EC
ArrayIndexOutOfBoundsException
JavaFATALCommonArray

Array index out of bounds

Quick Answer

Check array.length before indexing, or use enhanced for-loop to avoid manual indexing.

What this means

Thrown when code tries to access an array element with an index that is negative or >= array.length.

Why it happens
  1. 1Index equals array.length (off-by-one)
  2. 2Negative index from a subtraction result

Fix

Bounds check before access

Bounds check before access
if (i >= 0 && i < arr.length) {
    System.out.println(arr[i]);
}

Why this works

Explicit range guard prevents the JVM from throwing the exception.

Code examples
Triggerjava
int[] a = {1, 2, 3};
int x = a[3]; // ArrayIndexOutOfBoundsException
Safe accessjava
int get(int[] a, int i) {
    return (i >= 0 && i < a.length) ? a[i] : -1;
}
Use List insteadjava
List<Integer> list = List.of(1, 2, 3);
// list.get(3) throws IndexOutOfBoundsException with better message
Sources
Official documentation ↗

Java SE Documentation

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