生成MD5码，并对MD5码进行二次加密和解密

package com.util.md5;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
/**
 *
 * @describe 实现将生成的MD5码进行加密和解密，
 * @author zhutianpeng
 *
 */
public class UtilMD5 {
    private UtilMD5(){} //避免生成对象，实现静态访问
                                                  
    /**
     * @describe 实现MD5码进行二次加密后的编码
     * @param str
     * @return secondCode
     */
    public static String getConcertCodeMD5(String str){
        String firstCode = string2MD5(str);
        String secondCode = convertMD5(firstCode);
        return secondCode;
    }
                                                  
    /**
     * @describe 实现MD5码进行二次加密后的编码进行解密所生成的MD5码
     * @param str
     * @return secondCode
     */
    public static String getConcertEncodeMD5(String str){
        String firstCode = convertMD5(str);
        String secondCode = string2MD5(firstCode);
        return secondCode;
    }
                                                  
    /***
     * MD5加码 生成32位md5码
     */
    private static String string2MD5(String str){
                                                      
        MessageDigest md5 = null;
        try {
            md5 = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
            System.out.println("【MD5算法异常，生成MD5码失败...】");
            return "";
        }
        char[] charArray = str.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();
                                                
    }
                                                
    /**
     * 加密解密算法 执行一次加密，两次解密
     */
    private static String convertMD5(String str){
                                                
        char[] temp = str.toCharArray();
        for (int i = 0; i < temp.length; i++){
            temp[i] = (char) (temp[i] ^ 'z');
        }
        String myStr = new String(temp);
        return myStr;
    }
}


public class Test {
    public static void main(String[] args) {
                                        
        String a = "aaa";
        System.out.println("MD5码加密："+UtilMD5.getConcertCodeMD5(a));
        System.out.println("MD5码加密后解密："+UtilMD5.getConcertEncodeMD5(UtilMD5.getConcertCodeMD5(a)));
    }
}