Programs & Examples On #Urllib

Python module providing a high-level interface for fetching data across the World Wide Web. Predecessor to urllib2. In Python 3, urllib2 and urllib have been reorganized and merged into urllib.

Handling urllib2's timeout? - Python

In Python 2.7.3:

import urllib2
import socket

class MyException(Exception):
    pass

try:
    urllib2.urlopen("http://example.com", timeout = 1)
except urllib2.URLError as e:
    print type(e)    #not catch
except socket.timeout as e:
    print type(e)    #catched
    raise MyException("There was an error: %r" % e)

python save image from url

import urllib.request
import os

img_url = "https://betanews.com/wp-content/uploads/2017/09/firefox-logo.jpg"
img_name = os.path.basename(img_url)
urllib.request.urlretrieve(img_url,img_name)

How to download a file over HTTP?

import urllib2
mp3file = urllib2.urlopen("http://www.example.com/songs/mp3.mp3")
with open('test.mp3','wb') as output:
  output.write(mp3file.read())

The wb in open('test.mp3','wb') opens a file (and erases any existing file) in binary mode so you can save data with it instead of just text.

UnicodeEncodeError: 'charmap' codec can't encode characters

In Python 3.7, and running Windows 10 this worked (I am not sure whether it will work on other platforms and/or other versions of Python)

Replacing this line:

with open('filename', 'w') as f:

With this:

with open('filename', 'w', encoding='utf-8') as f:

The reason why it is working is because the encoding is changed to UTF-8 when using the file, so characters in UTF-8 are able to be converted to text, instead of returning an error when it encounters a UTF-8 character that is not suppord by the current encoding.

no module named urllib.parse (How should I install it?)

You want urlparse using python2:

from urlparse import urlparse

SSL: CERTIFICATE_VERIFY_FAILED with Python3

In my case, I used the ssl module to "workaround" the certification like so:

import ssl

ssl._create_default_https_context = ssl._create_unverified_context

Then to read your link content, you can use:

urllib.request.urlopen(urllink)

How to urlencode a querystring in Python?

Context

  • Python (version 2.7.2 )

Problem

  • You want to generate a urlencoded query string.
  • You have a dictionary or object containing the name-value pairs.
  • You want to be able to control the output ordering of the name-value pairs.

Solution

  • urllib.urlencode
  • urllib.quote_plus

Pitfalls

Example

The following is a complete solution, including how to deal with some pitfalls.

### ********************
## init python (version 2.7.2 )
import urllib

### ********************
## first setup a dictionary of name-value pairs
dict_name_value_pairs = {
  "bravo"   : "True != False",
  "alpha"   : "http://www.example.com",
  "charlie" : "hello world",
  "delta"   : "1234567 !@#$%^&*",
  "echo"    : "[email protected]",
  }

### ********************
## setup an exact ordering for the name-value pairs
ary_ordered_names = []
ary_ordered_names.append('alpha')
ary_ordered_names.append('bravo')
ary_ordered_names.append('charlie')
ary_ordered_names.append('delta')
ary_ordered_names.append('echo')

### ********************
## show the output results
if('NO we DO NOT care about the ordering of name-value pairs'):
  queryString  = urllib.urlencode(dict_name_value_pairs)
  print queryString 
  """
  echo=user%40example.com&bravo=True+%21%3D+False&delta=1234567+%21%40%23%24%25%5E%26%2A&charlie=hello+world&alpha=http%3A%2F%2Fwww.example.com
  """

if('YES we DO care about the ordering of name-value pairs'):
  queryString  = "&".join( [ item+'='+urllib.quote_plus(dict_name_value_pairs[item]) for item in ary_ordered_names ] )
  print queryString
  """
  alpha=http%3A%2F%2Fwww.example.com&bravo=True+%21%3D+False&charlie=hello+world&delta=1234567+%21%40%23%24%25%5E%26%2A&echo=user%40example.com
  """ 

I/O error(socket error): [Errno 111] Connection refused

Its seems that server is not running properly so ensure that with terminal by

telnet ip port

example

telnet localhost 8069

It will return connected to localhost so it indicates that there is no problem with the connection Else it will return Connection refused it indicates that there is problem with the connection

AttributeError: 'module' object has no attribute 'urlopen'

Solution for python3:

from urllib.request import urlopen

url = 'http://www.python.org'
file = urlopen(url)
html = file.read()
print(html)

Python 2.7.10 error "from urllib.request import urlopen" no module named request

Change

from urllib.request import urlopen

to

from urllib import urlopen

I was able to solve this problem by changing like this. For Python2.7 in macOS10.14

Python: URLError: <urlopen error [Errno 10060]

Answer (Basic is advance!):

Error: 10060 Adding a timeout parameter to request solved the issue for me.

Example 1

import urllib
import urllib2
g = "http://www.google.com/"
read = urllib2.urlopen(g, timeout=20)

Example 2

A similar error also occurred while I was making a GET request. Again, passing a timeout parameter solved the 10060 Error.

response = requests.get(param_url, timeout=20)

can we use xpath with BeautifulSoup?

I can confirm that there is no XPath support within Beautiful Soup.

installing urllib in Python3.6

urllib is a standard python library (built-in) so you don't have to install it. just import it if you need to use request by:

import urllib.request

if it's not work maybe you compiled python in wrong way, so be kind and give us more details.

Python: Get HTTP headers from urllib2.urlopen call?

One-liner:

$ python -c "import urllib2; print urllib2.build_opener(urllib2.HTTPHandler(debuglevel=1)).open(urllib2.Request('http://google.com'))"

Python; urllib error: AttributeError: 'bytes' object has no attribute 'read'

I'm not familiar with python 3 yet, but it seems like urllib.request.urlopen().read() returns a byte object rather than string.

You might try to feed it into a StringIO object, or even do a str(response).

How to send POST request?

If you don't want to use a module you have to install like requests, and your use case is very basic, then you can use urllib2

urllib2.urlopen(url, body)

See the documentation for urllib2 here: https://docs.python.org/2/library/urllib2.html.

urllib2.HTTPError: HTTP Error 403: Forbidden

import urllib.request

bank_pdf_list = ["https://www.hdfcbank.com/content/bbp/repositories/723fb80a-2dde-42a3-9793-7ae1be57c87f/?path=/Personal/Home/content/rates.pdf",
"https://www.yesbank.in/pdf/forexcardratesenglish_pdf",
"https://www.sbi.co.in/documents/16012/1400784/FOREX_CARD_RATES.pdf"]


def get_pdf(url):
    user_agent = 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.7) Gecko/2009021910 Firefox/3.0.7'
    
    #url = "https://www.yesbank.in/pdf/forexcardratesenglish_pdf"
    headers={'User-Agent':user_agent,} 
    
    request=urllib.request.Request(url,None,headers) #The assembled request
    response = urllib.request.urlopen(request)
    #print(response.text)
    data = response.read()
#    print(type(data))
    
    name = url.split("www.")[-1].split("//")[-1].split(".")[0]+"_FOREX_CARD_RATES.pdf"
    f = open(name, 'wb')
    f.write(data)
    f.close()
    

for bank_url in bank_pdf_list:
    try: 
        get_pdf(bank_url)
    except:
        pass

Making a POST call instead of GET using urllib2

This may have been answered before: Python URLLib / URLLib2 POST.

Your server is likely performing a 302 redirect from http://myserver/post_service to http://myserver/post_service/. When the 302 redirect is performed, the request changes from POST to GET (see Issue 1401). Try changing url to http://myserver/post_service/.

Python: Importing urllib.quote

urllib went through some changes in Python3 and can now be imported from the parse submodule

>>> from urllib.parse import quote  
>>> quote('"')                      
'%22'                               

urllib and "SSL: CERTIFICATE_VERIFY_FAILED" Error

In python 2.7 adding Trusted root CA details at the end in file C:\Python27\lib\site-packages\certifi\cacert.pem helped

after that i did run (using admin rights) pip install --trusted-host pypi.python.org --trusted-host pypi.org --trusted-host files.pythonhosted.org packageName

'module' has no attribute 'urlencode'

You use the Python 2 docs but write your program in Python 3.

How do I set headers using python's urllib?

adding HTTP headers using urllib2:

from the docs:

import urllib2
req = urllib2.Request('http://www.example.com/')
req.add_header('Referer', 'http://www.python.org/')
resp = urllib2.urlopen(req)
content = resp.read()

In Python, how do I use urllib to see if a website is 404 or 200?

You can use urllib2 as well:

import urllib2

req = urllib2.Request('http://www.python.org/fish.html')
try:
    resp = urllib2.urlopen(req)
except urllib2.HTTPError as e:
    if e.code == 404:
        # do something...
    else:
        # ...
except urllib2.URLError as e:
    # Not an HTTP-specific error (e.g. connection refused)
    # ...
else:
    # 200
    body = resp.read()

Note that HTTPError is a subclass of URLError which stores the HTTP status code.

Downloading a picture via urllib and python

A simpler solution may be(python 3):

import urllib.request
import os
os.chdir("D:\\comic") #your path
i=1;
s="00000000"
while i<1000:
    try:
        urllib.request.urlretrieve("http://www.gunnerkrigg.com//comics/"+ s[:8-len(str(i))]+ str(i)+".jpg",str(i)+".jpg")
    except:
        print("not possible" + str(i))
    i+=1;

How to percent-encode URL parameters in Python?

In Python 3, urllib.quote has been moved to urllib.parse.quote and it does handle unicode by default.

>>> from urllib.parse import quote
>>> quote('/test')
'/test'
>>> quote('/test', safe='')
'%2Ftest'
>>> quote('/El Niño/')
'/El%20Ni%C3%B1o/'

Python URLLib / URLLib2 POST

u = urllib2.urlopen('http://myserver/inout-tracker', data)
h.request('POST', '/inout-tracker/index.php', data, headers)

Using the path /inout-tracker without a trailing / doesn't fetch index.php. Instead the server will issue a 302 redirect to the version with the trailing /.

Doing a 302 will typically cause clients to convert a POST to a GET request.

catch specific HTTP error in python

Tims answer seems to me as misleading. Especially when urllib2 does not return expected code. For example this Error will be fatal (believe or not - it is not uncommon one when downloading urls):

AttributeError: 'URLError' object has no attribute 'code'

Fast, but maybe not the best solution would be code using nested try/except block:

import urllib2
try:
    urllib2.urlopen("some url")
except urllib2.HTTPError, err:
    try:
        if err.code == 404:
            # Handle the error
        else:
            raise
    except:
        ...

More information to the topic of nested try/except blocks Are nested try/except blocks in python a good programming practice?

AttributeError: 'module' object has no attribute 'urlretrieve'

Suppose you have following lines of code

MyUrl = "www.google.com" #Your url goes here
urllib.urlretrieve(MyUrl)

If you are receiving following error message

AttributeError: module 'urllib' has no attribute 'urlretrieve'

Then you should try following code to fix the issue:

import urllib.request
MyUrl = "www.google.com" #Your url goes here
urllib.request.urlretrieve(MyUrl)

replace special characters in a string python

You can replace the special characters with the desired characters as follows,

import string
specialCharacterText = "H#y #@w @re &*)?"
inCharSet = "!@#$%^&*()[]{};:,./<>?\|`~-=_+\""
outCharSet = "                               " #corresponding characters in inCharSet to be replaced
splCharReplaceList = string.maketrans(inCharSet, outCharSet)
splCharFreeString = specialCharacterText.translate(splCharReplaceList)

What are the differences between the urllib, urllib2, urllib3 and requests module?

Just to add to the existing answers, I don't see anyone mentioning that python requests is not a native library. If you are ok with adding dependencies, then requests is fine. However, if you are trying to avoid adding dependencies, urllib is a native python library that is already available to you.

angularjs: ng-src equivalent for background-image:url(...)

@jaime your answer is fine. But if your page has the $http.get then you have use ng-if

app.directive('backImg', function(){
    return function($scope, $element, $attrs){
        var url = $attrs.backImg;
        $element.css({
            'background-image': 'url(' + url + ')',
            'background-size': 'cover'
        });
    }
});

in the factory

app.factory('dataFactory', function($http){
    var factory = {};
    factory.getAboutData = function(){
        return $http.get("api/about-data.json");
    };
    return factory;
});

in the controller area

app.controller('aboutCtrl', function($scope, $http, dataFactory){
    $scope.aboutData = [];
    dataFactory.getAboutData().then(function(response){
        // get full home data
        $scope.aboutData = response.data;
        // banner data
        $scope.banner = {
            "image": $scope.aboutData.bannerImage,
            "text": $scope.aboutData.bannerText
        };
    });
});

and the view if you use the ng-if like below then you will get the image by interpolation otherwise, you can't get the image because directive get the value before HTTP request.

<div class="stat-banner"  ng-if="banner.image" background-image-directive="{{banner.image}}">

IsNull function in DB2 SQL?

I'm not familiar with DB2, but have you tried COALESCE?

ie:


SELECT Product.ID, COALESCE(product.Name, "Internal") AS ProductName
FROM Product

Where does Java's String constant pool live, the heap or the stack?

The answer is technically neither. According to the Java Virtual Machine Specification, the area for storing string literals is in the runtime constant pool. The runtime constant pool memory area is allocated on a per-class or per-interface basis, so it's not tied to any object instances at all. The runtime constant pool is a subset of the method area which "stores per-class structures such as the runtime constant pool, field and method data, and the code for methods and constructors, including the special methods used in class and instance initialization and interface type initialization". The VM spec says that although the method area is logically part of the heap, it doesn't dictate that memory allocated in the method area be subject to garbage collection or other behaviors that would be associated with normal data structures allocated to the heap.

Class Not Found Exception when running JUnit test

After having tried everything here with no improvement, I solved my issue by just restarting Eclipse

What's the difference between struct and class in .NET?

In .NET, there are two categories of types, reference types and value types.

Structs are value types and classes are reference types.

The general difference is that a reference type lives on the heap, and a value type lives inline, that is, wherever it is your variable or field is defined.

A variable containing a value type contains the entire value type value. For a struct, that means that the variable contains the entire struct, with all its fields.

A variable containing a reference type contains a pointer, or a reference to somewhere else in memory where the actual value resides.

This has one benefit, to begin with:

  • value types always contains a value
  • reference types can contain a null-reference, meaning that they don't refer to anything at all at the moment

Internally, reference types are implemented as pointers, and knowing that, and knowing how variable assignment works, there are other behavioral patterns:

  • copying the contents of a value type variable into another variable, copies the entire contents into the new variable, making the two distinct. In other words, after the copy, changes to one won't affect the other
  • copying the contents of a reference type variable into another variable, copies the reference, which means you now have two references to the same somewhere else storage of the actual data. In other words, after the copy, changing the data in one reference will appear to affect the other as well, but only because you're really just looking at the same data both places

When you declare variables or fields, here's how the two types differ:

  • variable: value type lives on the stack, reference type lives on the stack as a pointer to somewhere in heap memory where the actual memory lives (though note Eric Lipperts article series: The Stack Is An Implementation Detail.)
  • class/struct-field: value type lives completely inside the type, reference type lives inside the type as a pointer to somewhere in heap memory where the actual memory lives.

How do I determine the size of my array in C?

Note: This one can give you undefined behaviour as pointed by M.M in the comment.

int a[10];
int size = (*(&a+1)-a) ;

For more details see here and also here.

Recursively list files in Java

    private void fillFilesRecursively(File file, List<File> resultFiles) {
        if (file.isFile()) {
            resultFiles.add(file);
        } else {
            for (File child : file.listFiles()) {
                fillFilesRecursively(child, resultFiles);
            }
        }
    }

Flexbox: center horizontally and vertically

Hope this will help.

.flex-container {
  padding: 0;
  margin: 0;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: center;
}
row {
  width: 100%;
}
.flex-item {
  background: tomato;
  padding: 5px;
  width: 200px;
  height: 150px;
  margin: 10px;
  line-height: 150px;
  color: white;
  font-weight: bold;
  font-size: 3em;
  text-align: center;
}

Difference between \w and \b regular expression meta characters

\w is not a word boundary, it matches any word character, including underscores: [a-zA-Z0-9_]. \b is a word boundary, that is, it matches the position between a word and a non-alphanumeric character: \W or [^\w].

These implementations may vary from language to language though.

How to get html table td cell value by JavaScript?

I gave the table an id so I could find it. On onload (when the page is loaded by the browser), I set onclick event handlers to all rows of the table. Those handlers alert the content of the first cell.

<!DOCTYPE html>
<html>
    <head>
        <script>
            var p = {
                onload: function() {
                    var rows = document.getElementById("mytable").rows;
                    for(var i = 0, ceiling = rows.length; i < ceiling; i++) {
                        rows[i].onclick = function() {
                            alert(this.cells[0].innerHTML);
                        }
                    }
                }
            };
        </script>
    </head>
    <body onload="p.onload()">
        <table id="mytable">
            <tr>
                <td>0</td>
                <td>row 1 cell 2</td>
            </tr>
            <tr>
                <td>1</td>
                <td>row 2 cell 2</td>
            </tr>
        </table>    
    </body>
</html> 

Why SpringMVC Request method 'GET' not supported?

I also had the same issue. I changed it to the following and it worked.

Java :

@RequestMapping(value = "/test", method = RequestMethod.GET)

HTML code:

  <form action="<%=request.getContextPath() %>/test" method="GET">
    <input type="submit" value="submit"> 
    </form>

By default if you do not specify http method in a form it uses GET. To use POST method you need specifically state it.

Hope this helps.

Bootstrap 4 datapicker.js not included

Maybe you want to try this: https://bootstrap-datepicker.readthedocs.org/en/latest/index.html

It's a flexible datepicker widget in the Bootstrap style.

Regex for empty string or white space

The \ (backslash) in the .match call is not properly escaped. It would be easier to use a regex literal though. Either will work:

var regex = "^\\s+$";
var regex = /^\s+$/;

Also note that + will require at least one space. You may want to use *.

How should I escape commas and speech marks in CSV files so they work in Excel?

