NullPointerException – how do I fix it?

What is NullPointerException?

NullPointerException An exception occurs when an application attempts to use a null object reference. This can occur when you are trying to call a method or access a field of an object, and the thing is, meaning it has not been initialized or has been set to null explicitly.

Causes and ways to fix them

Here are some common causes of NullPointerException and ways to fix them:

It is generally a good idea to check for null values before using object references, especially if you are not sure whether the reference has been initialized or not. This can help prevent NullPointerException errors and make your code more robust.

For example, you can use the null coalescing operator (??) in C# to return a default value if the object reference is null, or use the is operator in Java to check if an object is null before trying to use it.

// C#
string name = obj?.Name ?? "default name";

// Java
if (obj != null) {
  // use obj
} else {
  // handle null case
}