Java并发学习之十九——线程同步工具之Phaser

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JDK 1.7 添加了一个新的工具Phaser，Phaser的在功能上与CountDownLatch有部分重合。

下面使用Phaser类来同步3个并发任务。这3个任务会在3个不同的文件夹和它们的子文件夹中搜索扩展名是.log的文件。这个任务被分成3个步骤：

1. 在指定的文件夹和子文件夹中获得文件扩展名为.log的文件列表。
2. 在操控台打印结果。

在步骤1和步骤2的结尾我们要检查列表是否为空。如果为空，那么线程直接结束运行并从phaser类中淘汰。

package chapter3;import java.io.File;import java.util.ArrayList;import java.util.Date;import java.util.List;import java.util.concurrent.Phaser;import java.util.concurrent.TimeUnit;public class FileSearch implements Runnable{private String initPath;private String end;private List<String> results;private Phaser phaser;public FileSearch(String initPath,String end,Phaser phaser ){this.initPath = initPath;this.end = end;this.phaser = phaser;this.results = new ArrayList<String>();}private void directoryProcess(File file){File list[] = file.listFiles();if(list != null){for(int i = 0;i< list.length;i++){if(list[i].isDirectory()){directoryProcess(list[i]);}else{fileProcess(list[i]);}}}}private void fileProcess(File file){if(file.getName().endsWith(end)){results.add(file.getAbsolutePath());}}private void filterResults(){List<String> newResults = new ArrayList<String>();long actualDate = new Date().getTime();for (int i = 0; i < results.size(); i++) {File file = new File(results.get(i));long fileDate = file.lastModified();if(actualDate-fileDate<TimeUnit.MILLISECONDS.convert(1, TimeUnit.DAYS)){newResults.add(results.get(i));}}results = newResults;}private boolean checkResults(){if(results.isEmpty()){System.out.printf("%s: Phase %d: 0 results.\n", Thread.currentThread().getName(), phaser.getPhase());System.out.printf("%s: Phase %d: End.\n", Thread.currentThread().getName(), phaser.getPhase());phaser.arriveAndDeregister();return false;}else{System.out.printf("%s: Phase %d: %d results.\n", Thread.currentThread().getName(), phaser.getPhase(), results.size());phaser.arriveAndAwaitAdvance();return true;}}private void showInfo(){for (int i = 0; i < results.size(); i++) {File file = new File(results.get(i));System.out.printf("%s: %s\n", Thread.currentThread().getName(),file.getAbsolutePath());}phaser.arriveAndAwaitAdvance();}@Overridepublic void run() {phaser.arriveAndAwaitAdvance();System.out.printf("%s: Starting.\n", Thread.currentThread().getName());File file = new File(initPath);if(file.isDirectory()){directoryProcess(file);}if(!checkResults()){return ;}filterResults();if(!checkResults()){return;}showInfo();phaser.arriveAndDeregister();System.out.printf("%s: Work completed.\n", Thread.currentThread().getName());}}

package chapter3;import java.util.concurrent.Phaser;public class Main5 {/** * <p> * </p> * @author zhangjunshuai * @date 2014-9-29 下午4:31:46 * @param args */public static void main(String[] args) {Phaser phaser = new Phaser(3);FileSearch system = new FileSearch("C:\\Windows","log",phaser);FileSearch apps = new FileSearch("c:\\Program Files","log",phaser);FileSearch documents = new FileSearch("c:\\Documents And Settings","log",phaser);Thread systemThread = new Thread(system,"System");systemThread.start();Thread appsThread = new Thread(apps,"apps");appsThread.start();Thread documentsThread = new Thread(documents,"documents");documentsThread.start();try {systemThread.join();appsThread.join();documentsThread.join();} catch (Exception e) {e.printStackTrace();}System.out.println("Terminated: " + phaser.isTerminated());}}

运行结果

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