Single quotes work fine too, even without escaping the double quotes, at least in Excel 2016:

'text with spaces, and a comma','more text with spaces','spaces and "quoted text" and more spaces','nospaces','NOSPACES1234'

Excel will put that in 5 columns (if you choose the single quote as "Text qualifier" in the "Text to columns" wizard)

Maximum and minimum values in a textbox

Here's a simple function that does what you need:

<script type="text/javascript">
function minmax(value, min, max) 
{
    if(parseInt(value) < min || isNaN(parseInt(value))) 
        return min; 
    else if(parseInt(value) > max) 
        return max; 
    else return value;
}
</script>
<input type="text" name="textWeight" id="txtWeight" maxlength="5" onkeyup="this.value = minmax(this.value, 0, 100)"/>

If the input is not numeric it replaces it with a zero

Google Maps API warning: NoApiKeys

Google maps requires an API key for new projects since june 2016. For more information take a look at the Google Developers Blog. Also more information in german you'll find at this blog post from the clickstorm Blog.

Is there any way to return HTML in a PHP function? (without building the return value as a string)

Create a template file and use a template engine to read/update the file. It will increase your code's maintainability in the future as well as separate display from logic.

An example using Smarty:

Template File

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head><title>{$title}</title></head>
<body>{$string}</body>
</html>

Code

function TestBlockHTML(){
  $smarty = new Smarty();
  $smarty->assign('title', 'My Title');
  $smarty->assign('string', $replStr);
  return $smarty->render('template.tpl');
}

Validate that end date is greater than start date with jQuery

var startDate = new Date($('#startDate').val());
var endDate = new Date($('#endDate').val());

if (startDate < endDate){
// Do something
}

That should do it I think

MySQL: What's the difference between float and double?

Float has 32 bit (4 bytes) with 8 places accuracy. Double has 64 bit (8 bytes) with 16 places accuracy.

If you need better accuracy, use Double instead of Float.

Plugin org.apache.maven.plugins:maven-compiler-plugin or one of its dependencies could not be resolved

I accidentally turned on offline mode.

To disable it: in the Maven tool window, click The Toggle Offline Mode button.

enter image description here

How to generate the "create table" sql statement for an existing table in postgreSQL

pg_dump -h XXXXXXXXXXX.us-west-1.rds.amazonaws.com -U anyuser -t tablename -s

Better way to Format Currency Input editText?

This is like Saeid Mohammadi answer but I changed to accept negative numbers.

  package com.example.liberdade.util
    
    import android.text.Editable
    import android.text.TextWatcher
    import android.widget.EditText
    import java.lang.ref.WeakReference
    import java.math.BigDecimal
    import java.text.NumberFormat
    import java.util.*
    
    
    class MoneyTextWatcher : TextWatcher {
    
    
    
        private val editTextWeakReference: WeakReference<EditText?>?
        private val locale: Locale = Locale("pt", "BR")
        //private final Locale locale;
    
        constructor(editText: EditText?, locale: Locale?) {
            editTextWeakReference = WeakReference<EditText?>(editText)
            //this.locale = if (locale != null) locale else Locale.getDefault()
        }
    
        constructor(editText: EditText?) {
            editTextWeakReference = WeakReference<EditText?>(editText)
            //locale = Locale.getDefault()
        }
    
        override fun beforeTextChanged(
            s: CharSequence?,
            start: Int,
            count: Int,
            after: Int
        ) {
        }
    
        override fun onTextChanged(
            s: CharSequence?,
            start: Int,
            before: Int,
            count: Int
        ) {
        }
    
        override fun afterTextChanged(editable: Editable?) {
            val editText: EditText = editTextWeakReference?.get() ?: return
            editText.removeTextChangedListener(this)
    
            var isNegative = false
            var editableString = editable.toString()
            if (editable != null) {
                if (editableString.contains('-')) {
                    isNegative = true
                    if (editable != null) {
                        editableString = editableString.replace("-","")
                    }
                }
            }
    
            val parsed: BigDecimal? = parseToBigDecimal(editableString, locale)
            //val parsed: BigDecimal? = parseToBigDecimal(editable.toString(), locale)
            var formatted: String = NumberFormat.getCurrencyInstance(locale).format(parsed)
    
            if (isNegative && !(formatted.equals("R\$ 0,00") || formatted.equals("-R\$ 0,00"))) formatted = "-${formatted}"
            editText.setText(formatted)
            editText.setSelection(formatted.length)
            editText.addTextChangedListener(this)
        }
    
        private fun parseToBigDecimal(value: String?, locale: Locale?): BigDecimal? {
            val replaceable = java.lang.String.format(
                "[%s,.\\s]",
                NumberFormat.getCurrencyInstance(locale).currency.symbol
            )
            val cleanString = value!!.replace(replaceable.toRegex(), "")
            return BigDecimal(cleanString).setScale(
                2, BigDecimal.ROUND_FLOOR
            ).divide(
                BigDecimal(100), BigDecimal.ROUND_FLOOR
            )
        }
    }
    
    //como invocar
    //binding.editTextValorCaixa.addTextChangedListener(MoneyTextWatcher(binding.editTextValorCaixa, Locale("pt", "BR")))

Visual Studio Code: Auto-refresh file changes

VSCode will never refresh the file if you have changes in that file that are not saved to disk. However, if the file is open and does not have changes, it will replace with the changes on disk, that is true.

There is currently no way to disable this behaviour.

SQL Server date format yyyymmdd

SELECT TO_CHAR(created_at, 'YYYY-MM-DD') FROM table; //converts any date format to YYYY-MM-DD

How can I find whitespace in a String?

import java.util.Scanner;
public class camelCase {

public static void main(String[] args)
{
    Scanner user_input=new Scanner(System.in);
    String Line1;
    Line1 = user_input.nextLine();
    int j=1;
    //Now Read each word from the Line and convert it to Camel Case

    String result = "", result1 = "";
    for (int i = 0; i < Line1.length(); i++) {
        String next = Line1.substring(i, i + 1);
        System.out.println(next + "  i Value:" + i + "  j Value:" + j);
        if (i == 0 | j == 1 )
        {
            result += next.toUpperCase();
        } else {
            result += next.toLowerCase();
        }

        if (Character.isWhitespace(Line1.charAt(i)) == true)
        {
            j=1;
        }
        else
        {
            j=0;
        }
    }
    System.out.println(result);

APR based Apache Tomcat Native library was not found on the java.library.path?

For Ubntu Users

 1. Install compilers
    #sudo apt-get install make
    #sudo apt-get install gcc

    2. Install openssl and development libraries
    #sudo apt-get install openssl
    #sudo apt-get install libssl-dev
    3. Install the APR package (Downloaded from http://apr.apache.org/)

    #tar -xzf apr-1.4.6.tar.gz
    #cd apr-1.4.6/
    #sudo ./configure
    #sudo make
    #sudo make install

    You should see the compiled file as
    /usr/local/apr/lib/libapr-1.a

    4. Download, compile and install Tomcat Native sourse package
    tomcat-native-1.1.27-src.tar.gz

    Extract the archive into some folder

    #tar -xzf tomcat-native-1.1.27-src.tar.gz
    #cd tomcat-native-1.1.27-src/jni/native
    #JAVA_HOME=/usr/lib/jvm/jdk1.7.0_21/
    #sudo ./configure --with-apr=/usr/local/apr --with-java-home=$JAVA_HOME
    #sudo make
    #sudo make install

    Now I have compiled Tomcat Native library in /usr/local/apr/libtcnative-1.so.0.1.27 and symbolic link file /usr/local/apr/@libtcnative-1.so pointed to the library

    5. Create or edit the $CATALINA_HOME/bin/setenv.sh file with following lines :
    export LD_LIBRARY_PATH='$LD_LIBRARY_PATH:/usr/local/apr/lib'

    6. Restart tomcat and see the desired result:

Bold black cursor in Eclipse deletes code, and I don't know how to get rid of it

You might have pressed 0 (also used for insert, shortcut INS) key, which is on the right side of your right scroll button. To solve the problem, just press it again or double click on 'overwrite'.

Sort a List of objects by multiple fields

If you know in advance which fields to use to make the comparison, then other people gave right answers.
What you may be interested in is to sort your collection in case you don't know at compile-time which criteria to apply. Imagine you have a program dealing with cities:



    protected Set<City> cities;
    (...)
    Field temperatureField = City.class.getDeclaredField("temperature");
    Field numberOfInhabitantsField = City.class.getDeclaredField("numberOfInhabitants");
    Field rainfallField = City.class.getDeclaredField("rainfall");
    program.showCitiesSortBy(temperatureField, numberOfInhabitantsField, rainfallField);
    (...)
    public void showCitiesSortBy(Field... fields) {
        List<City> sortedCities = new ArrayList<City>(cities);
        Collections.sort(sortedCities, new City.CityMultiComparator(fields));
        for (City city : sortedCities) {
            System.out.println(city.toString());
        }
    }

where you can replace hard-coded field names by field names deduced from a user request in your program.

In this example, City.CityMultiComparator<City> is a static nested class of class City implementing Comparator:



    public static class CityMultiComparator implements Comparator<City> {
        protected List<Field> fields;

        public CityMultiComparator(Field... orderedFields) {
            fields = new ArrayList<Field>();
            for (Field field : orderedFields) {
                fields.add(field);
            }
        }

        @Override
        public int compare(City cityA, City cityB) {
            Integer score = 0;
            Boolean continueComparison = true;
            Iterator itFields = fields.iterator();

            while (itFields.hasNext() && continueComparison) {
                Field field = itFields.next();
                Integer currentScore = 0;
                if (field.getName().equalsIgnoreCase("temperature")) {
                    currentScore = cityA.getTemperature().compareTo(cityB.getTemperature());
                } else if (field.getName().equalsIgnoreCase("numberOfInhabitants")) {
                    currentScore = cityA.getNumberOfInhabitants().compareTo(cityB.getNumberOfInhabitants());
                } else if (field.getName().equalsIgnoreCase("rainfall")) {
                    currentScore = cityA.getRainfall().compareTo(cityB.getRainfall());
                }
                if (currentScore != 0) {
                    continueComparison = false;
                }
                score = currentScore;
            }

            return score;
        }
    }


You may want to add an extra layer of precision, to specify, for each field, whether sorting should be ascendant or descendant. I guess a solution is to replace Field objects by objects of a class you could call SortedField, containing a Field object, plus another field meaning ascendant or descendant.

Entity Framework: One Database, Multiple DbContexts. Is this a bad idea?

Reminder: If you do combine multiple contexts make sure you cut n paste all the functionality in your various RealContexts.OnModelCreating() into your single CombinedContext.OnModelCreating().

I just wasted time hunting down why my cascade delete relationships weren't being preserved only to discover that I hadn't ported the modelBuilder.Entity<T>()....WillCascadeOnDelete(); code from my real context into my combined context.

What is middleware exactly?

it is a software layer between the operating system and applications on each side of a distributed computing system in a network. In fact it connects heterogeneous network and software systems.

SQL Query to fetch data from the last 30 days?

Try this : Using this you can select data from last 30 days

SELECT
    *
FROM
    product
WHERE
    purchase_date > DATE_SUB(CURDATE(), INTERVAL 1 MONTH)

Pass user defined environment variable to tomcat

Environment Entries specified by <Environment> markup are JNDI, accessible using InitialContext.lookup under java:/comp/env. You can specify environment properties to the JNDI by using the environment parameter to the InitialContext constructor and application resource files.

System.getEnv() is about system environment variables of the tomcat process itself.

To set an environment variable using bash command : export TOMCAT_OPTS=-Dmy.bar=foo and start the Tomcat : ./startup.sh To retrieve the value of System property bar use System.getProperty(). System.getEnv() can be used to retrieve the environment variable i.e. TOMCAT_OPTS.

Does IE9 support console.log, and is it a real function?

console.log is only defined when the console is open. If you want to check for it in your code make sure you check for for it within the window property

if (window.console)
    console.log(msg)

this throws an exception in IE9 and will not work correctly. Do not do this

if (console) 
    console.log(msg)

Set default time in bootstrap-datetimepicker

It works for me:

 <script type="text/javascript">
        $(function () {
            var dateNow = new Date();
            $('#calendario').datetimepicker({
                locale: 'es',
                format: 'DD/MM/YYYY',
                defaultDate:moment(dateNow).hours(0).minutes(0).seconds(0).milliseconds(0)                    
            });
        });            
    </script>

Link to "pin it" on pinterest without generating a button

For such cases, I found very useful the Share Link Generator, it helps creating Facebook, Google+, Twitter, Pinterest, LinkedIn share buttons.

Ternary operators in JavaScript without an "else"

In your case i see the ternary operator as redundant. You could assign the variable directly to the expression, using ||, && operators.

!defaults.slideshowWidth ? defaults.slideshowWidth = obj.find('img').width()+'px' : null ;

will become :

defaults.slideshowWidth = defaults.slideshowWidth || obj.find('img').width()+'px';

It's more clear, it's more "javascript" style.

Can an angular directive pass arguments to functions in expressions specified in the directive's attributes?

Nothing wrong with the other answers, but I use the following technique when passing functions in a directive attribute.

Leave off the parenthesis when including the directive in your html:

<my-directive callback="someFunction" />

Then "unwrap" the function in your directive's link or controller. here is an example:

app.directive("myDirective", function() {

    return {
        restrict: "E",
        scope: {
            callback: "&"                              
        },
        template: "<div ng-click='callback(data)'></div>", // call function this way...
        link: function(scope, element, attrs) {
            // unwrap the function
            scope.callback = scope.callback(); 

            scope.data = "data from somewhere";

            element.bind("click",function() {
                scope.$apply(function() {
                    callback(data);                        // ...or this way
                });
            });
        }
    }
}]);    

The "unwrapping" step allows the function to be called using a more natural syntax. It also ensures that the directive works properly even when nested within other directives that may pass the function. If you did not do the unwrapping, then if you have a scenario like this:

<outer-directive callback="someFunction" >
    <middle-directive callback="callback" >
        <inner-directive callback="callback" />
    </middle-directive>
</outer-directive>

Then you would end up with something like this in your inner-directive:

callback()()()(data); 

Which would fail in other nesting scenarios.

I adapted this technique from an excellent article by Dan Wahlin at http://weblogs.asp.net/dwahlin/creating-custom-angularjs-directives-part-3-isolate-scope-and-function-parameters

I added the unwrapping step to make calling the function more natural and to solve for the nesting issue which I had encountered in a project.

How to get a user's time zone?

NSTimeZone *timeZone = [NSTimeZone localTimeZone];
NSString *tzName = [timeZone name];

The name will be something like "Australia/Sydney", or "Europe/Lisbon".

Since it sounds like you might only care about the continent, that might be all you need.

Common elements comparison between 2 lists

you can use a simple list comprehension:

x=[1,2,3,4]
y=[3,4,5]
common = [i for i in x if i in y]
common: [3,4]

Changing the browser zoom level

as the the accepted answer mentioned, you can enlarge the fontSize css attribute of the element in DOM one by one, the following code for your reference.

 <script>
    var factor = 1.2;
    var all = document.getElementsByTagName("*");
    for (var i=0, max=all.length; i < max; i++) {
        var style = window.getComputedStyle(all[i]);
        var fontSize = style.getPropertyValue('font-size');

        if(fontSize){
            all[i].style.fontSize=(parseFloat(fontSize)*factor)+"px";
        }
        if(all[i].nodeName === "IMG"){
            var width=style.getPropertyValue('width');
            var height=style.getPropertyValue('height');
            all[i].style.height = (parseFloat(height)*factor)+"px";
            all[i].style.width = (parseFloat(width)*factor)+"px";
        }
    }
</script>

Finding out the name of the original repository you cloned from in Git

git remote show origin -n | ruby -ne 'puts /^\s*Fetch.*(:|\/){1}([^\/]+\/[^\/]+).git/.match($_)[2] rescue nil'

It was tested with three different URL styles:

echo "Fetch URL: http://user@pass:gitservice.org:20080/owner/repo.git" | ruby -ne 'puts /^\s*Fetch.*(:|\/){1}([^\/]+\/[^\/]+).git/.match($_)[2] rescue nil'
echo "Fetch URL: Fetch URL: [email protected]:home1-oss/oss-build.git" | ruby -ne 'puts /^\s*Fetch.*(:|\/){1}([^\/]+\/[^\/]+).git/.match($_)[2] rescue nil'
echo "Fetch URL: https://github.com/owner/repo.git" | ruby -ne 'puts /^\s*Fetch.*(:|\/){1}([^\/]+\/[^\/]+).git/.match($_)[2] rescue nil'

How does Tomcat find the HOME PAGE of my Web App?

I already had index.html in the WebContent folder but it was not showing up , finally i added the following piece of code in my projects web.xml and it started showing up

  <servlet-mapping>
    <servlet-name>default</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping> 

Truncate a string straight JavaScript

_x000D_
_x000D_
var pa = document.getElementsByTagName('p')[0].innerHTML;_x000D_
var rpa = document.getElementsByTagName('p')[0];_x000D_
// console.log(pa.slice(0, 30));_x000D_
var newPa = pa.slice(0, 29).concat('...');_x000D_
rpa.textContent = newPa;_x000D_
console.log(newPa)
_x000D_
<p>_x000D_
some text here some text here some text here some text here some text here some text here some text here some text here some text here some text here some text here some text here some text here some text here some text here_x000D_
</p>
_x000D_
_x000D_
_x000D_

How to measure time taken between lines of code in python?

I always prefer to check time in hours, minutes and seconds (%H:%M:%S) format:

from datetime import datetime
start = datetime.now()
# your code
end = datetime.now()
time_taken = end - start
print('Time: ',time_taken) 

output:

Time:  0:00:00.000019

Summarizing count and conditional aggregate functions on the same factor

Assuming that your original dataset is similar to the one you created (i.e. with NA as character. You could specify na.strings while reading the data using read.table. But, I guess NAs would be detected automatically.

The price column is factor which needs to be converted to numeric class. When you use as.numeric, all the non-numeric elements (i.e. "NA", FALSE) gets coerced to NA) with a warning.

library(dplyr)
df %>%
     mutate(price=as.numeric(as.character(price))) %>%  
     group_by(company, year, product) %>%
     summarise(total.count=n(), 
               count=sum(is.na(price)), 
               avg.price=mean(price,na.rm=TRUE),
               max.price=max(price, na.rm=TRUE))

data

I am using the same dataset (except the ... row) that was showed.

df = tbl_df(data.frame(company=c("Acme", "Meca", "Emca", "Acme", "Meca","Emca"),
 year=c("2011", "2010", "2009", "2011", "2010", "2013"), product=c("Wrench", "Hammer",
 "Sonic Screwdriver", "Fairy Dust", "Kindness", "Helping Hand"), price=c("5.67",
 "7.12", "12.99", "10.99", "NA",FALSE)))

How do I force Maven to use my local repository rather than going out to remote repos to retrieve artifacts?

