All Questions

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them? What methods/tools can be used to determine the cause so that you stop the exception from causing the program ...

When discussing performance with colleagues, teaching, sending a bug report or searching for guidance on mailing lists and here on Stack Overflow, a reproducible example is often asked and always ...

I have a function foo which makes an asynchronous request. How can I return the response/result from foo? I tried returning the value from the callback, as well as assigning the result to a local ...

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to SQL injection, like in the following example: $unsafe_variable = $_POST['user_input']; ...

I need to match all of these opening tags: <p> <a href="foo"> But not these: <br /> <hr class="foo" /> I came up with this and wanted to make sure I've got it right. I am ...

I have some code and when it executes, it throws a NullReferenceException, saying: Object reference not set to an instance of an object. What does this mean, and what can I do to fix this error?

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug. Is == bad? When should it ...

I'm running a PHP script and continue to receive errors like: Notice: Undefined variable: my_variable_name in C:\wamp\www\mypath\index.php on line 10 Notice: Undefined index: my_index C:\wamp\www\...

Consider the following code: 0.1 + 0.2 == 0.3 -> false 0.1 + 0.2 -> 0.30000000000000004 Why do these inaccuracies happen?

This question attempts to collect the few pearls among the dozens of bad C++ books that are published every year. Unlike many other programming languages, which are often picked up on the go from ...

What are the technical reasons for why one shouldn't use mysql_* functions? (e.g. mysql_query(), mysql_connect() or mysql_real_escape_string())? Why should I use something else even if they work on ...

What are undefined reference/unresolved external symbol errors? What are common causes and how to fix/prevent them? Feel free to edit/add your own.

Everyone runs into syntax errors. Even experienced programmers make typos. For newcomers, it's just part of the learning process. However, it's often easy to interpret error messages such as: PHP ...

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off. This happens on page ready ...

var funcs = []; // let's create 3 functions for (var i = 0; i < 3; i++) { // and store them in funcs funcs[i] = function() { // each should log its value. console.log("My value: " + i); ...