java 实现MD5加密算法的简单实例

import java.security.NoSuchAlgorithmException;   public class MD5HashUtil  {  private MessageDigest md = null;  private static MD5HashUtil md5 = null;  private static final char[] hexChars ={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};     /**   * Constructor is private so you must use the getInstance method   */    private MD5HashUtil() throws NoSuchAlgorithmException    {     md = MessageDigest.getInstance("MD5");    }    /**   * This returns the singleton instance   */   public static MD5HashUtil getInstance()throws NoSuchAlgorithmException    {      if (md5 == null)      {       md5 = new MD5HashUtil();     }     return (md5);    }   public static String hashCode(String dataToHash) throws NoSuchAlgorithmException{   return getInstance().hashData(dataToHash.getBytes());   }   public static String hashCode(byte[] dataToHash) throws NoSuchAlgorithmException{   return getInstance().hashData(dataToHash);   }  public String hashData(byte[] dataToHash) {     return hexStringFromBytes((calculateHash(dataToHash))).toLowerCase();  }  private byte[] calculateHash(byte[] dataToHash)  {     md.update(dataToHash, 0, dataToHash.length);     return (md.digest());   }  public String hexStringFromBytes(byte[] b)  {    String hex = "";    int msb;    int lsb = 0;    int i;    // MSB maps to idx 0    for (i = 0; i < b.length; i++)    {     msb = ((int)b[i] & 0x000000FF) / 16;     lsb = ((int)b[i] & 0x000000FF) % 16;      hex = hex + hexChars[msb] + hexChars[lsb];     }     return(hex);    }   public static void main(String args[]) throws NoSuchAlgorithmException  {  String string = "my name is zhangli";  System.out.println(string);  System.out.println(hashCode(string));  }  }