Even when considering all answers above you might still run into issues that will terminate your maven offline build with an error. Especially, you may experience a warning as follwos:

[WARNING] The POM for org.apache.maven.plugins:maven-resources-plugin:jar:2.6 is missing, no dependency information available

The warning will be immediately followed by further errors and maven will terminate.

For us the safest way to build offline with a maven offline cache created following the hints above is to use following maven offline parameters:

mvn -o -llr -Dmaven.repo.local=<path_to_your_offline_cache> ...

Especially, option -llr prevents you from having to tune your local cache as proposed in answer #4.

Also take care that that the localRepository parameter in settings.xml is set as follows:

<localRepository>${user.home}/.m2/repository</localRepository>

Ruby on Rails. How do I use the Active Record .build method in a :belongs to relationship?

Where it is documented:

From the API documentation under the has_many association in "Module ActiveRecord::Associations::ClassMethods"

collection.build(attributes = {}, …) Returns one or more new objects of the collection type that have been instantiated with attributes and linked to this object through a foreign key, but have not yet been saved. Note: This only works if an associated object already exists, not if it‘s nil!

The answer to building in the opposite direction is a slightly altered syntax. In your example with the dogs,

Class Dog
   has_many :tags
   belongs_to :person
end

Class Person
  has_many :dogs
end

d = Dog.new
d.build_person(:attributes => "go", :here => "like normal")

or even

t = Tag.new
t.build_dog(:name => "Rover", :breed => "Maltese")

You can also use create_dog to have it saved instantly (much like the corresponding "create" method you can call on the collection)

How is rails smart enough? It's magic (or more accurately, I just don't know, would love to find out!)

"Parse Error : There is a problem parsing the package" while installing Android application

You might also want to check the logs on the device to see if it's something simple like a permissions problem. You can check the logs using adb from a host/debug computer:

adb logcat

Or if you have access to the console (or when using Android-x86 get console by typing Alt+F1) then you can check the logs by using the logcat command:

logcat

File upload progress bar with jQuery

I have used the following in my project. you can try too.

ajax = new XMLHttpRequest();
ajax.onreadystatechange = function () {

    if (ajax.status) {

        if (ajax.status == 200 && (ajax.readyState == 4)){
            //To do tasks if any, when upload is completed
        }
    }
}
ajax.upload.addEventListener("progress", function (event) {

    var percent = (event.loaded / event.total) * 100;
    //**percent** variable can be used for modifying the length of your progress bar.
    console.log(percent);

});

ajax.open("POST", 'your file upload link', true);
ajax.send(formData);
//ajax.send is for uploading form data.

Get current user id in ASP.NET Identity 2.0

Just in case you are like me and the Id Field of the User Entity is an Int or something else other than a string,

using Microsoft.AspNet.Identity;

int userId = User.Identity.GetUserId<int>();

will do the trick

Formatting code in Notepad++

NPP+ v7.9.1 with the latest version of XMLTools can't format exported VBA code from Office 2016/2019 Word. It puts all the code on the same line since it strips the CRLF out. Moreover, when you enable "auto validation" it errors out on the first VBA line that is, Attribute VB_Name = "The VBA module name". So any of the xml tool validations apparently can't be used for VBA validation.

PHP Session timeout

    session_cache_expire( 20 );
    session_start(); // NEVER FORGET TO START THE SESSION!!!
    $inactive = 1200; //20 minutes *60
    if(isset($_SESSION['start']) ) {
$session_life = time() - $_SESSION['start'];
if($session_life > $inactive){
    header("Location: user_logout.php");
}
    }
    $_SESSION['start'] = time();

    if($_SESSION['valid_user'] != true){
    header('Location: ../....php');
    }else{  

source: http://www.daniweb.com/web-development/php/threads/124500

how can I enable scrollbars on the WPF Datagrid?

WPF4

<DataGrid AutoGenerateColumns="True" Grid.Column="0" Grid.Row="0"
      ScrollViewer.CanContentScroll="True" 
      ScrollViewer.VerticalScrollBarVisibility="Auto"
      ScrollViewer.HorizontalScrollBarVisibility="Auto">
</DataGrid>

with : <ColumnDefinition Width="350" /> & <RowDefinition Height="300" /> works fine.

Scrollbars don't show with <ColumnDefinition Width="Auto" /> & <RowDefinition Height="300" />.

Also works fine with: <ColumnDefinition Width="*" /> & <RowDefinition Height="300" /> in the case where this is nested within an outer <Grid>.

Encoding as Base64 in Java

I tried with the following code snippet. It worked well. :-)

com.sun.org.apache.xml.internal.security.utils.Base64.encode("The string to encode goes here");

Find files with size in Unix

find . -size +10000k -exec ls -sd {} +

If your version of find won't accept the + notation (which acts rather like xargs does), then you might use (GNU find and xargs, so find probably supports + anyway):

find . -size +10000k -print0 | xargs -0 ls -sd

or you might replace the + with \; (and live with the relative inefficiency of this), or you might live with problems caused by spaces in names and use the portable:

find . -size +10000k -print | xargs ls -sd

The -d on the ls commands ensures that if a directory is ever found (unlikely, but...), then the directory information will be printed, not the files in the directory. And, if you're looking for files more than 1 MB (as a now-deleted comment suggested), you need to adjust the +10000k to 1000k or maybe +1024k, or +2048 (for 512-byte blocks, the default unit for -size). This will list the size and then the file name. You could avoid the need for -d by adding -type f to the find command, of course.

Shortcut to create properties in Visual Studio?

Type "propfull". It is much better to use, and it will generate the property and private variable.

Type "propfull" and then TAB twice.

How to delete all files from a specific folder?

Add the following namespace,

using System.IO;

and use the Directory class to reach on the specific folder:

string[] fileNames = Directory.GetFiles(@"your directory path");
foreach (string fileName in fileNames)
    File.Delete(fileName);

Error in strings.xml file in Android

Solution

Apostrophes in the strings.xml should be written as

\'


Example

In my case I had an error with this string in my strings.xml and I fixed it.

<item>Most arguments can be ended with three words, "I don\'t care".</item>

Here you see my app builds properly with that code.

enter image description here

Here is the actual string in my app.

enter image description here

In Git, what is the difference between origin/master vs origin master?

There are actually three things here: origin master is two separate things, and origin/master is one thing. Three things total.

Two branches:

  • master is a local branch
  • origin/master is a remote branch (which is a local copy of the branch named "master" on the remote named "origin")

One remote:

  • origin is a remote

Example: pull in two steps

Since origin/master is a branch, you can merge it. Here's a pull in two steps:

Step one, fetch master from the remote origin. The master branch on origin will be fetched and the local copy will be named origin/master.

git fetch origin master

Then you merge origin/master into master.

git merge origin/master

Then you can push your new changes in master back to origin:

git push origin master

More examples

You can fetch multiple branches by name...

git fetch origin master stable oldstable

You can merge multiple branches...

git merge origin/master hotfix-2275 hotfix-2276 hotfix-2290

Text file in VBA: Open/Find Replace/SaveAs/Close File

Just add this line

sFileName = "C:\someotherfilelocation"

right before this line

Open sFileName For Output As iFileNum

The idea is to open and write to a different file than the one you read earlier (C:\filelocation).

If you want to get fancy and show a real "Save As" dialog box, you could do this instead:

sFileName = Application.GetSaveAsFilename()

When does SQLiteOpenHelper onCreate() / onUpgrade() run?

Recheck your query in ur DatabaseHandler/DatabaseManager class(which ever you have took)

How to get Android GPS location

Here's your problem:

int latitude = (int) (location.getLatitude());
int longitude = (int) (location.getLongitude());

Latitude and Longitude are double-values, because they represent the location in degrees.

By casting them to int, you're discarding everything behind the comma, which makes a big difference. See "Decimal Degrees - Wiki"

File input 'accept' attribute - is it useful?

The accept attribute is incredibly useful. It is a hint to browsers to only show files that are allowed for the current input. While it can typically be overridden by users, it helps narrow down the results for users by default, so they can get exactly what they're looking for without having to sift through a hundred different file types.

Usage

Note: These examples were written based on the current specification and may not actually work in all (or any) browsers. The specification may also change in the future, which could break these examples.

_x000D_
_x000D_
h1 { font-size: 1em; margin:1em 0; }_x000D_
h1 ~ h1 { border-top: 1px solid #ccc; padding-top: 1em; }
_x000D_
<h1>Match all image files (image/*)</h1>_x000D_
<p><label>image/* <input type="file" accept="image/*"></label></p>_x000D_
_x000D_
<h1>Match all video files (video/*)</h1>_x000D_
<p><label>video/* <input type="file" accept="video/*"></label></p>_x000D_
_x000D_
<h1>Match all audio files (audio/*)</h1>_x000D_
<p><label>audio/* <input type="file" accept="audio/*"></label></p>_x000D_
_x000D_
<h1>Match all image files (image/*) and files with the extension ".someext"</h1>_x000D_
<p><label>.someext,image/* <input type="file" accept=".someext,image/*"></label></p>_x000D_
_x000D_
<h1>Match all image files (image/*) and video files (video/*)</h1>_x000D_
<p><label>image/*,video/* <input type="file" accept="image/*,video/*"></label></p>
_x000D_
_x000D_
_x000D_

From the HTML Specification (source)

The accept attribute may be specified to provide user agents with a hint of what file types will be accepted.

If specified, the attribute must consist of a set of comma-separated tokens, each of which must be an ASCII case-insensitive match for one of the following:

The string audio/*

  • Indicates that sound files are accepted.

The string video/*

  • Indicates that video files are accepted.

The string image/*

  • Indicates that image files are accepted.

A valid MIME type with no parameters

  • Indicates that files of the specified type are accepted.

A string whose first character is a U+002E FULL STOP character (.)

  • Indicates that files with the specified file extension are accepted.

Open source face recognition for Android

macgyver offers face detection programs via a simple to use API.

The program below takes a reference to a public image and will return an array of the coordinates and dimensions of any faces detected in the image.

https://askmacgyver.com/explore/program/face-location/5w8J9u4z

java.lang.OutOfMemoryError: GC overhead limit exceeded

For the record, we had the same problem today. We fixed it by using this option:

-XX:-UseConcMarkSweepGC

Apparently, this modified the strategy used for garbage collection, which made the issue disappear.

invalid types 'int[int]' for array subscript

int myArray[10][10][10];

should be

int myArray[10][10][10][10];

How to install XCODE in windows 7 platform?

X-code is primarily made for OS-X or iPhone development on Mac systems. Versions for Windows are not available. However this might help!

There is no way to get Xcode on Windows; however you can use a different SDK like Corona instead although it will not use Objective-C (I believe it uses Lua). I have however heard that it is horrible to use.

Source: classroomm.com

Address in mailbox given [] does not comply with RFC 2822, 3.6.2. when email is in a variable

Make sure your email address variable is not blank. Check using

print_r($variable_passed);

Refused to execute script, strict MIME type checking is enabled?

My problem was that I have been putting the CSS files in the scripts definition area just above the end of the Try to check the files spots within your pages

java.net.SocketException: Connection reset

Connection reset simply means that a TCP RST was received. This happens when your peer receives data that it can't process, and there can be various reasons for that.

The simplest is when you close the socket, and then write more data on the output stream. By closing the socket, you told your peer that you are done talking, and it can forget about your connection. When you send more data on that stream anyway, the peer rejects it with an RST to let you know it isn't listening.

In other cases, an intervening firewall or even the remote host itself might "forget" about your TCP connection. This could happen if you don't send any data for a long time (2 hours is a common time-out), or because the peer was rebooted and lost its information about active connections. Sending data on one of these defunct connections will cause a RST too.


Update in response to additional information:

Take a close look at your handling of the SocketTimeoutException. This exception is raised if the configured timeout is exceeded while blocked on a socket operation. The state of the socket itself is not changed when this exception is thrown, but if your exception handler closes the socket, and then tries to write to it, you'll be in a connection reset condition. setSoTimeout() is meant to give you a clean way to break out of a read() operation that might otherwise block forever, without doing dirty things like closing the socket from another thread.

Is true == 1 and false == 0 in JavaScript?

It's true that true and false don't represent any numerical values in Javascript.

In some languages (e.g. C, VB), the boolean values are defined as actual numerical values, so they are just different names for 1 and 0 (or -1 and 0).

In some other languages (e.g. Pascal, C#), there is a distinct boolean type that is not numerical. It's possible to convert between boolean values and numerical values, but it doesn't happen automatically.

Javascript falls in the category that has a distinct boolean type, but on the other hand Javascript is quite keen to convert values between different data types.

For example, eventhough a number is not a boolean, you can use a numeric value where a boolean value is expected. Using if (1) {...} works just as well as if (true) {...}.

When comparing values, like in your example, there is a difference between the == operator and the === operator. The == equality operator happily converts between types to find a match, so 1 == true evaluates to true because true is converted to 1. The === type equality operator doesn't do type conversions, so 1 === true evaluates to false because the values are of different types.

Get selected row item in DataGrid WPF

Just discovered this one after i tried Fara's answer but it didn't work on my project. Just drag the column from the Data Sources window, and drop to the Label or TextBox.

Algorithm for Determining Tic Tac Toe Game Over

If you have boarder field 5*5 for examle, I used next method of checking:

public static boolean checkWin(char symb) {
  int SIZE = 5;

        for (int i = 0; i < SIZE-1; i++) {
            for (int j = 0; j <SIZE-1 ; j++) {
                //vertical checking
            if (map[0][j] == symb && map[1][j] == symb && map[2][j] == symb && map[3][j] == symb && map[4][j] == symb) return true;      // j=0
            }
            //horisontal checking
            if(map[i][0] == symb && map[i][1] == symb && map[i][2] == symb && map[i][3] == symb && map[i][4] == symb) return true;  // i=0
        }
        //diagonal checking (5*5)
        if (map[0][0] == symb && map[1][1] == symb && map[2][2] == symb && map[3][3] == symb && map[4][4] == symb) return true;
        if (map[4][0] == symb && map[3][1] == symb && map[2][2] == symb && map[1][3] == symb && map[0][4] == symb) return true;

        return false; 
        }

I think, it's more clear, but probably is not the most optimal way.

How to get GET (query string) variables in Express.js on Node.js?

You should be able to do something like this:

var http = require('http');
var url  = require('url');

http.createServer(function(req,res){
    var url_parts = url.parse(req.url, true);
    var query = url_parts.query;

    console.log(query); //{Object}

    res.end("End")
})

Excel VBA - select multiple columns not in sequential order

Range("A:B,D:E,G:H").Select can help

Edit note: I just saw you have used different column sequence, I have updated my answer

How to switch text case in visual studio code

I've written a Visual Studio Code extension for changing case (not only upper case, many other options): https://github.com/wmaurer/vscode-change-case

To map the upper case command to a keybinding (e.g. Ctrl+T U), click File -> Preferences -> Keyboard shortcuts, and insert the following into the json config:

{
  "key": "ctrl+t u",
  "command": "extension.changeCase.upper",
  "when": "editorTextFocus"
}




EDIT:

With the November 2016 (release notes) update of VSCode, there is built-in support for converting to upper case and lower case via the commands editor.action.transformToUppercase and editor.action.transformToLowercase. These don't have default keybindings.

The change-case extension is still useful for other text transformations, e.g. camelCase, PascalCase, snake-case, etc.

Creating Unicode character from its number

(ANSWER IS IN DOT NET 4.5 and in java, there must be a similar approach exist)

I am from West Bengal in INDIA. As I understand your problem is ... You want to produce similar to ' ? ' (It is a letter in Bengali language) which has Unicode HEX : 0X0985.

Now if you know this value in respect of your language then how will you produce that language specific Unicode symbol right ?

In Dot Net it is as simple as this :

int c = 0X0985;
string x = Char.ConvertFromUtf32(c);

Now x is your answer. But this is HEX by HEX convert and sentence to sentence conversion is a work for researchers :P

What are major differences between C# and Java?

Another good resource is http://www.javacamp.org/javavscsharp/ This site enumerates many examples that ilustrate almost all the differences between these two programming languages.

About the Attributes, Java has Annotations, that work almost the same way.

How can building a heap be O(n) time complexity?

Successive insertions can be described by:

T = O(log(1) + log(2) + .. + log(n)) = O(log(n!))

By starling approximation, n! =~ O(n^(n + O(1))), therefore T =~ O(nlog(n))

Hope this helps, the optimal way O(n) is using the build heap algorithm for a given set (ordering doesn't matter).

Getting "type or namespace name could not be found" but everything seems ok?

I got this error trying to make a build with a Visual Studio Team Services build running on my local machine as an agent.

It worked in my regular workspace just fine and I was able to open the SLN file within the agent folder locally and everything compiled ok.

The DLL in question was stored within the project as Lib/MyDLL.DLL and references with this in the csproj file:

<Reference Include="MYDLL, Version=2009.0.0.0, Culture=neutral, PublicKeyToken=b734e31dca085caa">
  <SpecificVersion>False</SpecificVersion>
  <HintPath>Lib\MYDLL.dll</HintPath>
</Reference>

It turned out it literally just wasn't finding the file despite the hint path. I think maybe msbuild was looking relative to the SLN file instead of the project file.

In any case if the message you get is Could not resolve this reference. Could not locate the assembly then make sure that the DLL is in an accessible location to msbuild.

I kind of cheated and found a message that said Considered "Reference\bin\xxx.dll" and just copied the dlls into there instead.

Check if value exists in dataTable?

