我实现的MD5加密类

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package org.goodpp.website.security;

import java.security.MessageDigest;

/**
*RFC 1321中，给出了Test suite用来检验你的实现是否正确：
*MD5 ("") = d41d8cd98f00b204e9800998ecf8427e
*MD5 ("a") = 0cc175b9c0f1b6a831c399e269772661
*MD5 ("abc") = 900150983cd24fb0d6963f7d28e17f72
*MD5 ("message digest") = f96b697d7cb7938d525a2f31aaf161d0
*MD5 ("abcdefghijklmnopqrstuvwxyz") = c3fcd3d76192e4007dfb496cca67e13b
*
* @author goodpp@126.com
*/
public class MD5Demo {

private static String algorithm = "MD5";

public static String encryptStr(String str, String algorithm) {
  byte[] unencryptStr = str.getBytes();
  MessageDigest md = null;
  try {
   md = MessageDigest.getInstance(algorithm);
  } catch(Exception e) {
   e.printStackTrace();
  }
  md.reset();
  md.update(unencryptStr);
  byte[] encryptStr = md.digest();
        StringBuffer buf = new StringBuffer();

        for (int i = 0; i < encryptStr.length; i++) {
            if ((encryptStr[i] & 0xff) < 0x10) {
                buf.append("0");
            }

            buf.append(Long.toString(encryptStr[i] & 0xff, 16));
        }
  return buf.toString();
}

public static void main(String[] args) {
  String s = MD5Demo.encryptStr("abcdefghijklmnopqrstuvwxyz", MD5Demo.algorithm);
  System.out.println(s);
}
}