AP CSA Unit 4 Day 20: Arraylist Remove With Wrapper

February 6, 2026

Unit 4, Data Collections • Cycle 2

Day 20 Advanced Practice • Harder Difficulty

Focus: ArrayList Remove with Wrapper Hard ArrayList Remove with Wrapper

Advanced Practice Question

Format: ArrayList Remove with Wrapper

What is the output?

ArrayList nums = new ArrayList<>();
nums.add(10);
nums.add(20);
nums.add(30);
nums.add(20);

nums.remove(1);

System.out.println(nums);

Difficulty: Hard | Topic: ArrayList Remove with Wrapper | Cycle: 2 (Advanced)

Why This Answer?

remove(1) removes the element at INDEX 1, which is 20. The list becomes [10, 30, 20]. The last 20 remains.

Common Mistake

Watch Out!

Thinking remove(1) removes the value 1, or removes all occurrences of 20.

AP Exam Strategy

For ArrayList: remove(int index) removes by index. To remove by value, use remove(Integer.valueOf(value)).

This Cycle 2 HARD question tests arraylist remove with wrapper. Review Unit 4 concepts to build mastery of data collections.

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