You can use LINQ-to-DataSet with Enumerable.Any:

String author = "John Grisham";
bool contains = tbl.AsEnumerable().Any(row => author == row.Field<String>("Author"));

Another approach is to use DataTable.Select:

DataRow[] foundAuthors = tbl.Select("Author = '" + searchAuthor + "'");
if(foundAuthors.Length != 0)
{
    // do something...
}

Q: what if we do not know the columns Headers and we want to find if any cell value PEPSI exist in any rows'c columns? I can loop it all to find out but is there a better way? –

Yes, you can use this query:

DataColumn[] columns = tbl.Columns.Cast<DataColumn>().ToArray();
bool anyFieldContainsPepsi = tbl.AsEnumerable()
    .Any(row => columns.Any(col => row[col].ToString() == "PEPSI"));

Host 'xxx.xx.xxx.xxx' is not allowed to connect to this MySQL server

Just perform the following steps:

1a) Connect to mysql (via localhost)

mysql -uroot -p

1b) If the mysql server is running in Kubernetes (K8s) and being accessed via a NodePort

kubectl exec -it [pod-name] -- /bin/bash
mysql -uroot -p
  1. Create user

    CREATE USER 'user'@'%' IDENTIFIED BY 'password';

  2. Grant permissions

    GRANT ALL PRIVILEGES ON *.* TO 'user'@'%' WITH GRANT OPTION;

  3. Flush privileges

    FLUSH PRIVILEGES;

Hide div by default and show it on click with bootstrap

Just add water style="display:none"; to the <div>

Fiddles I say: http://jsfiddle.net/krY56/13/

jQuery:

function toggler(divId) {
    $("#" + divId).toggle();
}

Preferred to have a CSS Class .hidden

.hidden {
     display:none;
}

Purpose of returning by const value?

It could be used as a wrapper function for returning a reference to a private constant data type. For example in a linked list you have the constants tail and head, and if you want to determine if a node is a tail or head node, then you can compare it with the value returned by that function.

Though any optimizer would most likely optimize it out anyway...

Boto3 Error: botocore.exceptions.NoCredentialsError: Unable to locate credentials

Exporting the credential also work, In linux:

export AWS_SECRET_ACCESS_KEY="XXXXXXXXXXXX"
export AWS_ACCESS_KEY_ID="XXXXXXXXXXX"

typecast string to integer - Postgres

The only way I succeed to not having an error because of NULL, or special characters or empty string is by doing this:

SELECT REGEXP_REPLACE(COALESCE(<column>::character varying, '0'), '[^0-9]*' ,'0')::integer FROM table

Sorted collection in Java

The most efficient way to implement a sorted list like you want would be to implement an indexable skiplist as in here: Wikipedia: Indexable skiplist. It would allow to have inserts/removals in O(log(n)) and would allow to have indexed access at the same time. And it would also allow duplicates.

Skiplist is a pretty interesting and, I would say, underrated data structure. Unfortunately there is no indexed skiplist implementation in Java base library, but you can use one of open source implementations or implement it yourself. There are regular Skiplist implementations like ConcurrentSkipListSet and ConcurrentSkipListMap

c# Image resizing to different size while preserving aspect ratio

public static void resizeImage_n_save(Stream sourcePath, string targetPath, int requiredSize)
    {
        using (var image = System.Drawing.Image.FromStream(sourcePath))
        {
            double ratio = 0;

            var newWidth = 0;
            var newHeight = 0;
            double w = Convert.ToInt32(image.Width);
            double h = Convert.ToInt32(image.Height);
            if (w > h)
            {
                ratio = h / w * 100;
                newWidth = requiredSize;
                newHeight = Convert.ToInt32(requiredSize * ratio / 100);
            }
            else
            {
                ratio = w / h * 100;
                newHeight = requiredSize;
                newWidth = Convert.ToInt32(requiredSize * ratio / 100);
            }

            //   var newWidth = (int)(image.Width * scaleFactor);
            // var newHeight = (int)(image.Height * scaleFactor);
            var thumbnailImg = new Bitmap(newWidth, newHeight);
            var thumbGraph = Graphics.FromImage(thumbnailImg);
            thumbGraph.CompositingQuality = CompositingQuality.HighQuality;
            thumbGraph.SmoothingMode = SmoothingMode.HighQuality;
            thumbGraph.InterpolationMode = InterpolationMode.HighQualityBicubic;
            var imageRectangle = new Rectangle(0, 0, newWidth, newHeight);

            thumbGraph.DrawImage(image, imageRectangle);
            thumbnailImg.Save(targetPath, image.RawFormat);

            //var img = FixedSize(image, requiredSize, requiredSize);
            //img.Save(targetPath, image.RawFormat);

        }
    }

How to convert a timezone aware string to datetime in Python without dateutil?

As of Python 3.7, datetime.datetime.fromisoformat() can handle your format:

>>> import datetime
>>> datetime.datetime.fromisoformat('2012-11-01T04:16:13-04:00')
datetime.datetime(2012, 11, 1, 4, 16, 13, tzinfo=datetime.timezone(datetime.timedelta(days=-1, seconds=72000)))

In older Python versions you can't, not without a whole lot of painstaking manual timezone defining.

Python does not include a timezone database, because it would be outdated too quickly. Instead, Python relies on external libraries, which can have a far faster release cycle, to provide properly configured timezones for you.

As a side-effect, this means that timezone parsing also needs to be an external library. If dateutil is too heavy-weight for you, use iso8601 instead, it'll parse your specific format just fine:

>>> import iso8601
>>> iso8601.parse_date('2012-11-01T04:16:13-04:00')
datetime.datetime(2012, 11, 1, 4, 16, 13, tzinfo=<FixedOffset '-04:00'>)

iso8601 is a whopping 4KB small. Compare that tot python-dateutil's 148KB.

As of Python 3.2 Python can handle simple offset-based timezones, and %z will parse -hhmm and +hhmm timezone offsets in a timestamp. That means that for a ISO 8601 timestamp you'd have to remove the : in the timezone:

>>> from datetime import datetime
>>> iso_ts = '2012-11-01T04:16:13-04:00'
>>> datetime.strptime(''.join(iso_ts.rsplit(':', 1)), '%Y-%m-%dT%H:%M:%S%z')
datetime.datetime(2012, 11, 1, 4, 16, 13, tzinfo=datetime.timezone(datetime.timedelta(-1, 72000)))

The lack of proper ISO 8601 parsing is being tracked in Python issue 15873.

How do I put hint in a asp:textbox

The placeholder attribute

You're looking for the placeholder attribute. Use it like any other attribute inside your ASP.net control:

<asp:textbox id="txtWithHint" placeholder="hint" runat="server"/>

Don't bother about your IDE (i.e. Visual Studio) maybe not knowing the attribute. Attributes which are not registered with ASP.net are passed through and rendered as is. So the above code (basically) renders to:

<input type="text" placeholder="hint"/>

Using placeholder in resources

A fine way of applying the hint to the control is using resources. This way you may have localized hints. Let's say you have an index.aspx file, your App_LocalResources/index.aspx.resx file contains

<data name="WithHint.placeholder">
    <value>hint</value>
</data>

and your control looks like

<asp:textbox id="txtWithHint" meta:resourcekey="WithHint" runat="server"/>

the rendered result will look the same as the one in the chapter above.

Add attribute in code behind

Like any other attribute you can add the placeholder to the AttributeCollection:

txtWithHint.Attributes.Add("placeholder", "hint");

How to upgrade Git to latest version on macOS?

the simplest way I found so far is from git official website. It just computed dependencies and downloaded all of the required libraries/tools

http://git-scm.com/book/en/Getting-Started-Installing-Git

The other major way is to install Git via MacPorts (http://www.macports.org). If you have MacPorts installed, install Git via

$ sudo port install git-core +svn +doc +bash_completion +gitweb

MS Access VBA: Sending an email through Outlook

Add a reference to the Outlook object model in the Visual Basic editor. Then you can use the code below to send an email using outlook.

Sub sendOutlookEmail()
Dim oApp As Outlook.Application
Dim oMail As MailItem
Set oApp = CreateObject("Outlook.application")

Set oMail = oApp.CreateItem(olMailItem)
oMail.Body = "Body of the email"
oMail.Subject = "Test Subject"
oMail.To = "[email protected]"
oMail.Send
Set oMail = Nothing
Set oApp = Nothing


End Sub

What operator is <> in VBA

Not Equal To


Before C came along and popularized !=, languages tended to use <> for not equal to.

At least, the various dialects of Basic did, and they predate C.

An even older and more unusual case is Fortran, which uses .NE., as in X .NE. Y.

How do I print colored output with Python 3?

I would like to show you about how to color code. There is also a game to it if you would like to play it down below. Copy and paste if you would like and make sure to have a good day everyone! Also, this is for Python 3, not 2. ( Game )

   # The Color Game!
# Thank you for playing this game.
# Hope you enjoy and please do not copy it. Thank you!

#

import colorama
from colorama import Fore
score = 0

def Check_Answer(answer):
    if (answer == "no"):
        print('correct')
        return True
    else:
        print('wrong')

answer = input((Fore.RED + "This is green."))
if Check_Answer(answer) == True:
    score = score + 1
else:
    pass

answer = input((Fore.BLACK + "This is red."))
if Check_Answer(answer) == True:
    score = score + 1
else:
    pass

answer = input((Fore.BLUE + "This is black."))

if Check_Answer(answer) == True:
    score = score + 1
else:
    pass

print('Your Score is ', score)

Now for the color coding. It also comes with a list of colors YOU can try.

# Here is how to color code in Python 3!
# Some featured color codes are : RED, BLUE, GREEN, YELLOW, OR WHITE. I don't think purple or pink are not out yet.
# Here is how to do it. (Example is down below!)

import colorama
from colorama import Fore
print(Fore.RED + "This is red..")

Protect .NET code from reverse engineering?

If it's written in .NET and compiled to CIL, it can be reflected. If security is a concern and obfuscation is to be avoided, then I recommend writing your application using a non-managed language, which is, by nature, harder to reverse engineer.

Set focus on textbox in WPF

Another possible solution is to use FocusBehavior provided by free DevExpress MVVM Framework:

<TextBox Text="This control is focused on startup">
    <dxmvvm:Interaction.Behaviors>
        <dxmvvm:FocusBehavior/>
    </dxmvvm:Interaction.Behaviors>
</TextBox>

It allows you to focus a control when it's loaded, when a certain event is raised or a property is changed.

Iterating through a List Object in JSP

another example with just scriplets, when iterating through an ArrayList that contains Maps.

<%   
java.util.List<java.util.Map<String,String>> employees=(java.util.List<java.util.Map<String, String>>)request.getAttribute("employees");    

for (java.util.Map employee: employees) {
%>
<tr>
<td><input value="<%=employee.get("fullName") %>"/></td>    
</tr>
...
<%}%>

What is the most efficient way to create HTML elements using jQuery?

Question:

What is the most efficient way to create HTML elements using jQuery?

Answer:

Since it's about jQuery then I think it's better to use this (clean) approach (you are using)

$('<div/>', {
    'id':'myDiv',
    'class':'myClass',
    'text':'Text Only',
}).on('click', function(){
    alert(this.id); // myDiv
}).appendTo('body');

DEMO.

This way, you can even use event handlers for the specific element like

$('<div/>', {
    'id':'myDiv',
    'class':'myClass',
    'style':'cursor:pointer;font-weight:bold;',
    'html':'<span>For HTML</span>',
    'click':function(){ alert(this.id) },
    'mouseenter':function(){ $(this).css('color', 'red'); },
    'mouseleave':function(){ $(this).css('color', 'black'); }
}).appendTo('body');

DEMO.

But when you are dealing with lots of dynamic elements, you should avoid adding event handlers in particular element, instead, you should use a delegated event handler, like

$(document).on('click', '.myClass', function(){
    alert(this.innerHTML);
});

var i=1;
for(;i<=200;i++){
    $('<div/>', {
        'class':'myClass',
        'html':'<span>Element'+i+'</span>'
    }).appendTo('body');
}

DEMO.

So, if you create and append hundreds of elements with same class, i.e. (myClass) then less memory will be consumed for event handling, because only one handler will be there to do the job for all dynamically inserted elements.

Update : Since we can use following approach to create a dynamic element

$('<input/>', {
    'type': 'Text',
    'value':'Some Text',
    'size': '30'
}).appendTo("body");

But the size attribute can't be set using this approach using jQuery-1.8.0 or later and here is an old bug report, look at this example using jQuery-1.7.2 which shows that size attribute is set to 30 using above example but using same approach we can't set size attribute using jQuery-1.8.3, here is a non-working fiddle. So, to set the size attribute, we can use following approach

$('<input/>', {
    'type': 'Text',
    'value':'Some Text',
    attr: { size: "30" }
}).appendTo("body");

Or this one

$('<input/>', {
    'type': 'Text',
    'value':'Some Text',
    prop: { size: "30" }
}).appendTo("body");

We can pass attr/prop as a child object but it works in jQuery-1.8.0 and later versions check this example but it won't work in jQuery-1.7.2 or earlier (not tested in all earlier versions).

BTW, taken from jQuery bug report

There are several solutions. The first is to not use it at all, since it doesn't save you any space and this improves the clarity of the code:

They advised to use following approach (works in earlier ones as well, tested in 1.6.4)

$('<input/>')
.attr( { type:'text', size:50, autofocus:1 } )
.val("Some text").appendTo("body");

So, it is better to use this approach, IMO. This update is made after I read/found this answer and in this answer shows that if you use 'Size'(capital S) instead of 'size' then it will just work fine, even in version-2.0.2

$('<input>', {
    'type' : 'text',
    'Size' : '50', // size won't work
    'autofocus' : 'true'
}).appendTo('body');

Also read about prop, because there is a difference, Attributes vs. Properties, it varies through versions.

inserting characters at the start and end of a string

Strings are immutable so you can't insert characters into an existing string. You have to create a new string. You can use string concatenation to do what you want:

yourstring = "L" + yourstring + "LL"

Note that you can also create a string with n Ls by using multiplication:

m = 1
n = 2
yourstring = ("L" * m) + yourstring + ("L" * n)

How to show Bootstrap table with sort icon

BOOTSTRAP 4

you can use a combination of

  • fa-chevron-down, fa-chevron-up

  • fa-sort-down, fa-sort-up

<th class="text-center">
    <div class="btn-group" role="group">
        <button type="button" class="btn btn-xs btn-link py-0 pl-0 pr-1">
             Some Text OR icon
        </button>
        <div class="btn-group-vertical">
            <a href="?sort=asc" class="btn btn-xs btn-link p-0">
                <i class="fas fa-sort-up"></i>
            </a>
            <a href="?sort=desc" class="btn btn-xs btn-link p-0">
                <i class="fas fa-sort-down"></i>
            </a>
        </div>
    </div>
</th>

How to check if object property exists with a variable holding the property name?

A much more secure way to check if property exists on the object is to use empty object or object prototype to call hasOwnProperty()

var foo = {
  hasOwnProperty: function() {
    return false;
  },
  bar: 'Here be dragons'
};

foo.hasOwnProperty('bar'); // always returns false

// Use another Object's hasOwnProperty and call it with 'this' set to foo
({}).hasOwnProperty.call(foo, 'bar'); // true

// It's also possible to use the hasOwnProperty property from the Object
// prototype for this purpose
Object.prototype.hasOwnProperty.call(foo, 'bar'); // true

Reference from MDN Web Docs - Object.prototype.hasOwnProperty()

Switching to landscape mode in Android Emulator

Not sure about your question - "sideways" is the same as "landscape".

If you mean how to switch during runtime:

  • Switch to previous layout orientation (for example, portrait, landscape): KEYPAD_7, Ctrl + F11
  • Switch to next layout orientation (for example, portrait, landscape): KEYPAD_9, Ctrl + F12

From docs.

MySQL does not start when upgrading OSX to Yosemite or El Capitan

In my case I fixed it doing a little permission change:

sudo chown -R _mysql:_mysql /usr/local/var/mysql
sudo mysql.server start

I hope it helps somebody else...

Note: As per Mert Mertin comment:

For el capitan, it is sudo chown -R _mysql:_mysql /usr/local/var/mysql

Where can I find MySQL logs in phpMyAdmin?

I had the same problem of @rutherford, today the new phpMyAdmin's 3.4.11.1 GUI is different, so I figure out it's better if someone improves the answers with updated info.

Full mysql logs can be found in:

"Status"->"Binary Log"

This is the answer, doesn't matter if you're using MAMP, XAMPP, LAMP, etc.

How to escape JSON string?

I nice one-liner, used JsonConvert as others have but added substring to remove the added quotes and backslash.

 var escapedJsonString = JsonConvert.ToString(JsonString).Substring(1, JsonString.Length - 2);

Error - trustAnchors parameter must be non-empty

On Ubuntu 18.04 the root cause is a conflict between openjdk-11-jdk (which is default) and other packages depending on it. It has already been fixed in Debian and will be included in Ubuntu shortly. Meanwhile the simplest workaround is to demote your java to version 8. Other solutions employing ca-certificates-java are much more complicated.

First remove conflicting packages:

sudo apt-get remove --purge openjdk* java-common default-jdk
sudo apt-get autoremove --purge

Check whether you successfully removed all related packages by:

sudo update-alternatives --config java

The system shall prompt you there is no Java available to config, otherwise this workaround fails.

Then reinstall required packages:

sudo apt-get install openjdk-8-jdk

Sending email in .NET through Gmail

The above answer doesn't work. You have to set DeliveryMethod = SmtpDeliveryMethod.Network or it will come back with a "client was not authenticated" error. Also it's always a good idea to put a timeout.

Revised code:

using System.Net.Mail;
using System.Net;

var fromAddress = new MailAddress("[email protected]", "From Name");
var toAddress = new MailAddress("[email protected]", "To Name");
const string fromPassword = "password";
const string subject = "test";
const string body = "Hey now!!";

var smtp = new SmtpClient
{
    Host = "smtp.gmail.com",
    Port = 587,
    EnableSsl = true,
    DeliveryMethod = SmtpDeliveryMethod.Network,
    Credentials = new NetworkCredential(fromAddress.Address, fromPassword),
    Timeout = 20000
};
using (var message = new MailMessage(fromAddress, toAddress)
{
    Subject = subject,
    Body = body
})
{
    smtp.Send(message);
}

A url resource that is a dot (%2E)

It's actually not really clearly stated in the standard (RFC 3986) whether a percent-encoded version of . or .. is supposed to have the same this-folder/up-a-folder meaning as the unescaped version. Section 3.3 only talks about “The path segments . and ..”, without clarifying whether they match . and .. before or after pct-encoding.

Personally I find Firefox's interpretation that %2E does not mean . most practical, but unfortunately all the other browsers disagree. This would mean that you can't have a path component containing only . or ...

I think the only possible suggestion is “don't do that”! There are other path components that are troublesome too, typically due to server limitations: %2F, %00 and %5C sequences in paths may also be blocked by some web servers, and the empty path segment can also cause problems. So in general it's not possible to fit all possible byte sequences into a path component.

