MessageDigest使用多线程对大文件进行分片MD5

最近做一个功能用户上传文件的时候文件比对是否重复，但是文件很大的话这样子MD5会非常慢，然后网上也没有多线程的实现，就自己写了一个

参考链接
多线程复制文件
java 计算文件MD5值 大文件

package utils;


import java.io.*;

import java.security.MessageDigest;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;



public class FileMd5  {
    public static String getMD5Message(File file){

        List list = startThread(5, file.length(), file);
        StringBuilder stringBuilder = new StringBuilder();
        list.forEach(futureTask -> {
            try {
                stringBuilder.append(futureTask.get());
            } catch (InterruptedException | ExecutionException e) {
                e.printStackTrace();
            }
        });
        return FileMd5Util.getMD5String(stringBuilder.toString());
    }

    public static void main(String[] args) {
        long start = System.currentTimeMillis();
        String md5Message = FileMd5.getMD5Message(new File("文件"));

        System.out.println(md5Message);

    }

    public static List startThread(int threadnum, long fileLength,File file) {
        List futureTaskList=new ArrayList<>();
        long modLength= fileLength % threadnum;
        long desLength = fileLength / threadnum;
        for (int i = 0; i < threadnum; i++) {
            FileMd5Message fileMd5Message = new FileMd5Message((desLength * i), (desLength * (i + 1)), file);
            System.out.println(fileMd5Message.toString());
            FutureTask futureTask = new FutureTask(fileMd5Message);
            futureTaskList.add(futureTask);
            Thread thread = new Thread(futureTask);
            thread.setName("线程"+i);
            thread.start();
        }
        if (modLength != 0) {

            FileMd5Message fileMd5Message = new FileMd5Message((desLength * threadnum), desLength * threadnum + modLength + 1, file);
            System.out.println(fileMd5Message.toString());
            FutureTask futureTask = new FutureTask(fileMd5Message);
            futureTaskList.add(futureTask);
            Thread thread = new Thread(futureTask);
            thread.setName("最后一个线程");
            thread.start();
        }

        return futureTaskList;





    }

    static class FileMd5Message implements Callable {

        //        开始位置
        private long begin;
        //        结束位置
        private long end;

        @Override
        public String toString() {
            return "FileMd5Message{" +
                    "begin=" + begin +
                    ", end=" + end +
                    ", file=" + file +
                    
                    '}';
        }

        private File file ;


        private FileInputStream fileInputStream;
        private BufferedInputStream bufferedInputStream;



        public FileMd5Message(long begin, long end, File file) {
            this.begin = begin;
            this.end = end;
            this.file = file;
            try {
                fileInputStream = new FileInputStream(file);
                bufferedInputStream=new BufferedInputStream(fileInputStream,50*1024);



            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }

        }




        @Override
        public Object call() throws Exception {



                 bufferedInputStream.skip(begin);

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

             
                byte[] buffer = new byte[Math.toIntExact(end - begin)];

                int numRead = 0;


                while (begin < end && -1 != (numRead = bufferedInputStream.read(buffer))){
                    begin += numRead;
                    messagedigest.update(buffer, 0, numRead);


                }



            String s= FileMd5Util.bufferToHex(messagedigest.digest());

            fileInputStream.close();
            bufferedInputStream.close();
            return  s;

        }




    }
}

FileMd5Util工具类

package utils;


import java.io.*;
import java.nio.ByteBuffer;
import java.security.MessageDigest;

public class FileMd5Util {
    
    protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6',
            '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

    protected static MessageDigest messagedigest = null;
    static {
        try {
            messagedigest = MessageDigest.getInstance("MD5");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    
    public static String getMD5String(String s) {
        return getMD5String(s.getBytes());
    }

    
    public static boolean checkPassword(String md5, String md5PwdStr) {
        return md5.equals(md5PwdStr);
    }

    
    public static String getFileMD5String(File file) throws IOException {
        InputStream fis;
        fis = new FileInputStream(file);
        byte[] buffer = new byte[1024];
        int numRead = 0;
        while ((numRead = fis.read(buffer)) > 0) {
            messagedigest.update(buffer, 0, numRead);
        }
        fis.close();
        return bufferToHex(messagedigest.digest());
    }

    public static String getMD5String(byte[] bytes) {
        messagedigest.update(bytes);
        return bufferToHex(messagedigest.digest());
    }

    static String bufferToHex(byte bytes[]) {
        return bufferToHex(bytes, 0, bytes.length);
    }

    private static String bufferToHex(byte bytes[], int m, int n) {
        StringBuffer stringbuffer = new StringBuffer(2 * n);
        int k = m + n;
        for (int l = m; l < k; l++) {
            appendHexPair(bytes[l], stringbuffer);
        }
        return stringbuffer.toString();
    }

    private static void appendHexPair(byte bt, StringBuffer stringbuffer) {
        char c0 = hexDigits[(bt & 0xf0) >> 4];// 取字节中高 4 位的数字转换, >>> 为逻辑右移，将符号位一起右移,此处未发现两种符号有何不同
        char c1 = hexDigits[bt & 0xf];// 取字节中低 4 位的数字转换
        stringbuffer.append(c0);
        stringbuffer.append(c1);
    }

    public static String getMD5String(InputStream inputStream) throws IOException {
        BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream,256*1024);
        ByteBuffer byteBuffer = ByteBuffer.allocate(256 * 1024);
        byte[] buffer = new byte[256*1024];

        int numRead = 0;
        while ((numRead = inputStream.read(buffer)) > 0) {
            messagedigest.update(buffer, 0, numRead);
        }
        bufferedInputStream.close();
        inputStream.close();
        return bufferToHex(messagedigest.digest());
    }


}