使用多线程统计某文件夹下，所有包含关键字的文件数量。

每个文件夹新启一个线程统计，需要返回线程的结果。

package com.learn.corejava.threading;import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;public class FutureMain {public static void main(String[] args) {String path = "E:\\cspp";String keyword = "python";MatchCounter matchCounter = new MatchCounter(new File(path), keyword);FutureTask<Integer> task = new FutureTask(matchCounter);new Thread(task).start();try {int count = task.get();System.out.println(count + " matching files.");} catch (InterruptedException e) {e.printStackTrace();} catch (ExecutionException e) {e.printStackTrace();}}
}class MatchCounter implements Callable<Integer> {private File directory;private String keyword;public MatchCounter(File directory, String keyword) {this.directory = directory;this.keyword = keyword;}@Overridepublic Integer call() throws Exception {int count = 0;File[] files = directory.listFiles();List<Future<Integer>> futures = new ArrayList<>();for (File file : files) {if (file.isDirectory()) {MatchCounter matchCounter = new MatchCounter(file, keyword);FutureTask<Integer> task = new FutureTask<>(matchCounter);futures.add(task);new Thread(task).start();} else {if (search(file)) {count++;}}}for (Future<Integer> futureTask : futures) {count += futureTask.get();}return count;}public boolean search(File file) {try(Scanner in = new Scanner(file, "utf-8")) {boolean found = false;while (!found && in.hasNextLine()) {String line = in.nextLine();if (line.contains(keyword)) {found = true;}}return found;} catch (FileNotFoundException e) {e.printStackTrace();}return false;}
}

原文地址： https://www.zhblog.net/go/java/tutorial/java8-future-task?t=590