Equivalent of LIMIT for DB2

Try this

SELECT * FROM
    (
        SELECT T.*, ROW_NUMBER() OVER() R FROM TABLE T
    )
    WHERE R BETWEEN 10000 AND 20000

jQuery keypress() event not firing?

e.which doesn't work in IE try e.keyCode, also you probably want to use keydown() instead of keypress() if you are targeting IE.

See http://unixpapa.com/js/key.html for more information.

Why is null an object and what's the difference between null and undefined?

TLDR

undefined is a primitive value in JavaScript that indicates the implicit absence of a value. Uninitialized variables automatically have this value, and functions without an explicit return statement, return undefined.

null is also a primitive value in JavaScript. It indicates the intentional absence of an object value. null in JavaScript was designed to enable interoperability with Java.

typeof null returns "object" because of a peculiarity in the design of the language, stemming from the demand that JavaScript be interoperable with Java. It does not mean null is an instance of an object. It means: given the tree of primitive types in JavaScript, null is part of the "object-type primitive" subtree. This is explained more fully below.

Details

undefined is a primitive value that represents the implicit absence of a value. Note that undefined was not directly accessible until JavaScript 1.3 in 1998. This tells us that null was intended to be the value used by programmers when explicitly indicating the absence of a value. Uninitialized variables automatically have the value undefined. undefined is a one-of-a-kind type in the ECMAScript specification.

null is a primitive value that represents the intentional absence of an object value. null is also a one-of-a-kind type in the ECMAScript specification.

null in JavaScript was designed with a view to enable interoperability with Java, both from a "look" perspective, and from a programatic perspective (eg the LiveConnect Java/JS bridge planned for 1996). Both Brendan Eich and others have since expressed distaste at the inclusion of two "absence of value" values, but in 1995 Eich was under orders to "make [JavaScript] look like Java".

Brendan Eich:

If I didn't have "Make it look like Java" as an order from management, and I had more time (hard to unconfound these two causal factors), then I would have preferred a Self-like "everything's an object" approach: no Boolean, Number, String wrappers. No undefined and null. Sigh.

In order to accommodate Java's concept of null which, due to the strongly-typed nature of Java, can only be assigned to variables typed to a reference type (rather primitives), Eich chose to position the special null value at the top of the object prototype chain (ie. the top of the reference types), and to include the null type as part of the set of "object-type primitives".

The typeof operator was added shortly thereafter in JavaScript 1.1, released on 19th August 1996.

From the V8 blog:

typeof null returns object, and not null, despite null being a type of its own. To understand why, consider that the set of all JavaScript types is divided into two groups:

  1. objects (i.e. the Object type)
  2. primitives (i.e. any non-object value)

As such, null means “no object value”, whereas undefined means “no value”.

enter image description here

Following this line of thought, Brendan Eich designed JavaScript to make typeof return 'object' for all values on the right-hand side, i.e. all objects and null values, in the spirit of Java. That’s why typeof null === 'object' despite the spec having a separate null type.

enter image description here

So Eich designed the heirarchy of primitive types to enable interoperability with Java. This led to him positioning null along with the "object-type primitives" on the heirarchy. To refelct this, when typeof was added to the language shortly thereafter, he chose typeof null to return "object".

The surprise expressed by JavaScript developers at typeof null === "object" is the result of an impedance mismatch (or abstraction leak) between a weakly-typed language (JavaScript) that has both null and undefined, and another, strongly-typed language (Java) that only has null, and in which null is strictly defined to refer to a reference type (not a primitive type).

Note that this is all logical, reasonable and defensible. typeof null === "object" is not a bug, but a second-order effect of having to accommodate Java interoperability.

A number of imperfect backwards rationalisations and/or conventions have emerged, including that undefined indicates implicit absence of a value, and that null indicates intentional absence of a value; or that undefined is the absence of a value, and null is specifically the absence of an object value.

A relevant conversation with Brendan Eich, screenshotted for posterity:

enter image description here

Generate MD5 hash string with T-SQL

declare @hash nvarchar(50)
--declare @hash varchar(50)

set @hash = '1111111-2;20190110143334;001'  -- result a5cd84bfc56e245bbf81210f05b7f65f
declare @value varbinary(max);
set @value = convert(varbinary(max),@hash);


select  
 SUBSTRING(sys.fn_sqlvarbasetostr(HASHBYTES('MD5', '1111111-2;20190110143334;001')),3,32) as 'OK'
,SUBSTRING(sys.fn_sqlvarbasetostr(HASHBYTES('MD5', @hash)),3,32) as 'ERROR_01'
,SUBSTRING(sys.fn_sqlvarbasetostr(HASHBYTES('MD5',convert(varbinary(max),@hash))),3,32) as 'ERROR_02'
,SUBSTRING(sys.fn_sqlvarbasetostr(sys.fn_repl_hash_binary(convert(varbinary(max),@hash))),3,32)
,SUBSTRING(sys.fn_sqlvarbasetostr(master.sys.fn_repl_hash_binary(@value)),3,32)

Responding with a JSON object in Node.js (converting object/array to JSON string)

var objToJson = { };
objToJson.response = response;
response.write(JSON.stringify(objToJson));

If you alert(JSON.stringify(objToJson)) you will get {"response":"value"}

how to fix groovy.lang.MissingMethodException: No signature of method:

In my case it was simply that I had a variable named the same as a function.

Example:

def cleanCache = functionReturningABoolean()

if( cleanCache ){
    echo "Clean cache option is true, do not uninstall previous features / urls"
    uninstallCmd = ""
    
    // and we call the cleanCache method
    cleanCache(userId, serverName)
}
...

and later in my code I have the function:

def cleanCache(user, server){

 //some operations to the server

}

Apparently the Groovy language does not support this (but other languages like Java does). I just renamed my function to executeCleanCache and it works perfectly (or you can also rename your variable whatever option you prefer).

How to find char in string and get all the indexes?

This is because str.index(ch) will return the index where ch occurs the first time. Try:

def find(s, ch):
    return [i for i, ltr in enumerate(s) if ltr == ch]

This will return a list of all indexes you need.

P.S. Hugh's answer shows a generator function (it makes a difference if the list of indexes can get large). This function can also be adjusted by changing [] to ().

cannot make a static reference to the non-static field

the lines

account.withdraw(balance, 2500);
account.deposit(balance, 3000);

you might want to make withdraw and deposit non-static and let it modify the balance

public void withdraw(double withdrawAmount) {
    balance = balance - withdrawAmount;
}

public void deposit(double depositAmount) {
    balance = balance + depositAmount;
}   

and remove the balance parameter from the call

Compare dates in MySQL

That is SQL Server syntax for converting a date to a string. In MySQL you can use the DATE function to extract the date from a datetime:

SELECT *
FROM players
WHERE DATE(us_reg_date) BETWEEN '2000-07-05' AND '2011-11-10'

But if you want to take advantage of an index on the column us_reg_date you might want to try this instead:

SELECT *
FROM players
WHERE us_reg_date >= '2000-07-05'
  AND us_reg_date < '2011-11-10' + interval 1 day

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

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

DB2 SQL Error: SQLCODE=-206, SQLSTATE=42703, SQLERRMC=[THE_UNDEFINED_COLUMN_OR_PARAMETER_NAME], DRIVER=4.8.87

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

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

http://www.coderanch.com/t/515475/JDBC/databases/sql-insert-statement-giving-sqlcode

Javascript/DOM: How to remove all events of a DOM object?

This will remove all listeners from children but will be slow for large pages. Brutally simple to write.

element.outerHTML = element.outerHTML;

Why should we NOT use sys.setdefaultencoding("utf-8") in a py script?

tl;dr

The answer is NEVER! (unless you really know what you're doing)

9/10 times the solution can be resolved with a proper understanding of encoding/decoding.

1/10 people have an incorrectly defined locale or environment and need to set:

PYTHONIOENCODING="UTF-8"  

in their environment to fix console printing problems.

What does it do?

sys.setdefaultencoding("utf-8") (struck through to avoid re-use) changes the default encoding/decoding used whenever Python 2.x needs to convert a Unicode() to a str() (and vice-versa) and the encoding is not given. I.e:

str(u"\u20AC")
unicode("€")
"{}".format(u"\u20AC") 

In Python 2.x, the default encoding is set to ASCII and the above examples will fail with:

UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 0: ordinal not in range(128)

(My console is configured as UTF-8, so "€" = '\xe2\x82\xac', hence exception on \xe2)

or

UnicodeEncodeError: 'ascii' codec can't encode character u'\u20ac' in position 0: ordinal not in range(128)

sys.setdefaultencoding("utf-8") will allow these to work for me, but won't necessarily work for people who don't use UTF-8. The default of ASCII ensures that assumptions of encoding are not baked into code

Console

sys.setdefaultencoding("utf-8") also has a side effect of appearing to fix sys.stdout.encoding, used when printing characters to the console. Python uses the user's locale (Linux/OS X/Un*x) or codepage (Windows) to set this. Occasionally, a user's locale is broken and just requires PYTHONIOENCODING to fix the console encoding.

Example:

$ export LANG=en_GB.gibberish
$ python
>>> import sys
>>> sys.stdout.encoding
'ANSI_X3.4-1968'
>>> print u"\u20AC"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeEncodeError: 'ascii' codec can't encode character u'\u20ac' in position 0: ordinal not in range(128)
>>> exit()

$ PYTHONIOENCODING=UTF-8 python
>>> import sys
>>> sys.stdout.encoding
'UTF-8'
>>> print u"\u20AC"
€

What's so bad with sys.setdefaultencoding("utf-8")?

People have been developing against Python 2.x for 16 years on the understanding that the default encoding is ASCII. UnicodeError exception handling methods have been written to handle string to Unicode conversions on strings that are found to contain non-ASCII.

From https://anonbadger.wordpress.com/2015/06/16/why-sys-setdefaultencoding-will-break-code/

def welcome_message(byte_string):
    try:
        return u"%s runs your business" % byte_string
    except UnicodeError:
        return u"%s runs your business" % unicode(byte_string,
            encoding=detect_encoding(byte_string))

print(welcome_message(u"Angstrom (Å®)".encode("latin-1"))

Previous to setting defaultencoding this code would be unable to decode the “Å” in the ascii encoding and then would enter the exception handler to guess the encoding and properly turn it into unicode. Printing: Angstrom (Å®) runs your business. Once you’ve set the defaultencoding to utf-8 the code will find that the byte_string can be interpreted as utf-8 and so it will mangle the data and return this instead: Angstrom (U) runs your business.

Changing what should be a constant will have dramatic effects on modules you depend upon. It's better to just fix the data coming in and out of your code.

Example problem

While the setting of defaultencoding to UTF-8 isn't the root cause in the following example, it shows how problems are masked and how, when the input encoding changes, the code breaks in an unobvious way: UnicodeDecodeError: 'utf8' codec can't decode byte 0x80 in position 3131: invalid start byte

Saving images in Python at a very high quality

Okay, I found spencerlyon2's answer working. However, in case anybody would find himself/herself not knowing what to do with that one line, I had to do it this way:

beingsaved = plt.figure()

# Some scatter plots
plt.scatter(X_1_x, X_1_y)
plt.scatter(X_2_x, X_2_y)

beingsaved.savefig('destination_path.eps', format='eps', dpi=1000)

XAMPP keeps showing Dashboard/Welcome Page instead of the Configuration Page

I was also experiencing the same issue. 5.5.24 was the latest version that worked for me. The Apache Friends blog has a post, https://www.apachefriends.org/blog/new_xampp_20150723.html, that mentions the newer versions shipping with the 'Dashboard'.

SHA-1 fingerprint of keystore certificate

In Gnu/Linux

First

You need key.jks, for example in my case this file it's in folder in /Desktop/Keys

/Desktop/Keys/key.jks

Second

cd /usr/lib/jvm/java-1.7.0-openjdk-amd64

Now you need excecute this command

keytool -list -v -keystore /PATH/file.jks -alias YourAlias -storepass *** -keypass ***

remplacing this fields

-keystore
-alias
-storepass
-keypass

For example

 keytool -list -v -keystore /home/david/Desktop/Keys/key.jks -alias MyAlias -storepass 456 -keypass 123

enter image description here

Good Luck!!

HTML table with fixed headers and a fixed column?

If what you want is to have the headers stay put while the data in the table scrolls vertically, you should implement a <tbody> styled with "overflow-y: auto" like this:

<table>
  <thead>
    <tr>
      <th>Header1</th>
       . . . 
    </tr>
   </thead>
   <tbody style="height: 300px; overflow-y: auto"> 
     <tr>
       . . .
     </tr>
     . . .
   </tbody>
 </table>

If the <tbody> content grows taller than the desired height, it will start scrolling. However, the headers will stay fixed at the top regardless of the scroll position.

<SELECT multiple> - how to allow only one item selected?

If the user should select only one option at once, just remove the "multiple" - make a normal select:

  <select name="mySelect" size="3">
     <option>Foo</option>
     <option>Bar</option>
     <option>Foo Bar</option>
     <option>Bar Foo</option>
  </select>

Fiddle

Deleting an element from an array in PHP

  // Our initial array
  $arr = array("blue", "green", "red", "yellow", "green", "orange", "yellow", "indigo", "red");
  print_r($arr);

  // Remove the elements who's values are yellow or red
  $arr = array_diff($arr, array("yellow", "red"));
  print_r($arr);

This is the output from the code above:

Array
(
    [0] => blue
    [1] => green
    [2] => red
    [3] => yellow
    [4] => green
    [5] => orange
    [6] => yellow
    [7] => indigo
    [8] => red
)

Array
(
    [0] => blue
    [1] => green
    [4] => green
    [5] => orange
    [7] => indigo
)

Now, array_values() will reindex a numerical array nicely, but it will remove all key strings from the array and replace them with numbers. If you need to preserve the key names (strings), or reindex the array if all keys are numerical, use array_merge():

$arr = array_merge(array_diff($arr, array("yellow", "red")));
print_r($arr);

Outputs

Array
(
    [0] => blue
    [1] => green
    [2] => green
    [3] => orange
    [4] => indigo
)

Are there pointers in php?

PHP passes Arrays and Objects by reference (pointers). If you want to pass a normal variable Ex. $var = 'boo'; then use $boo = &$var;.

jquery multiple checkboxes array

You can use $.map() (or even the .map() function that operates on a jQuery object) to get an array of checked values. The unary (+) operator will cast the string to a number

var arr = $.map($('input:checkbox:checked'), function(e,i) {
    return +e.value;
});

console.log(arr);

Here's an example

Twitter Bootstrap: div in container with 100% height

Update 2019

In Bootstrap 4, flexbox can be used to get a full height layout that fills the remaining space.

First of all, the container (parent) needs to be full height:

Option 1_ Add a class for min-height: 100%;. Remember that min-height will only work if the parent has a defined height:

html, body {
  height: 100%;
}

.min-100 {
    min-height: 100%;
}

https://codeply.com/go/dTaVyMah1U

Option 2_ Use vh units:

.vh-100 {
    min-height: 100vh;
}

https://codeply.com/go/kMahVdZyGj

Also of Bootstrap 4.1, the vh-100 and min-vh-100 classes are included in Bootstrap so there is no need to for the extra CSS

Then, use flexbox direction column d-flex flex-column on the container, and flex-grow-1 on any child divs (ie: row) that you want to fill the remaining height.

Also see:
Bootstrap 4 Navbar and content fill height flexbox
Bootstrap - Fill fluid container between header and footer
How to make the row stretch remaining height

Stylesheet not updating

This may not have been the OP's problem, but I had the same problem and solved it by flushing then disabling Supercache on my cpanel. Perhaps some other newbies like myself won't know that many hosting providers cache CSS and some other static files, and these cached old versions of CSS files will persist in the cloud for hours after you edit the file on your server. If your site serves up old versions of CSS files after you edit them, and you're certain you've cleared your browser cache, and you don't know whether your host is caching stuff, check that first before you try any other more complicated suggestions.

Returning a regex match in VBA (excel)

You need to access the matches in order to get at the SDI number. Here is a function that will do it (assuming there is only 1 SDI number per cell).

For the regex, I used "sdi followed by a space and one or more numbers". You had "sdi followed by a space and zero or more numbers". You can simply change the + to * in my pattern to go back to what you had.

Function ExtractSDI(ByVal text As String) As String

Dim result As String
Dim allMatches As Object
Dim RE As Object
Set RE = CreateObject("vbscript.regexp")

RE.pattern = "(sdi \d+)"
RE.Global = True
RE.IgnoreCase = True
Set allMatches = RE.Execute(text)

If allMatches.count <> 0 Then
    result = allMatches.Item(0).submatches.Item(0)
End If

ExtractSDI = result

End Function

If a cell may have more than one SDI number you want to extract, here is my RegexExtract function. You can pass in a third paramter to seperate each match (like comma-seperate them), and you manually enter the pattern in the actual function call:

Ex) =RegexExtract(A1, "(sdi \d+)", ", ")

Here is:

Function RegexExtract(ByVal text As String, _
                      ByVal extract_what As String, _
                      Optional seperator As String = "") As String

Dim i As Long, j As Long
Dim result As String
Dim allMatches As Object
Dim RE As Object
Set RE = CreateObject("vbscript.regexp")

RE.pattern = extract_what
RE.Global = True
Set allMatches = RE.Execute(text)

For i = 0 To allMatches.count - 1
    For j = 0 To allMatches.Item(i).submatches.count - 1
        result = result & seperator & allMatches.Item(i).submatches.Item(j)
    Next
Next

If Len(result) <> 0 Then
    result = Right(result, Len(result) - Len(seperator))
End If

RegexExtract = result

End Function

*Please note that I have taken "RE.IgnoreCase = True" out of my RegexExtract, but you could add it back in, or even add it as an optional 4th parameter if you like.

append new row to old csv file python

with open('document.csv','a') as fd:
    fd.write(myCsvRow)

Opening a file with the 'a' parameter allows you to append to the end of the file instead of simply overwriting the existing content. Try that.

Removing multiple keys from a dictionary safely

I'm late to this discussion but for anyone else. A solution may be to create a list of keys as such.

k = ['a','b','c','d']

Then use pop() in a list comprehension, or for loop, to iterate over the keys and pop one at a time as such.

new_dictionary = [dictionary.pop(x, 'n/a') for x in k]

The 'n/a' is in case the key does not exist, a default value needs to be returned.

How to use MySQLdb with Python and Django in OSX 10.6?

I overcame the same problem by installing MySQL-python library using pip. You can see the message displayed on my console when I first changed my database settings in settings.py and executed makemigrations command(The solution is following the below message, just see that).

