Java SecureRandom nextInt()

In this guide, you will learn about the SecureRandom nextInt() method in Java programming and how to use it with an example.

1. SecureRandom nextInt() Method Overview

Definition:

The nextInt(int bound) method is used to generate a cryptographically strong random integer between 0 (inclusive) and the specified bound (exclusive).

Syntax:

public int nextInt(int bound)

Parameters:

- bound: The upper bound (exclusive) on the random number to be returned. Must be positive.

Key Points:

- The nextInt(int bound) method is used to generate a cryptographically strong random integer between 0 (inclusive) and the specified bound (exclusive).

- Throws IllegalArgumentException if the bound is not positive.

- SecureRandom is preferable over the Random class when higher quality randomness is required, especially in security-sensitive applications.

- The SecureRandom instance can be seeded using a user-provided seed or automatically by the system.

- This method may block as entropy is being gathered, especially if it is invoked shortly after the instance is created.

2. SecureRandom nextInt() Method Example

import java.security.SecureRandom;

public class SecureRandomExample {

    public static void main(String[] args) {
        // Create a SecureRandom object
        SecureRandom secureRandom = new SecureRandom();

        // Generate random integers within a given bound
        int randomInt1 = secureRandom.nextInt(100); // bound is 100
        int randomInt2 = secureRandom.nextInt(1000); // bound is 1000

        // Print the generated random integers
        System.out.println("Random Integer within 0 to 100: " + randomInt1);
        System.out.println("Random Integer within 0 to 1000: " + randomInt2);
    }
}

Output:

Random Integer within 0 to 100: 63
Random Integer within 0 to 1000: 827
(Note: The actual output may vary each time the program is executed as the numbers are randomly generated.)

Explanation:

In this example, a SecureRandom object is created, and two random integers within different bounds are generated using the nextInt(int bound) method. The generated random integers are then printed to the console, demonstrating the method's ability to produce cryptographically strong random integers within a specified range.