need more trusted selfsigned certificates, put them into the same file:


This shall work (but I tested it only with single certificate).

Configure git to trust this certificate

$ git config --global http.sslCAInfo /home/javl/git-certs/cert.pem

You may also try to do that system wide, using --system instead of --global.

And test it: You shall now be able communicating with your server without resorting to:

$ git config --global http.sslVerify false #NO NEED TO USE THIS

If you already set your git to ignorance of ssl certificates, unset it:

$ git config --global --unset http.sslVerify

and you may also check, that you did it all correctly, without spelling errors:

$ git config --global --list

what should list all variables, you have set globally. (I mispelled http to htt).

How to add anchor tags dynamically to a div in Javascript?

<script type="text/javascript" language="javascript">
function createDiv()
  var divTag = document.createElement("div");            
  divTag.innerHTML = "Div tag created using Javascript DOM dynamically";        

Querying a linked sql server

You need to remove the quote marks from around the name of the linked server. It should be like this:

Select * from openquery(aa-db-dev01,'Select * from TestDB.dbo.users')

find all the name using mysql query which start with the letter 'a'

Try this simple select:

select * 
from artists 
where name like "a%"

C# Numeric Only TextBox Control

You might want to try int.TryParse(string, out int) in the KeyPress(object, KeyPressEventArgs) event to check for numeric values. For the other problem you could use regular expressions instead.

How to resolve git error: "Updates were rejected because the tip of your current branch is behind"

This worked for me:

git branch

Copy the current branch name to clipboard

git pull origin <paste-branch-name>
git push

How to show Error & Warning Message Box in .NET/ How to Customize MessageBox

Try details: use any option..

    MessageBox.Show("your message",
    "window title", 
    MessageBoxIcon.Warning // for Warning  
    //MessageBoxIcon.Error // for Error 
    //MessageBoxIcon.Information  // for Information
    //MessageBoxIcon.Question // for Question

How do you display a Toast from a background thread on Android?

I like to have a method in my activity called showToast which I can call from anywhere...

public void showToast(final String toast)
    runOnUiThread(() -> Toast.makeText(MyActivity.this, toast, Toast.LENGTH_SHORT).show());

I then most frequently call it from within MyActivity on any thread like this...


Error: Tablespace for table xxx exists. Please DISCARD the tablespace before IMPORT

In my case:

First remove tableName.ibd in your database directory from Mysql and second run:

DROP TABLE tableName;

.m2 , settings.xml in Ubuntu

.m2 directory on linux box usually would be $HOME/.m2

you could get the $HOME :

echo $HOME

or simply:

cd <enter>

to go to your home directory.

other information from maven site:

Right click to select a row in a Datagridview and show a menu to delete it

private void dataGridView1_CellContextMenuStripNeeded(object sender, 
DataGridViewCellContextMenuStripNeededEventArgs e)
    if (e.RowIndex != -1)
        this.dataGridView1.Rows[e.RowIndex].Selected = true;
        e.ContextMenuStrip = contextMenuStrip1;

/usr/bin/ld: cannot find

Add -L/opt/lib to your compiler parameters, this makes the compiler and linker search that path for in that folder.

Differences between "java -cp" and "java -jar"?

Like already said, the -cp is just for telling the jvm in the command line which class to use for the main thread and where it can find the libraries (define classpath). In -jar it expects the class-path and main-class to be defined in the jar file manifest. So other is for defining things in command line while other finding them inside the jar manifest. There is no difference in performance. You can't use them at the same time, -jar will override the -cp.

Though even if you use -cp, it will still check the manifest file. So you can define some of the class-paths in the manifest and some in the command line. This is particularly useful when you have a dependency on some 3rd party jar, which you might not provide with your build or don't want to provide (expecting it to be found already in the system where it's to be installed for example). So you can use it to provide external jars. It's location may vary between systems or it may even have a different version on different system (but having the same interfaces). This way you can build the app with other version and add the actual 3rd party dependency to class-path on the command line when running it on different systems.

