效果圖例如以下：

package com.test;
import java.security.MessageDigest;

public class MD5 {

 // MD5加碼。32位
 public static String MD5(String inStr) {
  MessageDigest md5 = null;
  try {
   md5 = MessageDigest.getInstance("MD5");
  } catch (Exception e) {
   System.out.println(e.toString());
   e.printStackTrace();
   return "";
  }
  char[] charArray = inStr.toCharArray();
  byte[] byteArray = new byte[charArray.length];

  for (int i = 0; i < charArray.length; i++)
   byteArray[i] = (byte) charArray[i];

  byte[] md5Bytes = md5.digest(byteArray);

  StringBuffer hexValue = new StringBuffer();

  for (int i = 0; i < md5Bytes.length; i++) {
   int val = ((int) md5Bytes[i]) & 0xff;
   if (val < 16)
    hexValue.append("0");
   hexValue.append(Integer.toHexString(val));
  }

  return hexValue.toString();
 }

 // 可逆的加密算法
 public static String KL(String inStr) {
  // String s = new String(inStr);
  char[] a = inStr.toCharArray();
  for (int i = 0; i < a.length; i++) {
   a[i] = (char) (a[i] ^ 't');
  }
  String s = new String(a);
  return s;
 }

 // 加密后解密
 public static String JM(String inStr) {
  char[] a = inStr.toCharArray();
  for (int i = 0; i < a.length; i++) {
   a[i] = (char) (a[i] ^ 't');
  }
  String k = new String(a);
  return k;
 }

 // 測(cè)試主函數(shù)
 public static void main(String args[]) {
  String s = new String("123456");
  System.out.println("原始：" + s);
  System.out.println("MD5后：" + MD5(s));
  System.out.println("MD5后再加密：" + KL(MD5(s)));
  System.out.println("解密為MD5后的：" + JM(KL(MD5(s))));
  System.out.println("加密的：" + KL(s));
  System.out.println("解密的：" + JM(KL(s)));
  
 }

}