Java SecureRandom nextBytes()

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

1. SecureRandom nextBytes() Method Overview


The nextBytes() method of the SecureRandom class in Java is used to generate a user-specified number of random bytes. This method is primarily used in cryptographic operations and other areas where high-quality randomness is essential.


public void nextBytes(byte[] bytes)


- bytes: The byte array that the random bytes should be placed in.

Key Points:

- The nextBytes() method populates the byte array with random bytes, the length of which is determined by the length of the input byte array.

- SecureRandom is preferable over the Random class when a higher quality of randomness is required.

- SecureRandom instances can be seeded using user-provided seeds or automatically by the system.

2. SecureRandom nextBytes() Method Example

import java.util.Arrays;

public class SecureRandomExample {

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

        // Create a byte array
        byte[] randomBytes = new byte[16];

        // Generate random bytes and place them into the byte array

        // Print the generated random bytes
        System.out.println("Generated Random Bytes: " + Arrays.toString(randomBytes));


Generated Random Bytes: [21, -68, 40, 37, -112, 44, -36, -113, 48, 75, -54, 56, -67, -45, 62, 23]
(Note: The actual output may vary each time the program is executed as the numbers are randomly generated.)


In this example, a SecureRandom object is created, and a byte array of length 16 is initialized. The nextBytes() method is then used to populate this byte array with random bytes. The populated byte array is printed to the console, showcasing the ability of the nextBytes() method to generate high-quality random bytes.