AP Computer Science Exam Question

ArrayList Methods and Operations

Consider the following Java code:

import java.util.ArrayList;

public class ArrayListOperations {
    
    public static void main(String[] args) {
        ArrayList<Integer> numbers = new ArrayList<>();
        
        numbers.add(5);
        numbers.add(7);
        numbers.add(4);
        numbers.add(1);
        numbers.add(9);
        
        System.out.println("Original list: " + numbers);
        
        numbers.set(2, 6);
        numbers.remove(3);
        numbers.add(8);
        
        System.out.println("Updated list: " + numbers);
        
        System.out.println("Sum of the numbers in the list: " + calculateSum(numbers));
        System.out.println("Largest number in the list: " + findLargest(numbers));
        System.out.println("Smallest number in the list: " + findSmallest(numbers));
        System.out.println("Average of the numbers in the list: " + calculateAverage(numbers));
    }
    
    // Method to calculate the sum of numbers in the list
    public static int calculateSum(ArrayList<Integer> list) {
        int sum = 0;
        for (int num : list) {
            sum += num;
        }
        return sum;
    }

    // Method to find the largest number in the list
    public static int findLargest(ArrayList<Integer> list) {
        int largest = Integer.MIN_VALUE;
        for (int num : list) {
            if (num > largest) {
                largest = num;
            }
        }
        return largest;
    }
    
    // Method to find the smallest number in the list
    public static int findSmallest(ArrayList<Integer> list) {
        int smallest = Integer.MAX_VALUE;
        for (int num : list) {
            if (num < smallest) {
                smallest = num;
            }
        }
        return smallest;
    }
    
    // Method to calculate the average of numbers in the list
    public static double calculateAverage(ArrayList<Integer> list) {
        int sum = calculateSum(list);
        return (double) sum / list.size();
    }
}

1. What is the output of the above Java code?

Answer:

The output of the above Java code will be:

Original list: [5, 7, 4, 1, 9]
Updated list: [5, 7, 6, 9, 8]
Sum of the numbers in the list: 35
Largest number in the list: 9
Smallest number in the list: 5
Average of the numbers in the list: 7.0

Explanation:

The given code demonstrates various methods and operations that can be performed on an ArrayList in Java. Here's a step-by-step breakdown of the code:

• An empty ArrayList called numbers is created to store integers.
• The add() method is used to add integers to the numbers list: 5, 7, 4, 1, and 9.
• The println() method is used to print the original list: [5, 7, 4, 1, 9].
• The set() method is used to replace the element at index 2 with the value 6.
• The remove() method is used to remove the element at index 3.
• The add() method is used to add the value 8 to the end of the list.
• The println() method is used to print the updated list: [5, 7, 6, 9, 8].
• The calculateSum() method is called to calculate the sum of the numbers in the list, which returns 35.
• The findLargest() method is called to find the largest number in the list, which returns 9.
• The findSmallest() method is called to find the smallest number in the list, which returns 5.
• The calculateAverage() method is called to calculate the average of the numbers in the list, which returns 7.0.

Finally, the respective values are printed using the println() method.