多线程篇六：线程池

Posted 2020-08-17 陈小兵

1.固定大小的线程池
ExecutorService threadPools1=Executors.newFixedThreadPool(3);

for(int i=1;i<=10;i++){
final int task=i;
//循环10次，一共往线程池里面放10个任务
threadPools1.execute(new Runnable() {
@Override
public void run() {
System.out.println(Thread.currentThread().getName()+" loop of "+task);
}
});
}
System.out.println("The task is executd completed.....");

// 1.使用固定线程池threadPools1：
// 输出结果： 10任务每次同时有3个线程进行处理，每个线程处理一个。直到处理完10个任务
The task is executd completed.....
pool-1-thread-2 loop of 2
pool-1-thread-1 loop of 1
pool-1-thread-3 loop of 3
pool-1-thread-1 loop of 4
pool-1-thread-2 loop of 5
pool-1-thread-3 loop of 6
pool-1-thread-1 loop of 7
pool-1-thread-3 loop of 9
pool-1-thread-2 loop of 8
pool-1-thread-1 loop of 10

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2.缓存线程池（池内没有固定的线程数，根据任务的多少而创建多少个线程）
ExecutorService threadPools2=Executors.newCachedThreadPool();

for(int i=1;i<=10;i++){
            final int task=i;
            //循环10次，一共往线程池里面放10个任务
            threadPools2.execute(new Runnable() {
                @Override
                public void run() {
                    System.out.println(Thread.currentThread().getName()+" loop of "+task);
                }
            });
        }
        System.out.println("The task is executd completed.....");

        
       /* 
        * 2.使用缓存线程池threadPools2：
        * 输出结果：（线程池内直接创建10个线程，分别处理10个任务 ）
        The task is executd completed.....
        pool-2-thread-10 loop of 10
        pool-2-thread-9 loop of 9
        pool-2-thread-8 loop of 8
        pool-2-thread-7 loop of 7
        pool-2-thread-6 loop of 6
        pool-2-thread-5 loop of 5
        pool-2-thread-4 loop of 4
        pool-2-thread-3 loop of 3
        pool-2-thread-1 loop of 1
        pool-2-thread-2 loop of 2
        */

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3.单线程的线程池（池内固定有一个线程，当前线程死后会自动再创建一个，始终维持1一个线程）--比如实现案例：如何实现线程死后重新启动
ExecutorService threadPools3=Executors.newSingleThreadExecutor();

for(int i=1;i<=10;i++){
            final int task=i;
            //循环10次，一共往线程池里面放10个任务
            threadPools3.execute(new Runnable() {
                @Override
                public void run() {
                    System.out.println(Thread.currentThread().getName()+" loop of "+task);
                }
            });
        }
        System.out.println("The task is executd completed.....");
        
       /* 
        * 3.使用单一线程池 threadPools3
        * 输出结果：（由单一线程逐一处理10个任务 ）
        The task is executd completed.....
        pool-3-thread-1 loop of 1
        pool-3-thread-1 loop of 2
        pool-3-thread-1 loop of 3
        pool-3-thread-1 loop of 4
        pool-3-thread-1 loop of 5
        pool-3-thread-1 loop of 6
        pool-3-thread-1 loop of 7
        pool-3-thread-1 loop of 8
        pool-3-thread-1 loop of 9
        pool-3-thread-1 loop of 10
        */

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4.关闭线程池

//等池内的任务执行完，销毁掉线程池.
threadPools3.shutdown();

//立即销毁掉线程池.不会等待任务是否完成
threadPools3.shutdownNow();

 

5.调度线程池(定时器的线程池）

ScheduledExecutorService scheduleThreadPools=Executors.newScheduledThreadPool(3);

//10s之后执行
scheduleThreadPools.schedule(new Runnable() {
@Override
public void run() {
System.out.println("bombing!");
}
}, 10, TimeUnit.SECONDS);

//固定频率的执行 10s之后执行,每个2S执行一次
scheduleThreadPools.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
System.out.println("bombing!");
}
}, 10, 2,TimeUnit.SECONDS);