MessageDigest reset() method in Java with Examples

The reset() method of java.security.MessageDigest class is used to reset current message digest value to default message digest value of this MessageDisgest object.
Syntax:

public void reset()

Return Value: This method has nothing to return.
Below are the examples to illustrate the reset() method:
Example 1:

Java

// Java program to demonstrate
// reset() method

import java.security.*;
import java.nio.*;
import java.util.*;

public class GFG1 {
    public static void main(String[] argv)
    {
        try {

            byte[] barr = { 10, 20, 30, 40 };

            // creating object of MessageDigest
            MessageDigest msd1
                = MessageDigest.getInstance("MD5");

            // display the digest value before Updation
            System.out.println("MessageDigest before update : "
                               + (ByteBuffer.wrap(
                                      msd1.digest()))
                                     .getShort());

            // creating object of ByteBuffer
            // and allocating size capacity
            ByteBuffer bb = ByteBuffer.wrap(barr);

            // update MessageDigest value
            // using update() method
            msd1.update(bb);

            // display the digest value before Updation
            System.out.println("\nMessageDigest after update : "
                               + (ByteBuffer.wrap(
                                      msd1.digest()))
                                     .getShort());

            // reset MessageDigest value
            // using reset() method
            msd1.reset();

            // display the digest value after reset
            System.out.println("\nMessageDigest after reset : "
                               + (ByteBuffer.wrap(
                                      msd1.digest()))
                                     .getShort());
        }

        catch (NoSuchAlgorithmException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (ProviderException e) {

            System.out.println("Exception thrown : " + e);
        }
    }
}

Output:

MessageDigest before update : -11235

MessageDigest after update : 30835

MessageDigest after reset : -11235

Example 2:

Java

// Java program to demonstrate
// reset() method

import java.security.*;
import java.nio.*;
import java.util.*;

public class GFG1 {
    public static void main(String[] argv)
    {
        try {

            byte[] barr = { 10, 20, 30, 40 };

            // creating object of MessageDigest
            MessageDigest msd1
                = MessageDigest.getInstance("SHA-256");

            // display the digest value before Updation
            System.out.println("MessageDigest before update : "
                               + (ByteBuffer.wrap(
                                      msd1.digest()))
                                     .getShort());

            // creating object of ByteBuffer
            // and allocating size capacity
            ByteBuffer bb = ByteBuffer.wrap(barr);

            // update MessageDigest value
            // using update() method
            msd1.update(bb);

            // display the digest value before Updation
            System.out.println("\nMessageDigest after update : "
                               + (ByteBuffer.wrap(
                                      msd1.digest()))
                                     .getShort());

            // reset MessageDigest value
            // using reset() method
            msd1.reset();

            // display the digest value after reset
            System.out.println("\nMessageDigest after reset : "
                               + (ByteBuffer.wrap(
                                      msd1.digest()))
                                     .getShort());
        }

        catch (NoSuchAlgorithmException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (ProviderException e) {

            System.out.println("Exception thrown : " + e);
        }
    }
}

Output:

MessageDigest before update : -7248

MessageDigest after update : 24403

MessageDigest after reset : -7248

Reference:
https://docs.oracle.com/javase/9/docs/api/java/security/MessageDigest.html#reset--

MessageDigest reset() method in Java with Examples

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