AP CSA Arrays and ArrayLists 2

Question 1

How do you find the number of elements in an ArrayList called `list`?

Accepted Answer

list.size()

Answer

ArrayList uses the size() method (not length) to return the number of elements it contains.

Question 2

What is the result of `int[] arr = {3, 1, 4, 1, 5}; System.out.println(arr[2]);`?

Accepted Answer

4

Answer

arr[2] accesses the third element (index 2), which is 4 in the array {3, 1, 4, 1, 5}.

Question 3

Which loop is most commonly used to iterate over every element in an array in AP CSA?

Accepted Answer

for-each (enhanced for loop)

Answer

The enhanced for loop (for-each) is idiomatic for iterating all elements when the index is not needed.

Question 4

What does `list.remove(0)` do to an ArrayList?

Accepted Answer

Removes the element at index 0

Answer

When passed an int, ArrayList's remove(int index) removes the element at that index, shifting remaining elements left.

Question 5

Which of these correctly initializes a 2D array with 3 rows and 4 columns?

Accepted Answer

int[][] grid = new int[3][4];

Answer

The syntax `new int[rows][columns]` creates a 2D array; `new int[3][4]` gives 3 rows and 4 columns.

AP CSA - Advanced Placement Computer Science A Practice Test