CountDownLatch的API讲解

1.使用executor.awaitTermination(1, TimeUnit.HOURS);

package com.dwz.utils;

import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public class CountDownLatchExample1 {
    private static Random random = new Random(System.currentTimeMillis());
    private static ExecutorService executor = Executors.newFixedThreadPool(2);
    private static final CountDownLatch countDownLatch = new CountDownLatch(11);
    
    public static void main(String[] args) throws InterruptedException {
        //(1)查询数据
        int[] data = query();
        //(2)并行处理数据
        for(int i = 0; i < data.length; i++) {
            executor.execute(new SimpleRunnable(data, i));
        }
        //(3)
        executor.shutdown();
        executor.awaitTermination(1, TimeUnit.HOURS);
        System.out.println("all of work finish done.");
    }
    
    static class SimpleRunnable implements Runnable    {
        private final int[] data;
        private final int index;
        
        public SimpleRunnable(int[] data, int index) {
            this.data = data;
            this.index = index;
        }
        
        @Override
        public void run() {
            try {
                Thread.sleep(random.nextInt(2000));
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            
            int value = data[index];
            if(value % 2 == 0) {
                data[index] = value * 2;
            } else {
                data[index] = value * 10;
            }
            System.out.println(Thread.currentThread().getName() + " finished.");
        }
    }
    
    private static int[] query() {
        return new int[] {0,1,2,3,4,5,6,7,8,9,10};
    }
}

2.使用countDownLatch.await();

package com.dwz.utils;

import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public class CountDownLatchExample1 {
    private static Random random = new Random(System.currentTimeMillis());
    private static ExecutorService executor = Executors.newFixedThreadPool(2);
    private static final CountDownLatch countDownLatch = new CountDownLatch(11);
    
    public static void main(String[] args) throws InterruptedException {
        //(1)查询数据
        int[] data = query();
        //(2)并行处理数据
        for(int i = 0; i < data.length; i++) {
            executor.execute(new SimpleRunnable(data, i));
        }
        //(3)
        countDownLatch.await();
        System.out.println("all of work finish done.");
    }
    
    static class SimpleRunnable implements Runnable    {
        private final int[] data;
        private final int index;
        
        public SimpleRunnable(int[] data, int index) {
            this.data = data;
            this.index = index;
        }
        
        @Override
        public void run() {
            try {
                Thread.sleep(random.nextInt(2000));
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            
            int value = data[index];
            if(value % 2 == 0) {
                data[index] = value * 2;
            } else {
                data[index] = value * 10;
            }
            countDownLatch.countDown();
            System.out.println(Thread.currentThread().getName() + " finished.");
        }
    }
    
    private static int[] query() {
        return new int[] {0,1,2,3,4,5,6,7,8,9,10};
    }
}

3.latch.await();和latch.countDown();的混合使用

package com.dwz.utils;

import java.util.concurrent.CountDownLatch;

public class CountDownLatchExample2 {
    public static void main(String[] args) {
        final CountDownLatch latch = new CountDownLatch(1);
        
        new Thread() {
            @Override
            public void run() {
                System.out.println("Do some initial work.");
                try {
                    Thread.sleep(1000);
                    latch.await();
                    System.out.println("Do other work.");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }.start();
        
        new Thread() {
            @Override
            public void run() {
                System.out.println("asyn prepare for some data.");
                try {
                    Thread.sleep(2000);
                    System.out.println("data prepare done.");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } finally {
                    latch.countDown();
                }
            }
        }.start();
    }
}