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MessageDigest reset() method in Java with Examples

  • Last Updated : 06 Aug, 2021

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
// toString() 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
// toString() 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–
 

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