1.轮询	// 执行线程		for (Thread t : threadlist) {			t.start();		}		rewhile:while (true) {			try {				Thread.sleep(1L);			} catch (InterruptedException e) {				e.printStackTrace();			}			for (Thread t : threadlist) {				if (t.isAlive())					continue rewhile;			}						threadlist.clear();			threadlist = null;			return;		}2.连接线程        List
    
      joinReturnDigestList = new ArrayList
     
      (                fileList.size());        for (File file : fileList) {            JoinReturnDigest joinReturnDigest = new JoinReturnDigest(file);            joinReturnDigestList.add(joinReturnDigest);            joinReturnDigest.start();        }                StringBuffer result_buffer = new StringBuffer();                for(JoinReturnDigest joinReturnDigest : joinReturnDigestList){            try {                //连接线程      join       等待该线程终止                joinReturnDigest.join();                result_buffer.append(joinReturnDigest.getDigest());            } catch (InterruptedException e) {                e.printStackTrace();            }        }3.回调Class Thread:        @Override    public void run() {        FileInputStream fileInputStream;        try {            fileInputStream = new FileInputStream(file);            MessageDigest messageDigest = MessageDigest.getInstance("SHA");            DigestInputStream digestInputStream = new DigestInputStream(fileInputStream, messageDigest);            while(digestInputStream.read() != -1){}            byte[] bytes = messageDigest.digest();            this.sendDigest(bytes);        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (NoSuchAlgorithmException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    } Class CallBack:    public void calculateDigest() {        ListCallbackDigest listCallbackDigest = new ListCallbackDigest(file);        listCallbackDigest.addDigestListener(this);        Thread thread = new Thread(listCallbackDigest);        thread.start();    }    @Override    public void digestCalculated(byte[] digest) {        this.digest = digest;        System.out.println(this);    }