  (vir_env) admins-MacBook-Pro-3:src admin$ python manage.py makemigrations
Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/admin/Desktop/SetUp1/vir_env/lib/python2.7/site-packages/django/core/management/__init__.py", line 338, in execute_from_command_line
    utility.execute()
  File "/Users/admin/Desktop/SetUp1/vir_env/lib/python2.7/site-packages/django/core/management/__init__.py", line 312, in execute
    django.setup()
  File "/Users/admin/Desktop/SetUp1/vir_env/lib/python2.7/site-packages/django/__init__.py", line 18, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/Users/admin/Desktop/SetUp1/vir_env/lib/python2.7/site-packages/django/apps/registry.py", line 108, in populate
    app_config.import_models(all_models)
  File "/Users/admin/Desktop/SetUp1/vir_env/lib/python2.7/site-packages/django/apps/config.py", line 198, in import_models
    self.models_module = import_module(models_module_name)
  File "/usr/local/Cellar/python/2.7.12_1/Frameworks/Python.framework/Versions/2.7/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
  File "/Users/admin/Desktop/SetUp1/vir_env/lib/python2.7/site-packages/django/contrib/auth/models.py", line 41, in <module>
    class Permission(models.Model):
  File "/Users/admin/Desktop/SetUp1/vir_env/lib/python2.7/site-packages/django/db/models/base.py", line 139, in __new__
    new_class.add_to_class('_meta', Options(meta, **kwargs))
  File "/Users/admin/Desktop/SetUp1/vir_env/lib/python2.7/site-packages/django/db/models/base.py", line 324, in add_to_class
    value.contribute_to_class(cls, name)
  File "/Users/admin/Desktop/SetUp1/vir_env/lib/python2.7/site-packages/django/db/models/options.py", line 250, in contribute_to_class
    self.db_table = truncate_name(self.db_table, connection.ops.max_name_length())
  File "/Users/admin/Desktop/SetUp1/vir_env/lib/python2.7/site-packages/django/db/__init__.py", line 36, in __getattr__
    return getattr(connections[DEFAULT_DB_ALIAS], item)
  File "/Users/admin/Desktop/SetUp1/vir_env/lib/python2.7/site-packages/django/db/utils.py", line 240, in __getitem__
    backend = load_backend(db['ENGINE'])
  File "/Users/admin/Desktop/SetUp1/vir_env/lib/python2.7/site-packages/django/db/utils.py", line 111, in load_backend
    return import_module('%s.base' % backend_name)
  File "/usr/local/Cellar/python/2.7.12_1/Frameworks/Python.framework/Versions/2.7/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
  File "/Users/admin/Desktop/SetUp1/vir_env/lib/python2.7/site-packages/django/db/backends/mysql/base.py", line 27, in <module>
    raise ImproperlyConfigured("Error loading MySQLdb module: %s" % e)
django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: No module named MySQLdb

Finally I overcame this problem as follows:

(vir_env) admins-MacBook-Pro-3:src admin$ pip install MySQLdb
Collecting MySQLdb
  Could not find a version that satisfies the requirement MySQLdb (from versions: )
No matching distribution found for MySQLdb
(vir_env) admins-MacBook-Pro-3:src admin$ pip install MySQL-python
Collecting MySQL-python
  Downloading MySQL-python-1.2.5.zip (108kB)
    100% |¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦| 112kB 364kB/s 
Building wheels for collected packages: MySQL-python
  Running setup.py bdist_wheel for MySQL-python ... done
  Stored in directory: /Users/admin/Library/Caches/pip/wheels/38/a3/89/ec87e092cfb38450fc91a62562055231deb0049a029054dc62
Successfully built MySQL-python
Installing collected packages: MySQL-python
Successfully installed MySQL-python-1.2.5
(vir_env) admins-MacBook-Pro-3:src admin$ python manage.py makemigrations
No changes detected
(vir_env) admins-MacBook-Pro-3:src admin$ python manage.py migrate
Operations to perform:
  Synchronize unmigrated apps: staticfiles, rest_framework, messages, crispy_forms
  Apply all migrations: admin, contenttypes, sessions, auth, PyApp
Synchronizing apps without migrations:
  Creating tables...
    Running deferred SQL...
  Installing custom SQL...
Running migrations:
  Rendering model states... DONE
  Applying PyApp.0001_initial... OK
  Applying PyApp.0002_auto_20170310_0936... OK
  Applying PyApp.0003_auto_20170310_0953... OK
  Applying PyApp.0004_auto_20170310_0954... OK
  Applying PyApp.0005_auto_20170311_0619... OK
  Applying PyApp.0006_auto_20170311_0622... OK
  Applying PyApp.0007_loraevksensor... OK
  Applying PyApp.0008_auto_20170315_0752... OK
  Applying PyApp.0009_auto_20170315_0753... OK
  Applying PyApp.0010_auto_20170315_0806... OK
  Applying PyApp.0011_auto_20170315_0814... OK
  Applying PyApp.0012_auto_20170315_0820... OK
  Applying PyApp.0013_auto_20170315_0822... OK
  Applying PyApp.0014_auto_20170315_0907... OK
  Applying PyApp.0015_auto_20170315_1041... OK
  Applying PyApp.0016_auto_20170315_1355... OK
  Applying PyApp.0017_auto_20170315_1401... OK
  Applying PyApp.0018_auto_20170331_1348... OK
  Applying PyApp.0019_auto_20170331_1349... OK
  Applying PyApp.0020_auto_20170331_1350... OK
  Applying PyApp.0021_auto_20170331_1458... OK
  Applying PyApp.0022_delete_postoffice... OK
  Applying PyApp.0023_posoffice... OK
  Applying PyApp.0024_auto_20170331_1504... OK
  Applying PyApp.0025_auto_20170331_1511... OK
  Applying contenttypes.0001_initial... OK
  Applying auth.0001_initial... OK
  Applying admin.0001_initial... OK
  Applying contenttypes.0002_remove_content_type_name... OK
  Applying auth.0002_alter_permission_name_max_length... OK
  Applying auth.0003_alter_user_email_max_length... OK
  Applying auth.0004_alter_user_username_opts... OK
  Applying auth.0005_alter_user_last_login_null... OK
  Applying auth.0006_require_contenttypes_0002... OK
  Applying sessions.0001_initial... OK
(vir_env) admins-MacBook-Pro-3:src admin$ 

Android DialogFragment vs Dialog

DialogFragment is basically a Fragment that can be used as a dialog.

Using DialogFragment over Dialog due to the following reasons:

  • DialogFragment is automatically re-created after configuration changes and save & restore flow
  • DialogFragment inherits full Fragment’s lifecycle
  • No more IllegalStateExceptions and leaked window crashes. This was pretty common when the activity was destroyed with the Alert Dialog still there.

More detail

How to preventDefault on anchor tags?

An alternative might be:

<span ng-click="do()">Click</span>

Is there a way to avoid null check before the for-each loop iteration starts?

If possible, you should design your code such that the collections aren't null in the first place.

null collections are bad practice (for this reason); you should use empty collections instead. (eg, Collections.emptyList())

Alternatively, you could make a wrapper class that implements Iterable and takes a collections, and handles a null collection.
You could then write foreach(T obj : new Nullable<T>(list1))

How to download Javadoc to read offline?

The updated latest version of "The Java language Specification" can be found via the following links. Java 7

Java 8

Convert UTC date time to local date time

I've created one function which converts all the timezones into local time.

I did not used getTimezoneOffset(), because it does not returns proper offset value

Requirements:

1. npm i moment-timezone

function utcToLocal(utcdateTime, tz) {
    var zone = moment.tz(tz).format("Z") // Actual zone value e:g +5:30
    var zoneValue = zone.replace(/[^0-9: ]/g, "") // Zone value without + - chars
    var operator = zone && zone.split("") && zone.split("")[0] === "-" ? "-" : "+" // operator for addition subtraction
    var localDateTime
    var hours = zoneValue.split(":")[0]
    var minutes = zoneValue.split(":")[1]
    if (operator === "-") {
        localDateTime = moment(utcdateTime).subtract(hours, "hours").subtract(minutes, "minutes").format("YYYY-MM-DD HH:mm:ss")
    } else if (operator) {
        localDateTime = moment(utcdateTime).add(hours, "hours").add(minutes, "minutes").format("YYYY-MM-DD HH:mm:ss")
    } else {
        localDateTime = "Invalid Timezone Operator"
    }
    return localDateTime
}

utcToLocal("2019-11-14 07:15:37", "Asia/Kolkata")

//Returns "2019-11-14 12:45:37"

How to make 'submit' button disabled?

Form validation is very much straight forward in Angular 2

Here is an example,

<form (ngSubmit)="onSubmit()" #myForm="ngForm">

 <div class="form-group">
  <label for="firstname">First Name</label>
  <input type="text" class="form-control" id="firstname" 
   required [(ngModel)]="firstname" name="firstname">
 </div>

 <div class="form-group">
  <label for="middlename">Middle Name</label>
  <input type="text"  class="form-control" id="middlename" 
   [(ngModel)]="middlename" name="middlename">
 </div>

 <div class="form-group">
  <label for="lastname">Last Name</label>
  <input type="text"  class="form-control" id="lastname" 
   required minlength = '2' maxlength="6" [(ngModel)] = "lastname" name="lastname">
 </div>

 <div class="form-group">
  <label for="mobnumber">Mob Number</label>
  <input type="text"  class="form-control" id="mobnumber"  
   minlength = '2' maxlength="10" pattern="^[0-9()\-+\s]+$" 
   [(ngModel)] = "mobnumber" name="mobnumber">
 </div>

 <button type="submit" [disabled]="!myForm.form.valid">Submit</button>

</form>

Check this plunker for demo

More info

Split string into string array of single characters

You can just use String.ToCharArray() and then treat each char as a string in your code.

Here's an example:

    foreach (char c in s.ToCharArray())
        Debug.Log("one character ... " +c);

Pass data from Activity to Service using an Intent

Service: startservice can cause side affects,best way to use messenger and pass data.

private CallBackHandler mServiceHandler= new CallBackHandler(this);
private Messenger mServiceMessenger=null;
//flag with which the activity sends the data to service
private static final int DO_SOMETHING=1;

private static class CallBackHandler extends android.os.Handler {

private final WeakReference<Service> mService;

public CallBackHandler(Service service) {
    mService= new WeakReference<Service>(service);
}

public void handleMessage(Message msg) {
    //Log.d("CallBackHandler","Msg::"+msg);
    if(DO_SOMETHING==msg.arg1)
    mSoftKeyService.get().dosomthing()
}
}

Activity:Get Messenger from Intent fill it pass data and pass the message back to service

private Messenger mServiceMessenger;
@Override
protected void onCreate(Bundle savedInstanceState) {
mServiceMessenger = (Messenger)extras.getParcelable("myHandler");
}


private void sendDatatoService(String data){
Intent serviceIntent= new 
Intent(BaseActivity.this,Service.class);
Message msg = Message.obtain();
msg.obj =data;
msg.arg1=Service.DO_SOMETHING;
mServiceMessenger.send(msg);
}

What's the difference between "Write-Host", "Write-Output", or "[console]::WriteLine"?

Write-Output should be used when you want to send data on in the pipe line, but not necessarily want to display it on screen. The pipeline will eventually write it to out-default if nothing else uses it first.

Write-Host should be used when you want to do the opposite.

[console]::WriteLine is essentially what Write-Host is doing behind the scenes.

Run this demonstration code and examine the result.

function Test-Output {
    Write-Output "Hello World"
}

function Test-Output2 {
    Write-Host "Hello World" -foreground Green
}

function Receive-Output {
    process { Write-Host $_ -foreground Yellow }
}

#Output piped to another function, not displayed in first.
Test-Output | Receive-Output

#Output not piped to 2nd function, only displayed in first.
Test-Output2 | Receive-Output 

#Pipeline sends to Out-Default at the end.
Test-Output 

You'll need to enclose the concatenation operation in parentheses, so that PowerShell processes the concatenation before tokenizing the parameter list for Write-Host, or use string interpolation

write-host ("count=" + $count)
# or
write-host "count=$count"

BTW - Watch this video of Jeffrey Snover explaining how the pipeline works. Back when I started learning PowerShell I found this to be the most useful explanation of how the pipeline works.

How to copy a file to a remote server in Python using SCP or SSH?

There are a couple of different ways to approach the problem:

  1. Wrap command-line programs
  2. use a Python library that provides SSH capabilities (eg - Paramiko or Twisted Conch)

Each approach has its own quirks. You will need to setup SSH keys to enable password-less logins if you are wrapping system commands like "ssh", "scp" or "rsync." You can embed a password in a script using Paramiko or some other library, but you might find the lack of documentation frustrating, especially if you are not familiar with the basics of the SSH connection (eg - key exchanges, agents, etc). It probably goes without saying that SSH keys are almost always a better idea than passwords for this sort of stuff.

NOTE: its hard to beat rsync if you plan on transferring files via SSH, especially if the alternative is plain old scp.

I've used Paramiko with an eye towards replacing system calls but found myself drawn back to the wrapped commands due to their ease of use and immediate familiarity. You might be different. I gave Conch the once-over some time ago but it didn't appeal to me.

If opting for the system-call path, Python offers an array of options such as os.system or the commands/subprocess modules. I'd go with the subprocess module if using version 2.4+.

How to get value of a div using javascript

First of all

<div id="demo" align="center"  value="1"></div>

that is not valid HTML. Read up on custom data attributes or use the following instead:

<div id="demo" align="center" data-value="1"></div>

Since "data-value" is an attribute, you have to use the getAttribute function to retrieve its value.

var cookieValue = document.getElementById("demo").getAttribute("data-value"); 

Delete all rows in table

You can rename the table in question, create a table with an identical schema, and then drop the original table at your leisure.

See the MySQL 5.1 Reference Manual for the [RENAME TABLE][1] and [CREATE TABLE][2] commands.

RENAME TABLE tbl TO tbl_old;

CREATE TABLE tbl LIKE tbl_old;

DROP TABLE tbl_old; -- at your leisure

This approach can help minimize application downtime.

Change Git repository directory location.

While the question involves Git for Windows, this seems to be the top result even when searching for Visual Studio Tools For Git (extension in VS 2012, native support in VS 2013).

Using the solutions above as a guide I determined that Visual Studio Git Tools makes moving repos (or even entire directory structure for all repos) locally very easy.

1) Close Visual Studio. 2) Move the Repo folder(s) to new location. 3) Open Visual Studio. Open Team Explorer. Switch to "Connect" view (plug icon at top). 3a) If Repos still show old path, click Refresh to force an update. 4) Repos that were moved locally should no longer be showing in "Local Git Repositories". 5) Click Add (not new or clone) and select the repo folder to add.

In step 5 you really are just providing a search path and the search automatically includes all subfolders. If you have multiple repos organized under a single root (independent repos just having the same parent folder) then selecting the parent will include all repos found below that.

Example: E:\Repos\RepoA E:\Repos\RepoB E:\Repos\RepoC

In Visual Studio Team Explorer [Add] > "E:\Repos\" > [Add] will return all three to the Local Repositories.

Javascript document.getElementById("id").value returning null instead of empty string when the element is an empty text box

Posting your HTML might help a bit. Instead, you can get the element first and then check if it is null or not and then ask for its value rather than just asking for the value directly without knowing if the element is visible on the HTML or not.

element1 = document.getElementById(id);

if(element1 != null)
{
    //code to set the value variable.
}

How to run .sql file in Oracle SQL developer tool to import database?

You need to Open the SQL Developer first and then click on File option and browse to the location where your .sql is placed. Once you are at the location where file is placed double click on it, this will get the file open in SQL Developer. Now select all of the content of file (CTRL + A) and press F9 key. Just make sure there is a commit statement at the end of the .sql script so that the changes are persisted in the database

conflicting types error when compiling c program using gcc

To answer a more generic case, this error is noticed when you pick a function name which is already used in some built in library. For e.g., select.

A simple method to know about it is while compiling the file, the compiler will indicate the previous declaration.

Send data through routing paths in Angular

In navigateExtra we can pass only some specific name as argument otherwise it showing error like below: For Ex- Here I want to pass customer key in router navigate and I pass like this-

this.Router.navigate(['componentname'],{cuskey: {customerkey:response.key}});

but it showing some error like below:

Argument of type '{ cuskey: { customerkey: any; }; }' is not assignable to parameter of type 'NavigationExtras'.
  Object literal may only specify known properties, and 'cuskey' does not exist in type 'NavigationExt## Heading ##ras'

.

Solution: we have to write like this:

this.Router.navigate(['componentname'],{state: {customerkey:response.key}});

Dialog with transparent background in Android

Same solution as zGnep but using xml:

android:background="@null"

How to create custom spinner like border around the spinner with down triangle on the right side?

There are two ways to achieve this.

