package leetcode;

import java.io.IOException;

import java.math.BigInteger;

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

import java.util.UUID;

import sun.misc.BASE64Decoder;

import sun.misc.BASE64Encoder;

public class Test12 {

	public static String getId(){

		//UUID java中不重复序列

		String id = UUID.randomUUID().toString();

		//System.out.println(id);

		//得到的这个序列号很长，可以用哈希码来表示

		int hashCode = Math.abs(id.hashCode());

		return hashCode+"";

	}

	//md5加密算法,单向加密，没有解密的

		public static String md5(String str){

			byte[] bytes = null;

			try {

				bytes = MessageDigest.getInstance("md5").digest(str.getBytes());//得到MD5的实例，再将字符串加密

			} catch (NoSuchAlgorithmException e) {

				e.printStackTrace();

			}

			return new BigInteger(1,bytes).toString(16);//把字节数组转化为正的bigInteger,然后变成16进制表示

		}

		//base64算法,解密，加密

		public static String base64Encode(String str){

			BASE64Encoder baseEncode = new BASE64Encoder();

			return baseEncode.encode(str.getBytes());//加密

		}

		public static String base64Decode(String str){

			BASE64Decoder baseDecoder = new BASE64Decoder();

			try {

				return new String(baseDecoder.decodeBuffer(str));//解密

			} catch (IOException e) {

				e.printStackTrace();

			}

			return null;

		}

	public static void main(String[] args) {

		System.out.println(getId());

		System.out.println("1234加密后："+md5("1234"));

		String str = base64Encode("1234");

		System.out.println("1234加密后："+str);

		System.out.println("解密后:"+base64Decode(str));

	}

}