使用多线程（线程池ThreadPoolExecutor读取多个文件、计算多个文件总行数）小demo

包括 ThreadPoolExecutor、CountDownLatch、Callable、RandomAccessFile、Nio

1.用多线程读取多个文件。

2.用多线程获取多个文件的行数后，计算几个文件的总行数。

import java.io.File; import java.io.IOException; import java.io.RandomAccessFile; import java.nio.file.Files; import java.nio.file.Paths; import java.util.concurrent.*;  public class Test {       public static void main(String[] args) throws Exception {         long startTime = System.currentTimeMillis();          final int thNum = 4;         final String[] filePath = {                 "D:\\zax\\1.txt",                 "D:\\zax\\2.txt",                 "D:\\zax\\1.txt",                 "D:\\zax\\2.txt",         };           CountDownLatch doneSignal = new CountDownLatch(thNum);          ThreadPoolExecutor executor = new ThreadPoolExecutor(                 4,                 4,                 200,                 TimeUnit.MILLISECONDS,                 new ArrayBlockingQueue<>(4)         );          // 存放总行数         long res = 0;          for (int i = 0; i < 4; i  ) {              var rf = new ReadFileThread1(doneSignal, filePath[i]);             var rf2 = new ReadFileThread2(doneSignal, filePath[i]);              // 获取并 计算总行数             Future submit = executor.submit(rf);             res  = submit.get();              // 批量读取             executor.execute(rf2);             // Future submit1 = executor.submit(rf2);         }          System.out.println(res);          try {             doneSignal.await();         } catch (InterruptedException e) {             e.printStackTrace();         } finally {             executor.shutdown();         }          long endTime = System.currentTimeMillis();         System.out.println("The totally executed time: "   (endTime - startTime));     }  }  /**  * 多线程读取多个文件，获得总行数  */  class ReadFileThread1 implements Callable {      private CountDownLatch doneSignal;     private String path;       public ReadFileThread1(CountDownLatch doneSignal, String path){         this.doneSignal = doneSignal;         this.path = path;     }     @Override     public Long call() throws Exception {         long count = Files.lines(Paths.get(new File(path).getPath())).count();         doneSignal.countDown();         return count;     } }  /**  * 多线程读取多个文件  */ class ReadFileThread2 extends Thread{     private RandomAccessFile raf;     private CountDownLatch doneSignal;     private final int bufLen = 256;     private String path;      public ReadFileThread2(CountDownLatch doneSignal, String path){         this.doneSignal = doneSignal;         this.path = path;     }       @Override     public void run() {         long start = System.currentTimeMillis();         try {             raf = new RandomAccessFile(path, "rw");             raf.seek(0);             long contentLen = new File(path).length();             long times = contentLen / bufLen  1;             byte[] buff = new byte[bufLen];             int hasRead = 0;             String result = null;             for (int i=0; i < times; i  ) {                 hasRead = raf.read(buff);                 if(hasRead < 0){                     break;                 }                 result = new String(buff, "gb2312");             }             System.out.println(Thread.currentThread()  " result = "   result);             doneSignal.countDown();         } catch (IOException e) {             e.printStackTrace();         }         long end = System.currentTimeMillis();         System.out.println(getName()   " "   path  " total Time: "   (end - start));     } }