MD5 encryption tool class

package cn.itcast.utils;

import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public  class MD5Utils {
     /**
     * Use md5 algorithm for encryption
     */
    public static String md5(String plainText) {
        byte[] secretBytes = null;
        try {
            secretBytes = MessageDigest.getInstance("md5").digest(
                    plainText.getBytes());
        } catch (NoSuchAlgorithmException e) {
             throw  new RuntimeException("There is no md5 algorithm!" );
        }
        String md5code = new BigInteger(1, secretBytes).toString(16); // Hexadecimal number
         // If the generated number is less than 32 digits, you need to add 0 in front 
        for ( int i = 0; i < 32 - md5code.length (); i++ ) {
            md5code = "0" + md5code;
        }
        return md5code;
    }

    public static void main(String[] args) {
        System.out.println(md5("1234"));
    }

}