MD5加密解密过程

package com.kd.md5.demo;

import java.security.MessageDigest;

public class MyMd5Demo {
	public static void main(String[] args) {
		String string = "中华人民共和国万岁";
		System.out.println("原文:"+string);
		String fun1 = fun1(string);
		System.out.println("加密:" + fun1);
		//加密一次要解密两次
		String string2 = fun2(fun2(string));
		System.out.println("解密后:" + string2);
	}
	//MD5加密
	public static String fun1(String str) {
		if (str==null) {
			return null;
		}
		try {
			//获取MessageDigest对象
			MessageDigest md = MessageDigest.getInstance("MD5");
			char[] array = str.toCharArray();
			//将获取的char字符数组转换成byte型数组
			byte by[] = new byte[array.length];
			for (int i = 0; i < array.length; i++) {
				by[i] = (byte) array[i];
			}
			//获取密文，再将其转换成16进制的数
			byte mdByte[] = md.digest(by);
			StringBuffer mdvalue = new StringBuffer();

			for (int i = 0; i < mdByte.length; i++) {
				int val = ((int) mdByte[i] & 0xff);
				if (val < 16) {
					mdvalue.append("0");
				}
				mdvalue.append(Integer.toHexString(val));
			}
			return mdvalue.toString();
		} catch (Exception e) {
			e.printStackTrace();
		}
		return null;
	}
	//MD5解密
	public static String fun2(String str) {
		if (null == str) {
			return null;
		}
		char[] array = str.toCharArray();
		for (int i = 0; i < array.length; i++) {
			array[i] = (char) (array[i] ^ 't');
		}
		String res = new String(array);
		return res;
	}
}