C++ inheritance - inaccessible base?

You have to do this:

class Bar : public Foo
    // ...

The default inheritance type of a class in C++ is private, so any public and protected members from the base class are limited to private. struct inheritance on the other hand is public by default.

How to create JSON string in C#

Simlpe use of Newtonsoft.Json and Newtonsoft.Json.Linq libraries.

        //Create my object
        var my_jsondata = new
            Host = @"",
            UserName = "my_username",
            Password = "my_password",
            SourceDir = "/export/zip/mypath/",
            FileName = ""

        //Tranform it to Json object
        string json_data = JsonConvert.SerializeObject(my_jsondata);

        //Print the Json object

        //Parse the json object
        JObject json_object = JObject.Parse(json_data);

        //Print the parsed Json object

How do I delete a local repository in git?

To piggyback on rkj's answer, to avoid endless prompts (and force the command recursively), enter the following into the command line, within the project folder:

$ rm -rf .git

Or to delete .gitignore and .gitmodules if any (via @aragaer):

$ rm -rf .git*

Then from the same ex-repository folder, to see if hidden folder .git is still there:

$ ls -lah

If it's not, then congratulations, you've deleted your local git repo, but not a remote one if you had it. You can delete GitHub repo on their site (

To view hidden folders in Finder (Mac OS X) execute these two commands in your terminal window:

defaults write AppleShowAllFiles TRUE
killall Finder


What's the best way to add a full screen background image in React Native

Based on Braden Rockwell Napier's answer, I made this BackgroundImage component


import React, { Component } from 'react'
import { Image } from 'react-native'

class BackgroundImage extends Component {
  render() {
    const {source, children, style, ...props} = this.props
    return (
      <Image source={ source }
             style={ { flex: 1, width: null, height: null, } }
        { children }
BackgroundImage.propTypes = {
  source: React.PropTypes.object,
  children: React.PropTypes.object,
  style: React.PropTypes.object
export default BackgroundImage


 import BackgroundImage from './backgroundImage'
 <BackgroundImage source={ { uri: "" } }>

Error in Swift class: Property not initialized at super.init call

Add nil to the end of the declaration.

// Must be nil or swift complains
var someProtocol:SomeProtocol? = nil

// Init the view
override init(frame: CGRect)
    super.init(frame: frame)

This worked for my case, but may not work for yours

Forbidden You don't have permission to access / on this server

The problem lies in https.conf file!

# Virtual hosts
# Include conf/extra/httpd-vhosts.conf

The error occurs when hash(#) is removed or messed around with. These two lines should appear as shown above.

How can I check whether an array is null / empty?

In Java 8+ you achieve this with the help of streams allMatch method.

For primitive:

int[] k = new int[3]; -> element != 0)

For Object:

Objects[] k = new Objects[3];

scale Image in an UIButton to AspectFit?

Expanding on Dave's answer, you can set the contentMode of the button's imageView all in IB, without any code, using Runtime Attributes:

enter image description here

  • 1 means UIViewContentModeScaleAspectFit,
  • 2 would mean UIViewContentModeScaleAspectFill.

How to set different colors in HTML in one statement?

.rainbow {_x000D_
  background-image: -webkit-gradient( linear, left top, right top, color-stop(0, #f22), color-stop(0.15, #f2f), color-stop(0.3, #22f), color-stop(0.45, #2ff), color-stop(0.6, #2f2),color-stop(0.75, #2f2), color-stop(0.9, #ff2), color-stop(1, #f22) );_x000D_
  background-image: gradient( linear, left top, right top, color-stop(0, #f22), color-stop(0.15, #f2f), color-stop(0.3, #22f), color-stop(0.45, #2ff), color-stop(0.6, #2f2),color-stop(0.75, #2f2), color-stop(0.9, #ff2), color-stop(1, #f22) );_x000D_
  -webkit-background-clip: text;_x000D_
  background-clip: text;_x000D_
<h2><span class="rainbow">Rainbows are colorful and scalable and lovely</span></h2>