The nextBytes() method of java.security.SecureRandom class is used to generate a user-specified number of random bytes.
If a call to setSeed had not occurred previously, the first call to this method forces this SecureRandom object to seed itself. This self-seeding will not occur if setSeed was previously called.
Syntax:
public void nextBytes(byte[] bytes)
Parameters: This method takes the array to be filled in with random bytes as parameter .
Note:
- The programs will not run on online IDE.
- Every time Secure Random class will generate random output.
Below are the examples to illustrate the nextBytes() method:
Example 1:
// Java program to demonstrate// nextBytes() method import java.security.*;import java.util.*; public class GFG1 { public static void main(String[] argv) { try { // creating the object of SecureRandom SecureRandom sr = SecureRandom.getInstance("SHA1PRNG"); // Declaring the string variable String str = "Tajmahal"; // Declaring the byte Array // converting string into byte byte[] b = str.getBytes(); // printing the byte array System.out.println("Byte array before operation : " + Arrays.toString(b)); // generating user-specified number of random bytes // using nextBytes() method sr.nextBytes(b); // printing the new byte array System.out.println("Byte array after operation : " + Arrays.toString(b)); } catch (NoSuchAlgorithmException e) { System.out.println("Exception thrown : " + e); } catch (ProviderException e) { System.out.println("Exception thrown : " + e); } }} |
Output:
Byte array before operation : [84, 97, 106, 109, 97, 104, 97, 108] Byte array after operation : [-79, -110, -18, -31, -54, -36, 63, -61]
Note: The following program throws the following Exception on GeeksForGeeks IDE but it will run efficiently on any Command Prompt(JDK)
Exception thrown : java.security.ProviderException: init failed
Example 2:
// Java program to demonstrate// nextBytes() method import java.security.*;import java.util.*; public class GFG1 { public static void main(String[] argv) { try { // creating the object of SecureRandom SecureRandom sr = new SecureRandom(new byte[] { 1, 2, 3, 4 }); // Declaring the string variable String str = "Tajmahal"; // Declaring the byte Array b byte[] b = str.getBytes(); // printing the byte array System.out.println("Byte array before operation : " + Arrays.toString(b)); // generating user-specified number of random bytes // using nextBytes() method sr.nextBytes(b); // printing the new byte array System.out.println("Byte array after operation : " + Arrays.toString(b)); } catch (ProviderException e) { System.out.println("Exception thrown : " + e); } }} |
Output:
Byte array before operation : [84, 97, 106, 109, 97, 104, 97, 108] Byte array after operation : [-14, 77, 123, 121, 116, 50, -89, -86]
