package test;

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

public class MD5Util {

    //第一种实现

    public final static String MD5(String s) {

        char hexDigits[]={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};

        try {

            byte[] btInput = s.getBytes();

            // 获得MD5摘要算法的 MessageDigest 对象

            MessageDigest mdInst = MessageDigest.getInstance("MD5");

            // 使用指定的字节更新摘要

            mdInst.update(btInput);

            // 获得密文

            byte[] md = mdInst.digest();

            // 把密文转换成十六进制的字符串形式

            int j = md.length;

            char str[] = new char[j * 2];

            int k = 0;

            for (int i = 0; i < j; i++) {

                byte byte0 = md[i];

                str[k++] = hexDigits[byte0 >>> 4 & 0xf];

                str[k++] = hexDigits[byte0 & 0xf];

            }

            return new String(str);

        } catch (Exception e) {

            e.printStackTrace();

            return null;

        }

    }

    //第二种实现

    public final static String MD(String str) {//项目中的

        try {

              MessageDigest md5 = MessageDigest.getInstance("MD5");

              md5.update(str.getBytes());

              byte b[] = md5.digest();

              StringBuffer sb = new StringBuffer("");

              for (int n = 0; n < b.length; n++) {

                int i = b[n];

                if (i < 0) i += 256;

                if (i < 16) sb.append("0");

                sb.append(Integer.toHexString(i));

              }

              return sb.toString();  //32位加密

            } catch (NoSuchAlgorithmException e) {

              e.printStackTrace();

              return null;

            }

    }

    public static void main(String[] args) {

        System.out.println(MD5Util.MD5("111"));

        System.out.println(MD5Util.MD("111"));

    }

}