AP Computer Science Exam Question

Consider the following code snippet:

import java.util.Random;

public class RandomClassExample {
    public static void main(String[] args) {
        Random rand = new Random();
        int[] numbers = new int[5];

        for (int i = 0; i < 5; i++) {
            numbers[i] = rand.nextInt(10);
        }
        
        System.out.println("Generated Numbers:");
        for (int num : numbers) {
            System.out.println(num);
        }
    }
}

Explain the purpose and functionality of the Random class in the given code, and describe the output produced by the code. Also, discuss how changing the value inside rand.nextInt(10) in the for loop affects the output.

Answer

The Random class in Java provides functionalities to generate random numbers. It is imported using the line import java.util.Random;.

In the given code snippet, an instance of the Random class is created with the line Random rand = new Random();. This instance is used to generate random numbers later on.

An array of integers called numbers with a length of 5 is declared with the line int[] numbers = new int[5];. This array will store the random numbers generated.

Inside the for loop, the line numbers[i] = rand.nextInt(10); generates a random number between 0 (inclusive) and 10 (exclusive) using the method nextInt(10) of the Random class. This random number is then assigned to the i-th index of the numbers array.

The line System.out.println("Generated Numbers:"); prints the text "Generated Numbers:" to the console.

The subsequent for loop iterates through each element in the numbers array, printing each number on a separate line with the line System.out.println(num);.

Therefore, the output produced by the code will be something like:

Generated Numbers:
2
7
0
9
4

Changing the value inside rand.nextInt(10) affects the range of random numbers generated. The argument passed to nextInt() specifies an exclusive upper bound for the random numbers generated. In the given code, the upper bound is 10. If we were to change it to a different value, for example, rand.nextInt(50), the random numbers generated would be between 0 (inclusive) and 50 (exclusive).

If we change the line to numbers[i] = rand.nextInt(5);, the random numbers generated would be between 0 (inclusive) and 5 (exclusive). Therefore, the possible generated numbers would be 0, 1, 2, 3, and 4. The output produced would vary accordingly.