AP CSA Unit 4 Day 12: Array Out Of Bounds

February 6, 2026

Unit 4, Data Collections • Cycle 2

Day 12 Advanced Practice • Harder Difficulty

Focus: Array Out of Bounds Hard Array Out of Bounds

Advanced Practice Question

Format: Array Out of Bounds

Which line causes ArrayIndexOutOfBoundsException?

int[] arr = new int[5];

arr[0] = 1;    // Line 1
arr[4] = 5;    // Line 2
arr[5] = 6;    // Line 3

Difficulty: Hard | Topic: Array Out of Bounds | Cycle: 2 (Advanced)

Why This Answer?

Array indices are 0 to length-1. For arr.length=5, valid indices are 0-4. arr[5] is out of bounds.

Common Mistake

Watch Out!

Forgetting arrays are 0-indexed, so last valid index is length-1.

AP Exam Strategy

Array of size N: valid indices are 0 to N-1. Index N is out of bounds.

This Cycle 2 HARD question tests array out of bounds. Review Unit 4 concepts to build mastery of data collections.

Cycle 2 questions prepare you for the hardest AP CSA exam questions.