学步园

需要判断两张图片是否相同，可以将图片加密，通过判断加密字符串是否相等，来判断图片是否相同。

package com.wayfoon.temp;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;

import java.io.IOException;
import java.io.InputStream;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class TestMD5
{

    public static String MD5(byte[] s)
    {
        //16进制字符
        char hexDigits[] =
        { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd',
                'e', 'f' };
        try
        {
            byte[] strTemp = s;
            MessageDigest mdTemp = MessageDigest.getInstance("MD5");
            mdTemp.update(strTemp);
            byte[] md = mdTemp.digest();
            int j = md.length;
            char str[] = new char[j * 2];
            int k = 0;
            //移位 输出字符串
            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)
        {
            return null;
        }
    }

    public static void main(String[] args) throws NoSuchAlgorithmException
    {
        //计算运行需要多长时间
        long t1 = System.currentTimeMillis();
        System.out.println(t1);
        //得到文件长度
        File file = new File("E://1.bmp");
        byte[] b = new byte[(int) file.length()];
        System.out.println(file.length());
        System.out.println(System.currentTimeMillis());
        try
        {
            InputStream in = new FileInputStream("E://1.bmp");
            in.read(b);
            System.out.println(in.read());
        }
        catch (FileNotFoundException e)
        {
            e.printStackTrace();
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }

        System.out.println(TestMD5.MD5(b));

        long t2 = System.currentTimeMillis();
        System.out.println(t2);
       
        System.out.println(t2 - t1);
    }

}