java CountDownLatch 多線程文件搜索

基於多線程搜索文件，並且將最終的結果進行打印。這裏使用了CountDownLatch線程協作機制，主線程等待多個搜索線程完成，並對最終結果進行打印。另外使用了CopyOnWriteArrayList來保障多個線程保存操作結果的併發安全。具體例子如下：

package com.tuobana.concurrent.cyclibarrier;

import java.io.File;
import java.util.Date;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.CountDownLatch;

/**
 * Created by lpn on 2016/3/7.
 */
public class SearchFile {
    public static void main(String argv[]) throws InterruptedException {
        List<String> results = new CopyOnWriteArrayList<String>();
        String path = "e:/";
        String searchName = "XXXStringUtil.java";

        File file = new File(path);
        if (!file.exists() || !file.isDirectory()) {
            System.out.println("文件查找失敗：" + path + "不是一個目錄！");
        } else {
            File files[] = file.listFiles();
            if (files != null && files.length > 0) {
                CountDownLatch latch = new CountDownLatch(files.length);
                System.out.println("All thread started at " + new Date());
                for (File f : files) {
                    Thread t = new Thread(new SearchTask(f.getPath(), searchName, results, latch));
                    t.setName("Thread-" + f.getName());
                    t.start();
                }
                latch.await();
                System.out.println("All thread finished at " + new Date());
            }
        }
        System.out.println(results.toString());
    }
}


class SearchTask implements Runnable {
    private String path;
    private String fileName;
    private List<String> results;
    private CountDownLatch latch;
    public SearchTask(String path, String fileName, List<String> results, CountDownLatch latch) {
        this.path = path;
        this.fileName = fileName;
        this.results = results;
        this.latch = latch;
    }

    @Override
    public void run() {
        searchFile(this.path, this.fileName, this.results);
        latch.countDown();
    }

    private void searchFile(String path, String fileName, List<String> results) {
        File file = new File(path);
        if (!file.exists() || !file.isDirectory()){
            System.out.println("文件查找失敗：" + path + "不是一個目錄！");
        } else {
            File files[] = file.listFiles();
            if (files != null && files.length > 0) {
                for (File f : files) {
                    if (f.isDirectory()) {
                        searchFile(f.getAbsolutePath(), fileName, results);
                    } else {
                        if (f.getName().equals(fileName)) {
                            results.add(f.getAbsolutePath());
                        }
                    }
                }
            }
        }
    }
}