password encrytion and decryption

Hi,

I want to encrypt and decrypt the password .
I have the code for encrytion but can anyone help me to get the code
for decrytion using the same API's.

I have used the following code for Encryption

****************************************************************************************************

package com.netapp.hraf.helper;

//import com.certicom.tls.provider.MessageDigest;
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
//import org.myorg.SystemUnavailableException;
import sun.misc.BASE64Encoder;
import sun.misc.CharacterEncoder;

public final class PasswordServiceHelper
{
  public static PasswordServiceHelper instance;

  public PasswordServiceHelper()
  {
  }

  public synchronized String encrypt(String plaintext) throws Exception
  {
    MessageDigest md = null;
    try
    {
      md = MessageDigest.getInstance("SHA"); //step 2
    }
    catch(NoSuchAlgorithmException e)
    {
      throw new Exception(e.getMessage());
    }
    try
    {
      md.update(plaintext.getBytes("UTF-8")); //step 3
    }
    catch(UnsupportedEncodingException e)
    {
      throw new Exception(e.getMessage());
    }

    byte raw[] = md.digest(); //step 4
    String hash = (new BASE64Encoder()).encode(raw); //step 5
    System.out.println("the password in hash is "+hash);
    return hash; //step 6
  }

  public static synchronized PasswordServiceHelper getInstance() //step
1
  {
    if(instance == null)
    {
       instance = new PasswordServiceHelper();
    }
    return instance;
  }
}

****************************************************************************************************

Thanks,
Deepa