What is a NullPointerException, and how do I fix it?

A NullPointerException (NPE) is a common runtime error in Java and other programming languages. It occurs when you try to access or manipulate an object that has not been initialized (i.e., its value is null). To fix it:

1. Identify the null reference causing the issue.
2. Check the code to ensure that the object is properly initialized before using it.
3. Use conditional checks or optional handling (e.g., if statements or the Optional class in Java) to avoid null references.
4. Implement error handling or exception catching to gracefully handle null situations if they cannot be avoided.