1- As already proposed u can set the background of your spinner as custom 9 patch Image with all the adjustments made into it .

android:background="@drawable/btn_dropdown" 
android:clickable="true"
android:dropDownVerticalOffset="-10dip"
android:dropDownHorizontalOffset="0dip"
android:gravity="center"

If you want your Spinner to show With various different background colors i would recommend making the drop down image transparent, & loading that spinner in a relative layout with your color set in.

btn _dropdown is as:

<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item
    android:state_window_focused="false" android:state_enabled="true"
    android:drawable="@drawable/spinner_default" />
<item
    android:state_window_focused="false" android:state_enabled="false"
    android:drawable="@drawable/spinner_default" />
<item
    android:state_pressed="true"
    android:drawable="@drawable/spinner_pressed" />
<item
    android:state_focused="true" android:state_enabled="true"
    android:drawable="@drawable/spinner_pressed" />
<item
    android:state_enabled="true"
    android:drawable="@drawable/spinner_default" />
<item
    android:state_focused="true"
    android:drawable="@drawable/spinner_pressed" />
<item
    android:drawable="@drawable/spinner_default" />
</selector>

where the various states of pngwould define your various States of spinner seleti

querySelectorAll with multiple conditions

With pure JavaScript you can do this (such as SQL) and anything you need, basically:

_x000D_
_x000D_
<html>_x000D_
_x000D_
<body>_x000D_
_x000D_
<input type='button' value='F3' class="c2" id="btn_1">_x000D_
<input type='button' value='F3' class="c3" id="btn_2">_x000D_
<input type='button' value='F1' class="c2" id="btn_3">_x000D_
_x000D_
<input type='submit' value='F2' class="c1" id="btn_4">_x000D_
<input type='submit' value='F1' class="c3" id="btn_5">_x000D_
<input type='submit' value='F2' class="c1" id="btn_6">_x000D_
_x000D_
<br/>_x000D_
<br/>_x000D_
_x000D_
<button onclick="myFunction()">Try it</button>_x000D_
_x000D_
<script>_x000D_
    function myFunction() _x000D_
    {_x000D_
        var arrFiltered = document.querySelectorAll('input[value=F2][type=submit][class=c1]');_x000D_
_x000D_
            arrFiltered.forEach(function (el)_x000D_
            {                _x000D_
                var node = document.createElement("p");_x000D_
                _x000D_
                node.innerHTML = el.getAttribute('id');_x000D_
_x000D_
                window.document.body.appendChild(node);_x000D_
            });_x000D_
        }_x000D_
    </script>_x000D_
_x000D_
</body>_x000D_
_x000D_
</html>
_x000D_
_x000D_
_x000D_

How to open every file in a folder

The code below reads for any text files available in the directory which contains the script we are running. Then it opens every text file and stores the words of the text line into a list. After store the words we print each word line by line

import os, fnmatch

listOfFiles = os.listdir('.')
pattern = "*.txt"
store = []
for entry in listOfFiles:
    if fnmatch.fnmatch(entry, pattern):
        _fileName = open(entry,"r")
        if _fileName.mode == "r":
            content = _fileName.read()
            contentList = content.split(" ")
            for i in contentList:
                if i != '\n' and i != "\r\n":
                    store.append(i)

for i in store:
    print(i)

List<T> OrderBy Alphabetical Order

If you mean an in-place sort (i.e. the list is updated):

people.Sort((x, y) => string.Compare(x.LastName, y.LastName));

If you mean a new list:

var newList = people.OrderBy(x=>x.LastName).ToList(); // ToList optional

How to disable a button when an input is empty?

Using constants allows to combine multiple fields for verification:

_x000D_
_x000D_
class LoginFrm extends React.Component {_x000D_
  constructor() {_x000D_
    super();_x000D_
    this.state = {_x000D_
      email: '',_x000D_
      password: '',_x000D_
    };_x000D_
  }_x000D_
  _x000D_
  handleEmailChange = (evt) => {_x000D_
    this.setState({ email: evt.target.value });_x000D_
  }_x000D_
  _x000D_
  handlePasswordChange = (evt) => {_x000D_
    this.setState({ password: evt.target.value });_x000D_
  }_x000D_
  _x000D_
  handleSubmit = () => {_x000D_
    const { email, password } = this.state;_x000D_
    alert(`Welcome ${email} password: ${password}`);_x000D_
  }_x000D_
  _x000D_
  render() {_x000D_
    const { email, password } = this.state;_x000D_
    const enabled =_x000D_
          email.length > 0 &&_x000D_
          password.length > 0;_x000D_
    return (_x000D_
      <form onSubmit={this.handleSubmit}>_x000D_
        <input_x000D_
          type="text"_x000D_
          placeholder="Email"_x000D_
          value={this.state.email}_x000D_
          onChange={this.handleEmailChange}_x000D_
        />_x000D_
        _x000D_
        <input_x000D_
          type="password"_x000D_
          placeholder="Password"_x000D_
          value={this.state.password}_x000D_
          onChange={this.handlePasswordChange}_x000D_
        />_x000D_
        <button disabled={!enabled}>Login</button>_x000D_
      </form>_x000D_
    )_x000D_
  }_x000D_
}_x000D_
_x000D_
ReactDOM.render(<LoginFrm />, document.body);
_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>_x000D_
<body>_x000D_
_x000D_
_x000D_
</body>
_x000D_
_x000D_
_x000D_

how to sort an ArrayList in ascending order using Collections and Comparator

Just throwing this out there...Can't you just do:

Collections.sort(myarrayList);

It's been awhile though...

TypeError: expected a character buffer object - while trying to save integer to textfile

from __future__ import with_statement
with open('file.txt','r+') as f:
    counter = str(int(f.read().strip())+1)
    f.seek(0)
    f.write(counter)

Is an entity body allowed for an HTTP DELETE request?

Using DELETE with a Body is risky... I prefer this approach for List Operations over REST:

Regular Operations

GET /objects/ Gets all Objects

GET /object/ID Gets an Object with specified ID

POST /objects Adds a new Object

PUT /object/ID Adds an Object with specified ID, Updates an Object

DELETE /object/ID Deletes the object with specified ID

All Custom actions are POST

POST /objects/addList Adds a List or Array of Objects included in body

POST /objects/deleteList Deletes a List of Objects included in body

POST /objects/customQuery Creates a List based on custom query in body

If a client doesn't support your extended operations they can work in the regular way.

Browse and display files in a git repo without cloning

Git is distributed version control system, while Subversion is centralized (client-server) version control system. They work differently; get used to that. Please read my answer explaining the consequences of that difference to git equivalent of svn status -u question at StackOverflow.

Repeating myself a bit: in centralized version control system (like CVS or Subversion) almost all commands are processed on server, and involve network. Very few commands are performed locally. Note that to have good performance of "svn status" and "svn diff" Subversion stores 'pristine copy' of checked-out version on client, to not have to involve network transfer for those common operations (this means that Subversion checkout = 2 x size of working directory at least).

In distributed version control system (like Git, Mercurial or Bazaar), where you have local copy (clone) of a whole repository, almost all commands are performed on client. Very few commands require network connection to other repository (to server).

The number of command you can perform on server is limited.

  • You can list all references on remote with "git ls-remote <URL>".
  • You can get snapshot of (part) of repository (if remote server enabled it) with
    "git archive --remote=<URL> HEAD".
  • You can clone only a few last commits (so called "shallow clone") with
    "git clone --depth=1 <URL>".
  • If server provides git web interface to repository, you can use it to browse.

Cannot connect to MySQL Workbench on mac. Can't connect to MySQL server on '127.0.0.1' (61) Mac Macintosh

brew services start mysql defualt set --bind-address=127.0.0.1 with /usr/local/Cellar/mysql/5.6.27/homebrew.mxcl.mysql.plist,so replace --bind-address=127.0.0.1 with --bind-address=* or --bind-address=0.0.0.0

How do you get the file size in C#?

The FileInfo class' Length property returns the size of the file (not the size on disk). If you want a formatted file size (i.e. 15 KB) rather than a long byte value you can use CSharpLib, a package I've made that adds more functionality to the FileInfo class. Here's an example:

using CSharpLib;
FileInfo info = new FileInfo("sample.txt");
Console.WriteLine(info.FormatBytes());  // Output: 15 MB

How to access parent scope from within a custom directive *with own scope* in AngularJS?

Here's a trick I used once: create a "dummy" directive to hold the parent scope and place it somewhere outside the desired directive. Something like:

module.directive('myDirectiveContainer', function () {
    return {
        controller: function ($scope) {
            this.scope = $scope;
        }
    };
});

module.directive('myDirective', function () {
    return {
        require: '^myDirectiveContainer',
        link: function (scope, element, attrs, containerController) {
            // use containerController.scope here...
        }
    };
});

and then

<div my-directive-container="">
    <div my-directive="">
    </div>
</div>

Maybe not the most graceful solution, but it got the job done.

Select records from NOW() -1 Day

Be aware that the result may be slightly different than you expect.

NOW() returns a DATETIME.

And INTERVAL works as named, e.g. INTERVAL 1 DAY = 24 hours.

So if your script is cron'd to run at 03:00, it will miss the first three hours of records from the 'oldest' day.

To get the whole day use CURDATE() - INTERVAL 1 DAY. This will get back to the beginning of the previous day regardless of when the script is run.

C# "internal" access modifier when doing unit testing

If you want to test private methods, have a look at PrivateObject and PrivateType in the Microsoft.VisualStudio.TestTools.UnitTesting namespace. They offer easy to use wrappers around the necessary reflection code.

Docs: PrivateType, PrivateObject

For VS2017 & 2019, you can find these by downloading the MSTest.TestFramework nuget

How do I add a .click() event to an image?

First of all, this line

<img src="http://soulsnatcher.bplaced.net/LDRYh.jpg" alt="unfinished bingo card" />.click()

You're mixing HTML and JavaScript. It doesn't work like that. Get rid of the .click() there.

If you read the JavaScript you've got there, document.getElementById('foo') it's looking for an HTML element with an ID of foo. You don't have one. Give your image that ID:

<img id="foo" src="http://soulsnatcher.bplaced.net/LDRYh.jpg" alt="unfinished bingo card" />

Alternatively, you could throw the JS in a function and put an onclick in your HTML:

<img src="http://soulsnatcher.bplaced.net/LDRYh.jpg" alt="unfinished bingo card" onclick="myfunction()" />

I suggest you do some reading up on JavaScript and HTML though.


The others are right about needing to move the <img> above the JS click binding too.

How do I automatically set the $DISPLAY variable for my current session?

Here's something I've just knocked up. It inspects the environment of the last-launched "gnome-session" process (DISPLAY is set correctly when VNC launches a session/window manager). Replace "gnome-session" with the name of whatever process your VNC server launches on startup.

PID=`pgrep -n -u $USER gnome-session`
if [ -n "$PID" ]; then
    export DISPLAY=`awk 'BEGIN{FS="="; RS="\0"}  $1=="DISPLAY" {print $2; exit}' /proc/$PID/environ`
    echo "DISPLAY set to $DISPLAY"
else
    echo "Could not set DISPLAY"
fi
unset PID

You should just be able to drop that in your .bashrc file.

Change the background color of CardView programmatically

In JAVA

cardView.setCardBackgroundColor(0xFFFEFEFE);

android use ARGB colors. you can use like this (0xFF + RGB COLOR)--Hard-coded color.

Fast Bitmap Blur For Android SDK

For those still having issues with Renderscript support library on x86 chipsets, please have a look at this post by the creator of the library. It looks like the fix he prepared didn't make it somehow to the Build Tools v20.0.0, so he provides the files to fix it manually and a brief explanation of how to do it.

https://code.google.com/p/android/issues/detail?can=2&start=0&num=100&q=&colspec=ID%20Type%20Status%20Owner%20Summary%20Stars&groupby=&sort=&id=71347

Groovy Shell warning "Could not open/create prefs root node ..."

If anyone is trying to solve this on a 64-bit version of Windows, you might need to create the following key:

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\JavaSoft\Prefs

How to open Visual Studio Code from the command line on OSX?

I have a ~/bin/code shell script that matches the command @BengaminPasero wrote.

#!/bin/bash
VSCODE_CWD="$PWD" open -n -b "com.microsoft.VSCode" --args $*

I prefix ~/bin: to my $PATH which allows me to add a bunch of one off scripts without polluting my ~/.bash_profile script.

Storing query results into a variable and modifying it inside a Stored Procedure

Yup, this is possible of course. Here are several examples.

-- one way to do this
DECLARE @Cnt int

SELECT @Cnt = COUNT(SomeColumn)
FROM TableName
GROUP BY SomeColumn

-- another way to do the same thing
DECLARE @StreetName nvarchar(100)
SET @StreetName = (SELECT Street_Name from Streets where Street_ID = 123)

-- Assign values to several variables at once
DECLARE @val1 nvarchar(20)
DECLARE @val2 int
DECLARE @val3 datetime
DECLARE @val4 uniqueidentifier
DECLARE @val5 double

SELECT @val1 = TextColumn,
@val2 = IntColumn,
@val3 = DateColumn,
@val4 = GuidColumn,
@val5 = DoubleColumn
FROM SomeTable

How to remove last n characters from a string in Bash?

You could use sed,

sed 's/.\{4\}$//' <<< "$var"

EXample:

$ var="some string.rtf"
$ var1=$(sed 's/.\{4\}$//' <<< "$var")
$ echo $var1
some string

Is there any simple way to convert .xls file to .csv file? (Excel)

I integrate the @mattmc3 aswer. If you want to convert a xlsx file you should use this connection string (the string provided by matt works for xls formats, not xlsx):

var cnnStr = String.Format("Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties=\"Excel 12.0;IMEX=1;HDR=NO\"", excelFilePath);

Count how many files in directory PHP

I use this:

count(glob("yourdir/*",GLOB_BRACE))

Reference alias (calculated in SELECT) in WHERE clause

It's actually possible to effectively define a variable that can be used in both the SELECT, WHERE and other clauses.

A cross join doesn't necessarily allow for appropriate binding to the referenced table columns, however OUTER APPLY does - and treats nulls more transparently.

SELECT
    vars.BalanceDue
FROM
    Entity e
OUTER APPLY (
    SELECT
        -- variables   
        BalanceDue = e.EntityTypeId,
        Variable2 = ...some..long..complex..expression..etc...
    ) vars
WHERE
    vars.BalanceDue > 0

Kudos to Syed Mehroz Alam.

How do I change the title of the "back" button on a Navigation Bar

This should be placed in the method that calls the ViewController titled "NewTitle". Right before the push or popViewController statement.

UIBarButtonItem *newBackButton = 
        [[UIBarButtonItem alloc] initWithTitle:@"NewTitle" 
                                         style:UIBarButtonItemStyleBordered 
                                        target:nil 
                                        action:nil];
[[self navigationItem] setBackBarButtonItem:newBackButton];
[newBackButton release];

Unable to instantiate default tuplizer [org.hibernate.tuple.entity.PojoEntityTuplizer]

I am using spring 3.0 and Hibernate 3.6 in my project. I ran into the same error just now. Googling this error message brought me to this page.

Funtik's comment on Jan 17 '12 at 8:49 helped me resolve the issue-

"This tells me that javassist cannot be accessed. How do you include this library into the project?"

So, I included java assist in my maven pom file as below:

<dependency>
    <groupId>javassist</groupId>
    <artifactId>javassist</artifactId>
    <version>3.12.1.GA</version>
</dependency>

This resolved the issue for me. Thanks Funtik.

Correct way to write line to file?

The python docs recommend this way:

with open('file_to_write', 'w') as f:
    f.write('file contents\n')

So this is the way I usually do it :)

Statement from docs.python.org:

It is good practice to use the 'with' keyword when dealing with file objects. This has the advantage that the file is properly closed after its suite finishes, even if an exception is raised on the way. It is also much shorter than writing equivalent try-finally blocks.

startForeground fail after upgrade to Android 8.1

In my case, it's because we tried to post a notification without specifying the NotificationChannel:

public static final String NOTIFICATION_CHANNEL_ID_SERVICE = "com.mypackage.service";
public static final String NOTIFICATION_CHANNEL_ID_TASK = "com.mypackage.download_info";

public void initChannel(){
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        NotificationManager nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        nm.createNotificationChannel(new NotificationChannel(NOTIFICATION_CHANNEL_ID_SERVICE, "App Service", NotificationManager.IMPORTANCE_DEFAULT));
        nm.createNotificationChannel(new NotificationChannel(NOTIFICATION_CHANNEL_ID_INFO, "Download Info", NotificationManager.IMPORTANCE_DEFAULT));
    }
}

The best place to put above code is in onCreate() method in the Application class, so that we just need to declare it once for all:

public class App extends Application {

    @Override
    public void onCreate() {
        super.onCreate();
        initChannel();
    }
}

After we set this up, we can use notification with the channelId we just specified:

Intent i = new Intent(this, MainActivity.class);
i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);
PendingIntent pi = PendingIntent.getActivity(this, 0, i, PendingIntent.FLAG_UPDATE_CURRENT);
NotificationCompat.Builder builder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID_INFO);
            .setContentIntent(pi)
            .setWhen(System.currentTimeMillis())
            .setContentTitle("VirtualBox.exe")
            .setContentText("Download completed")
            .setSmallIcon(R.mipmap.ic_launcher);

Then, we can use it to post a notification:

int notifId = 45;
NotificationManager nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
nm.notify(notifId, builder.build());

If you want to use it as foreground service's notification:

startForeground(notifId, builder.build());

display HTML page after loading complete

put an overlay on the page

#loading-mask {
    background-color: white;
    height: 100%;
    left: 0;
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 9999;
}

and then delete that element in a window.onload handler or, hide it

window.onload=function() {
    document.getElementById('loading-mask').style.display='none';
}

Of course you should use your javascript library (jquery,prototype..) specific onload handler if you are using a library.

Closing database connections in Java

When you are done with using your Connection, you need to explicitly close it by calling its close() method in order to release any other database resources (cursors, handles, etc.) the connection may be holding on to.

Actually, the safe pattern in Java is to close your ResultSet, Statement, and Connection (in that order) in a finally block when you are done with them. Something like this:

Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;

try {
    // Do stuff
    ...

} catch (SQLException ex) {
    // Exception handling stuff
    ...
} finally {
    if (rs != null) {
        try {
            rs.close();
        } catch (SQLException e) { /* Ignored */}
    }
    if (ps != null) {
        try {
            ps.close();
        } catch (SQLException e) { /* Ignored */}
    }
    if (conn != null) {
        try {
            conn.close();
        } catch (SQLException e) { /* Ignored */}
    }
}

The finally block can be slightly improved into (to avoid the null check):

} finally {
    try { rs.close(); } catch (Exception e) { /* Ignored */ }
    try { ps.close(); } catch (Exception e) { /* Ignored */ }
    try { conn.close(); } catch (Exception e) { /* Ignored */ }
}

But, still, this is extremely verbose so you generally end up using an helper class to close the objects in null-safe helper methods and the finally block becomes something like this:

} finally {
    DbUtils.closeQuietly(rs);
    DbUtils.closeQuietly(ps);
    DbUtils.closeQuietly(conn);
}

And, actually, the Apache Commons DbUtils has a DbUtils class which is precisely doing that, so there isn't any need to write your own.

Converting string to tuple without splitting characters

You can use eval()

>>> a = ['Quattro TT']  
>>> eval(str(a))
['Quattro TT']

Keep overflow div scrolled to bottom unless user scrolls up

$('#yourDivID').animate({ scrollTop: $(document).height() }, "slow");
return false;

This will calculate the ScrollTop Position from the height of #yourDivID using the $(document).height() property so that even if dynamic contents are added to the div the scroller will always be at the bottom position. Hope this helps. But it also has a small bug even if we scroll up and leaves the mouse pointer from the scroller it will automatically come to the bottom position. If somebody could correct that also it will be nice.

