SecureRandom getInstance() method in Java

A SecureRandom object can be obtained using the getInstance() method in class java.security.SecureRandom. This SecureRandom object is useful in implementing the Random Number Generator (RNG) algorithm that is specified.

The getInstance() method requires a single parameter i.e. the Random Number Generator (RNG) algorithm and it returns the SecureRandom object.

A program that demonstrates this is given as follows −

Example

 Live Demo

import java.security.*;
import java.util.*;
public class Demo {
   public static void main(String[] argv) {
      try {
         SecureRandom sRandom = SecureRandom.getInstance("SHA1PRNG");
         String s = "Apple";
         byte[] arrB = s.getBytes();
         System.out.println("The Byte array before the operation is: " + Arrays.toString(arrB));
         sRandom.nextBytes(arrB);
         System.out.println("The Byte array after the operation is: " + Arrays.toString(arrB));
      } catch (NoSuchAlgorithmException e) {
         System.out.println("Error!!! NoSuchAlgorithmException");
      } catch (ProviderException e) {
         System.out.println("Error!!! ProviderException");
      }
   }
}

Output

The Byte array before the operation is: [65, 112, 112, 108, 101]
The Byte array after the operation is: [10, 60, 119, -12, -103]

Now let us understand the above program.

The getInstance() method is used to obtain the SecureRandom object sRandom. Using this, the byte array before and after the operation is displayed. A code snippet that demonstrates is given as follows −

try {
   SecureRandom sRandom = SecureRandom.getInstance("SHA1PRNG");
   String s = "Apple";
   byte[] arrB = s.getBytes();
   System.out.println("The Byte array before the operation is: " + Arrays.toString(arrB));
   sRandom.nextBytes(arrB);
   System.out.println("The Byte array after the operation is: " + Arrays.toString(arrB));
}