效果图例如以下：

package com.test;import java.security.MessageDigest;public class MD5 { // MD5加码。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; } // 測试主函数 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("解密为MD5后的：" + JM(KL(MD5(s))));  System.out.println("加密的：" + KL(s));  System.out.println("解密的：" + JM(KL(s)));   }}