How to make CSS width to fill parent?

box-sizing: border-box;
width: 100%;
padding: 5px;

box-sizing: border box; makes it so that padding, margin and border are included in the width calculations.

MDN

What are Aggregates and PODs and how/why are they special?

How to read:

This article is rather long. If you want to know about both aggregates and PODs (Plain Old Data) take time and read it. If you are interested just in aggregates, read only the first part. If you are interested only in PODs then you must first read the definition, implications, and examples of aggregates and then you may jump to PODs but I would still recommend reading the first part in its entirety. The notion of aggregates is essential for defining PODs. If you find any errors (even minor, including grammar, stylistics, formatting, syntax, etc.) please leave a comment, I'll edit.

This answer applies to C++03. For other C++ standards see:

What are aggregates and why they are special

Formal definition from the C++ standard (C++03 8.5.1 §1):

An aggregate is an array or a class (clause 9) with no user-declared constructors (12.1), no private or protected non-static data members (clause 11), no base classes (clause 10), and no virtual functions (10.3).

So, OK, let's parse this definition. First of all, any array is an aggregate. A class can also be an aggregate if… wait! nothing is said about structs or unions, can't they be aggregates? Yes, they can. In C++, the term class refers to all classes, structs, and unions. So, a class (or struct, or union) is an aggregate if and only if it satisfies the criteria from the above definitions. What do these criteria imply?

  • This does not mean an aggregate class cannot have constructors, in fact it can have a default constructor and/or a copy constructor as long as they are implicitly declared by the compiler, and not explicitly by the user

  • No private or protected non-static data members. You can have as many private and protected member functions (but not constructors) as well as as many private or protected static data members and member functions as you like and not violate the rules for aggregate classes

  • An aggregate class can have a user-declared/user-defined copy-assignment operator and/or destructor

  • An array is an aggregate even if it is an array of non-aggregate class type.

Now let's look at some examples:

class NotAggregate1
{
  virtual void f() {} //remember? no virtual functions
};

class NotAggregate2
{
  int x; //x is private by default and non-static 
};

class NotAggregate3
{
public:
  NotAggregate3(int) {} //oops, user-defined constructor
};

class Aggregate1
{
public:
  NotAggregate1 member1;   //ok, public member
  Aggregate1& operator=(Aggregate1 const & rhs) {/* */} //ok, copy-assignment  
private:
  void f() {} // ok, just a private function
};

You get the idea. Now let's see how aggregates are special. They, unlike non-aggregate classes, can be initialized with curly braces {}. This initialization syntax is commonly known for arrays, and we just learnt that these are aggregates. So, let's start with them.

Type array_name[n] = {a1, a2, …, am};

if(m == n)
the ith element of the array is initialized with ai
else if(m < n)
the first m elements of the array are initialized with a1, a2, …, am and the other n - m elements are, if possible, value-initialized (see below for the explanation of the term)
else if(m > n)
the compiler will issue an error
else (this is the case when n isn't specified at all like int a[] = {1, 2, 3};)
the size of the array (n) is assumed to be equal to m, so int a[] = {1, 2, 3}; is equivalent to int a[3] = {1, 2, 3};

When an object of scalar type (bool, int, char, double, pointers, etc.) is value-initialized it means it is initialized with 0 for that type (false for bool, 0.0 for double, etc.). When an object of class type with a user-declared default constructor is value-initialized its default constructor is called. If the default constructor is implicitly defined then all nonstatic members are recursively value-initialized. This definition is imprecise and a bit incorrect but it should give you the basic idea. A reference cannot be value-initialized. Value-initialization for a non-aggregate class can fail if, for example, the class has no appropriate default constructor.

Examples of array initialization:

class A
{
public:
  A(int) {} //no default constructor
};
class B
{
public:
  B() {} //default constructor available
};
int main()
{
  A a1[3] = {A(2), A(1), A(14)}; //OK n == m
  A a2[3] = {A(2)}; //ERROR A has no default constructor. Unable to value-initialize a2[1] and a2[2]
  B b1[3] = {B()}; //OK b1[1] and b1[2] are value initialized, in this case with the default-ctor
  int Array1[1000] = {0}; //All elements are initialized with 0;
  int Array2[1000] = {1}; //Attention: only the first element is 1, the rest are 0;
  bool Array3[1000] = {}; //the braces can be empty too. All elements initialized with false
  int Array4[1000]; //no initializer. This is different from an empty {} initializer in that
  //the elements in this case are not value-initialized, but have indeterminate values 
  //(unless, of course, Array4 is a global array)
  int array[2] = {1, 2, 3, 4}; //ERROR, too many initializers
}

Now let's see how aggregate classes can be initialized with braces. Pretty much the same way. Instead of the array elements we will initialize the non-static data members in the order of their appearance in the class definition (they are all public by definition). If there are fewer initializers than members, the rest are value-initialized. If it is impossible to value-initialize one of the members which were not explicitly initialized, we get a compile-time error. If there are more initializers than necessary, we get a compile-time error as well.

struct X
{
  int i1;
  int i2;
};
struct Y
{
  char c;
  X x;
  int i[2];
  float f; 
protected:
  static double d;
private:
  void g(){}      
}; 

Y y = {'a', {10, 20}, {20, 30}};

In the above example y.c is initialized with 'a', y.x.i1 with 10, y.x.i2 with 20, y.i[0] with 20, y.i[1] with 30 and y.f is value-initialized, that is, initialized with 0.0. The protected static member d is not initialized at all, because it is static.

Aggregate unions are different in that you may initialize only their first member with braces. I think that if you are advanced enough in C++ to even consider using unions (their use may be very dangerous and must be thought of carefully), you could look up the rules for unions in the standard yourself :).

Now that we know what's special about aggregates, let's try to understand the restrictions on classes; that is, why they are there. We should understand that memberwise initialization with braces implies that the class is nothing more than the sum of its members. If a user-defined constructor is present, it means that the user needs to do some extra work to initialize the members therefore brace initialization would be incorrect. If virtual functions are present, it means that the objects of this class have (on most implementations) a pointer to the so-called vtable of the class, which is set in the constructor, so brace-initialization would be insufficient. You could figure out the rest of the restrictions in a similar manner as an exercise :).

So enough about the aggregates. Now we can define a stricter set of types, to wit, PODs

What are PODs and why they are special

Formal definition from the C++ standard (C++03 9 §4):

A POD-struct is an aggregate class that has no non-static data members of type non-POD-struct, non-POD-union (or array of such types) or reference, and has no user-defined copy assignment operator and no user-defined destructor. Similarly, a POD-union is an aggregate union that has no non-static data members of type non-POD-struct, non-POD-union (or array of such types) or reference, and has no user-defined copy assignment operator and no user-defined destructor. A POD class is a class that is either a POD-struct or a POD-union.

Wow, this one's tougher to parse, isn't it? :) Let's leave unions out (on the same grounds as above) and rephrase in a bit clearer way:

An aggregate class is called a POD if it has no user-defined copy-assignment operator and destructor and none of its nonstatic members is a non-POD class, array of non-POD, or a reference.

What does this definition imply? (Did I mention POD stands for Plain Old Data?)

  • All POD classes are aggregates, or, to put it the other way around, if a class is not an aggregate then it is sure not a POD
  • Classes, just like structs, can be PODs even though the standard term is POD-struct for both cases
  • Just like in the case of aggregates, it doesn't matter what static members the class has

Examples:

struct POD
{
  int x;
  char y;
  void f() {} //no harm if there's a function
  static std::vector<char> v; //static members do not matter
};

struct AggregateButNotPOD1
{
  int x;
  ~AggregateButNotPOD1() {} //user-defined destructor
};

struct AggregateButNotPOD2
{
  AggregateButNotPOD1 arrOfNonPod[3]; //array of non-POD class
};

POD-classes, POD-unions, scalar types, and arrays of such types are collectively called POD-types.
PODs are special in many ways. I'll provide just some examples.

  • POD-classes are the closest to C structs. Unlike them, PODs can have member functions and arbitrary static members, but neither of these two change the memory layout of the object. So if you want to write a more or less portable dynamic library that can be used from C and even .NET, you should try to make all your exported functions take and return only parameters of POD-types.

  • The lifetime of objects of non-POD class type begins when the constructor has finished and ends when the destructor has finished. For POD classes, the lifetime begins when storage for the object is occupied and finishes when that storage is released or reused.

  • For objects of POD types it is guaranteed by the standard that when you memcpy the contents of your object into an array of char or unsigned char, and then memcpy the contents back into your object, the object will hold its original value. Do note that there is no such guarantee for objects of non-POD types. Also, you can safely copy POD objects with memcpy. The following example assumes T is a POD-type:

    #define N sizeof(T)
    char buf[N];
    T obj; // obj initialized to its original value
    memcpy(buf, &obj, N); // between these two calls to memcpy,
    // obj might be modified
    memcpy(&obj, buf, N); // at this point, each subobject of obj of scalar type
    // holds its original value
    
  • goto statement. As you may know, it is illegal (the compiler should issue an error) to make a jump via goto from a point where some variable was not yet in scope to a point where it is already in scope. This restriction applies only if the variable is of non-POD type. In the following example f() is ill-formed whereas g() is well-formed. Note that Microsoft's compiler is too liberal with this rule—it just issues a warning in both cases.

    int f()
    {
      struct NonPOD {NonPOD() {}};
      goto label;
      NonPOD x;
    label:
      return 0;
    }
    
    int g()
    {
      struct POD {int i; char c;};
      goto label;
      POD x;
    label:
      return 0;
    }
    
  • It is guaranteed that there will be no padding in the beginning of a POD object. In other words, if a POD-class A's first member is of type T, you can safely reinterpret_cast from A* to T* and get the pointer to the first member and vice versa.

The list goes on and on…

Conclusion

It is important to understand what exactly a POD is because many language features, as you see, behave differently for them.

phantomjs not waiting for "full" page load

this is my solution its worked for me .

page.onConsoleMessage = function(msg, lineNum, sourceId) {

    if(msg=='hey lets take screenshot')
    {
        window.setInterval(function(){      
            try
            {               
                 var sta= page.evaluateJavaScript("function(){ return jQuery.active;}");                     
                 if(sta == 0)
                 {      
                    window.setTimeout(function(){
                        page.render('test.png');
                        clearInterval();
                        phantom.exit();
                    },1000);
                 }
            }
            catch(error)
            {
                console.log(error);
                phantom.exit(1);
            }
       },1000);
    }       
};


page.open(address, function (status) {      
    if (status !== "success") {
        console.log('Unable to load url');
        phantom.exit();
    } else { 
       page.setContent(page.content.replace('</body>','<script>window.onload = function(){console.log(\'hey lets take screenshot\');}</script></body>'), address);
    }
});

How to set HttpResponse timeout for Android in Java

In my example, two timeouts are set. The connection timeout throws java.net.SocketTimeoutException: Socket is not connected and the socket timeout java.net.SocketTimeoutException: The operation timed out.

HttpGet httpGet = new HttpGet(url);
HttpParams httpParameters = new BasicHttpParams();
// Set the timeout in milliseconds until a connection is established.
// The default value is zero, that means the timeout is not used. 
int timeoutConnection = 3000;
HttpConnectionParams.setConnectionTimeout(httpParameters, timeoutConnection);
// Set the default socket timeout (SO_TIMEOUT) 
// in milliseconds which is the timeout for waiting for data.
int timeoutSocket = 5000;
HttpConnectionParams.setSoTimeout(httpParameters, timeoutSocket);

DefaultHttpClient httpClient = new DefaultHttpClient(httpParameters);
HttpResponse response = httpClient.execute(httpGet);

If you want to set the Parameters of any existing HTTPClient (e.g. DefaultHttpClient or AndroidHttpClient) you can use the function setParams().

httpClient.setParams(httpParameters);

Extend a java class from one file in another java file

Java doesn't use includes the way C does. Instead java uses a concept called the classpath, a list of resources containing java classes. The JVM can access any class on the classpath by name so if you can extend classes and refer to types simply by declaring them. The closes thing to an include statement java has is 'import'. Since classes are broken up into namespaces like foo.bar.Baz, if you're in the qux package and you want to use the Baz class without having to use its full name of foo.bar.Baz, then you need to use an import statement at the beginning of your java file like so: import foo.bar.Baz

Is gcc's __attribute__((packed)) / #pragma pack unsafe?

Yes, __attribute__((packed)) is potentially unsafe on some systems. The symptom probably won't show up on an x86, which just makes the problem more insidious; testing on x86 systems won't reveal the problem. (On the x86, misaligned accesses are handled in hardware; if you dereference an int* pointer that points to an odd address, it will be a little slower than if it were properly aligned, but you'll get the correct result.)

On some other systems, such as SPARC, attempting to access a misaligned int object causes a bus error, crashing the program.

There have also been systems where a misaligned access quietly ignores the low-order bits of the address, causing it to access the wrong chunk of memory.

Consider the following program:

#include <stdio.h>
#include <stddef.h>
int main(void)
{
    struct foo {
        char c;
        int x;
    } __attribute__((packed));
    struct foo arr[2] = { { 'a', 10 }, {'b', 20 } };
    int *p0 = &arr[0].x;
    int *p1 = &arr[1].x;
    printf("sizeof(struct foo)      = %d\n", (int)sizeof(struct foo));
    printf("offsetof(struct foo, c) = %d\n", (int)offsetof(struct foo, c));
    printf("offsetof(struct foo, x) = %d\n", (int)offsetof(struct foo, x));
    printf("arr[0].x = %d\n", arr[0].x);
    printf("arr[1].x = %d\n", arr[1].x);
    printf("p0 = %p\n", (void*)p0);
    printf("p1 = %p\n", (void*)p1);
    printf("*p0 = %d\n", *p0);
    printf("*p1 = %d\n", *p1);
    return 0;
}

On x86 Ubuntu with gcc 4.5.2, it produces the following output:

sizeof(struct foo)      = 5
offsetof(struct foo, c) = 0
offsetof(struct foo, x) = 1
arr[0].x = 10
arr[1].x = 20
p0 = 0xbffc104f
p1 = 0xbffc1054
*p0 = 10
*p1 = 20

On SPARC Solaris 9 with gcc 4.5.1, it produces the following:

sizeof(struct foo)      = 5
offsetof(struct foo, c) = 0
offsetof(struct foo, x) = 1
arr[0].x = 10
arr[1].x = 20
p0 = ffbff317
p1 = ffbff31c
Bus error

In both cases, the program is compiled with no extra options, just gcc packed.c -o packed.

(A program that uses a single struct rather than array doesn't reliably exhibit the problem, since the compiler can allocate the struct on an odd address so the x member is properly aligned. With an array of two struct foo objects, at least one or the other will have a misaligned x member.)

(In this case, p0 points to a misaligned address, because it points to a packed int member following a char member. p1 happens to be correctly aligned, since it points to the same member in the second element of the array, so there are two char objects preceding it -- and on SPARC Solaris the array arr appears to be allocated at an address that is even, but not a multiple of 4.)

When referring to the member x of a struct foo by name, the compiler knows that x is potentially misaligned, and will generate additional code to access it correctly.

Once the address of arr[0].x or arr[1].x has been stored in a pointer object, neither the compiler nor the running program knows that it points to a misaligned int object. It just assumes that it's properly aligned, resulting (on some systems) in a bus error or similar other failure.

Fixing this in gcc would, I believe, be impractical. A general solution would require, for each attempt to dereference a pointer to any type with non-trivial alignment requirements either (a) proving at compile time that the pointer doesn't point to a misaligned member of a packed struct, or (b) generating bulkier and slower code that can handle either aligned or misaligned objects.

I've submitted a gcc bug report. As I said, I don't believe it's practical to fix it, but the documentation should mention it (it currently doesn't).

UPDATE: As of 2018-12-20, this bug is marked as FIXED. The patch will appear in gcc 9 with the addition of a new -Waddress-of-packed-member option, enabled by default.

When address of packed member of struct or union is taken, it may result in an unaligned pointer value. This patch adds -Waddress-of-packed-member to check alignment at pointer assignment and warn unaligned address as well as unaligned pointer

I've just built that version of gcc from source. For the above program, it produces these diagnostics:

c.c: In function ‘main’:
c.c:10:15: warning: taking address of packed member of ‘struct foo’ may result in an unaligned pointer value [-Waddress-of-packed-member]
   10 |     int *p0 = &arr[0].x;
      |               ^~~~~~~~~
c.c:11:15: warning: taking address of packed member of ‘struct foo’ may result in an unaligned pointer value [-Waddress-of-packed-member]
   11 |     int *p1 = &arr[1].x;
      |               ^~~~~~~~~

connecting to phpMyAdmin database with PHP/MySQL

Set up a user, a host the user is allowed to talk to MySQL by using (e.g. localhost), grant that user adequate permissions to do what they need with the database .. and presto.

The user will need basic CRUD privileges to start, that's sufficient to store data received from a form. The rest of the permissions are self explanatory, i.e. permission to alter tables, etc. Give the user no more, no less power than it needs to do its work.

How to make Bootstrap carousel slider use mobile left/right swipe

Checked solution is not accurate, sometimes mouse-right-click triggers right-swipe. after trying different plugins for swipe i found an almost perfect one.

touchSwipe

i said "almost" because this plugin does not support future elements. so we would have to reinitialize the swipe call when the swipe content is changed by ajax or something. this plugin have lots of options to play with touch events like multi-finger-touch,pinch etc.

http://labs.rampinteractive.co.uk/touchSwipe/demos/index.html

solution 1 :

$("#myCarousel").swipe( {
            swipe:function(event, direction, distance, duration, fingerCount, fingerData) {

                if(direction=='left'){
                    $(this).carousel('next');
                }else if(direction=='right'){
                    $(this).carousel('prev');
                }

            }
        });

solution 2:(for future element case)

function addSwipeTo(selector){
            $(selector).swipe("destroy");
            $(selector).swipe( {
                swipe:function(event, direction, distance, duration, fingerCount, fingerData) {
                    if(direction=='left'){
                        $(this).carousel('next');
                    }else if(direction=='right'){
                        $(this).carousel('prev');
                    }
                }
            });
}
addSwipeTo("#myCarousel");

Force “landscape” orientation mode

screen.orientation.lock('landscape');

Will force it to change to and stay in landscape mode. Tested on Nexus 5.

http://www.w3.org/TR/screen-orientation/#examples

Launch an app on OS X with command line

With applescript:

tell application "Firefox" to activate