Android（Java）线程池：ExecutorService和Executors使用（二）

一、固定大小的线程池，newFixedThreadPool：

package Executor.test;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ExecutorTest {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        doExecutor();
    }

    static void doExecutor()
    {
        //create reuse,fix number,thread pool
        ExecutorService pool = Executors.newFixedThreadPool(5);
        //create threads
        Thread t1 = new Thread(new MyThread());
        Thread t2 = new Thread(new MyThread());
        Thread t3 = new Thread(new MyThread());
        Thread t4 = new Thread(new MyThread());
        Thread t5 = new Thread(new MyThread());
        //execute thread in thread pool
        pool.execute(t1);
        pool.execute(t2);
        pool.execute(t3);
        pool.execute(t4);
        pool.execute(t5);
        //shutdown thread pool
        pool.shutdown();
    }
    
    static class MyThread implements Runnable
    {
        @Override
        public void run() {
            // TODO Auto-generated method stub
            System.out.println("running thread:"+Thread.currentThread().getName());
        }
    }
}

执行结果：

running thread:pool-1-thread-1
running thread:pool-1-thread-3
running thread:pool-1-thread-5
running thread:pool-1-thread-2
running thread:pool-1-thread-4

改变线程池的大小：

ExecutorService pool = Executors.newFixedThreadPool(3)

执行结果：

running thread:pool-1-thread-1
running thread:pool-1-thread-1
running thread:pool-1-thread-1
running thread:pool-1-thread-2
running thread:pool-1-thread-3

结论：从以上结果可以看出，newFixedThreadPool的参数指定了可以运行的线程的最大数目，超过这个数目的线程加进去以后，不会运行。其次，加入线程池的线程属于托管状态，线程的运行不受加入顺序的影响。

 二、单任务线程池，newSingleThreadExecutor：

ExecutorService pool = Executors.newSingleThreadExecutor();

result:

running thread:pool-1-thread-1
running thread:pool-1-thread-1
running thread:pool-1-thread-1
running thread:pool-1-thread-1
running thread:pool-1-thread-1

结论：每次调用execute方法，其实最后都是调用了thread-1的run方法。

三、可变尺寸的线程池，newCachedThreadPool：

ExecutorService pool = Executors.newCachedThreadPool();

result:

running thread:pool-1-thread-1
running thread:pool-1-thread-2
running thread:pool-1-thread-3
running thread:pool-1-thread-4
running thread:pool-1-thread-5

结论：可根据需要创建新线程的线程池，但是在以前构造的线程可用时将重用它们。

四、延迟连接池，newScheduledThreadPool：

package Executor.test;

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class ExecutorTest {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        doExecutor();
    }

    static void doExecutor()
    {
        //create scheduled thread pool
        ScheduledExecutorService pool = Executors.newScheduledThreadPool(3);
        //create threads
        Thread t1 = new Thread(new MyThread());
        Thread t2 = new Thread(new MyThread());
        Thread t3 = new Thread(new MyThread());
        Thread t4 = new Thread(new MyThread());
        Thread t5 = new Thread(new MyThread());
        //execute thread in thread pool
        pool.execute(t1);
        pool.execute(t2);
        //schedule method
        pool.schedule(t3, 1000, TimeUnit.MILLISECONDS);
        pool.schedule(t4, 2000, TimeUnit.MILLISECONDS);
        pool.schedule(t5, 3000, TimeUnit.MILLISECONDS);
        //shutdown thread pool
        pool.shutdown();
    }
    
    static class MyThread implements Runnable
    {
        @Override
        public void run() {
            // TODO Auto-generated method stub
            System.out.println("running thread:"+Thread.currentThread().getName());
        }
    }
}

result:

running thread:pool-1-thread-1
running thread:pool-1-thread-2
running thread:pool-1-thread-3
running thread:pool-1-thread-1
running thread:pool-1-thread-2

结论：运行结果可以看到，后面三条依次间隔一秒执行，起到定时周期执行任务的作用

参考：Android的ExecutorService线程池 | 学步园