Common Java Errors That Every Developer Encounters

As a Java developer, encountering errors is an inevitable part of the journey. Some errors are so common that almost every programmer has faced them at least once. In this post, we will explore these common Java errors, understand why they occur, and how to fix them.

1. NullPointerException (NPE)

Error: This occurs when trying to access a method or field of an object that is null.

Example:

String str = null;
System.out.println(str.length()); // Causes NullPointerException

Fix: Always check for null before accessing objects.

if (str != null) {
    System.out.println(str.length());
}

2. ArrayIndexOutOfBoundsException

Error: Occurs when accessing an array index that is out of range.

Example:

int[] arr = {1, 2, 3};
System.out.println(arr[3]); // Index 3 is out of bounds

Fix: Ensure the index is within the array size.

if (index >= 0 && index < arr.length) {
    System.out.println(arr[index]);
}

3. ClassCastException

Error: Happens when trying to cast an object to an incompatible class.

Example:

Object obj = "Hello";
Integer num = (Integer) obj; // Causes ClassCastException