import java.security.MessageDigest; 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)); } }