md5的一些用法

package md5;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
/*
 * MD5 算法
*/
public class MD5 {
    
    // 全局数组
    private final static String[] strDigits = { "0", "1", "2", "3", "4", "5",
            "6", "7", "8", "9", "a", "b", "c", "d", "e", "f","+","-" };

    public MD5() {
    }

    // 返回形式为数字跟字符串
    private static String byteToArrayString(byte bByte) {
        int iRet = bByte;
        // System.out.println("iRet="+iRet);
        if (iRet < 0) {
            iRet += 256;
        }
        int iD1 = iRet / 16;
        int iD2 = iRet % 16;
        return strDigits[iD1] + strDigits[iD2];
    }

    // 返回形式只为数字
    private static String byteToNum(byte bByte) {
        int iRet = bByte;
        System.out.println("iRet1=" + iRet);
        if (iRet < 0) {
            iRet += 256;
        }
        return String.valueOf(iRet);
    }

    // 转换字节数组为16进制字串
    private static String byteToString(byte[] bByte) {
        StringBuffer sBuffer = new StringBuffer();
        for (int i = 0; i < bByte.length; i++) {
            sBuffer.append(byteToArrayString(bByte[i]));
        }
        return sBuffer.toString();
    }

    public static String GetMD5Code(String strObj) {
        String resultString = null;
        try {
            resultString = new String(strObj);
            MessageDigest md = MessageDigest.getInstance("MD5");
            // md.digest() 该函数返回值为存放哈希值结果的byte数组
            resultString = byteToString(md.digest(strObj.getBytes()));
        } catch (NoSuchAlgorithmException ex) {
            ex.printStackTrace();
        }
        return resultString;
    }
    // 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;   
    }   
    public static void main(String[] args) {
        MD5 getMD5 = new MD5();
        String str="a";
        System.out.println(getMD5.GetMD5Code(str));
        System.out.println(getMD5.KL(str));
        System.out.println(getMD5.JM(KL(str)));
    }
}