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]
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