AP CSA UNIT 3

Which of the following correctly accesses the last element of an array `arr` in Java?

• `arr[arr.length]`

• `arr[arr.length - 1]`

• `arr[-1]`

• `arr[length - 1]`

What is the output of the following code? ```java int[] numbers = {2, 4, 6, 8, 10}; System.out.println(numbers[2]); ```

• 2

• 4

• 6

• 8

Which loop is best for iterating through an array when you don’t need to modify the elements?

• `for` loop

• `while` loop

• Enhanced `for` loop

• Do-while loop

What does the following method return? ```java public int sumArray(int[] arr) { int sum = 0; for (int i = 0; i < arr.length; i++) { sum += arr[i]; } return sum; } ```

• The product of all elements in the array

• The sum of all elements in the array

• The length of the array

• The largest element in the array

Which of the following is true about polymorphism?

• It allows a method to have multiple definitions with different parameter types.

• It enables an object to take many forms and execute overridden methods of a subclass.

• It ensures that an object’s data is private and can only be accessed through methods.

• It allows a class to inherit methods and fields from another class.

What happens when you compare two String objects using `==` instead of `.equals()`?

• It compares the actual content of the strings.

• It always returns `true`.

• It compares the memory addresses of the objects.

• It throws a runtime exception.

How many times will the following nested loop execute? ```java for (int i = 0; i < 3; i++) { for (int j = 0; j < 4; j++) { System.out.println("Hello"); } } ```

• 3

• 4

• 7

• 12

Which of the following correctly implements an algorithm to find the sum of an array?

• `int sum = 1; for (int i = 0; i < arr.length; i++) { sum *= arr[i]; }`

• `int sum = 0; for (int num : arr) { sum += num; }`

• `int sum = 0; for (int i = 1; i <= arr.length; i++) { sum += arr[i]; }`

• `int sum = arr[0]; for (int i = 1; i < arr.length; i++) { sum += arr[i]; }`

Which statement best describes the use of the `equals()` method in Java?

• It checks whether two objects are identical in memory.

• It compares the content of two objects for equality.

• It is only used for comparing integer values.

• It can be used to compare primitive data types directly.

What is the purpose of the `return` statement inside a loop?

• It continues to the next iteration of the loop.

• It stops the execution of the loop immediately and exits the method.

• It restarts the loop from the beginning.

• It has no effect on loop execution.