初見線程池

public class ThreadPoolClient {
    public static void main(String[] args) {
//        test1();
//        test2();
//        test3();
//        test4();
    }

    /**
     * SingleThreadExecutor:只有一個核心線程,確保所有任務都在一個線程中按順序執行
     * new ThreadPoolExecutor(1, 1,0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>())
     */
    private static void test4() {
        ExecutorService executorService = Executors.newSingleThreadExecutor();
        executorService.execute(new MyRun());
        executorService.execute(new MyRun());
        executorService.execute(new MyRun());
        executorService.execute(new MyRun());
        executorService.execute(new MyRun());

    }

    /**
     * ScheduledThreadPool
     * 核心線程數是指定的,非核心線程數不定,非核心線程數一空閒就會被回收
     * public class ScheduledThreadPoolExecutor extends ThreadPoolExecutor implements ScheduledExecutorService
     * new ScheduledThreadPoolExecutor(corePoolSize);
     * super(corePoolSize, Integer.MAX_VALUE,DEFAULT_KEEPALIVE_MILLIS, MILLISECONDS,new DelayedWorkQueue())
     */
    private static void test3() {
        ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(2);
        scheduledExecutorService.schedule(new MyRun(), 1000, TimeUnit.MILLISECONDS);
        scheduledExecutorService.schedule(new MyRun(), 1000, TimeUnit.MILLISECONDS);
        scheduledExecutorService.schedule(new MyRun(), 1000, TimeUnit.MILLISECONDS);
        scheduledExecutorService.schedule(new MyRun(), 1000, TimeUnit.MILLISECONDS);
        scheduledExecutorService.schedule(new MyRun(), 1000, TimeUnit.MILLISECONDS);
    }

    /**
     * CachedThreadPool
     * 只有非核心線程,線程數可以無限大,當線程池中的線程都處於活動狀態時,線程池會創建新的線程來處理任務,
     * 否則會利用空閒線程來處理任務,線程都有超時機制,超過60秒的閒置線程會被回收
     * new ThreadPoolExecutor(0, Integer.MAX_VALUE,60L, TimeUnit.SECONDS,new SynchronousQueue<Runnable>());
     */
    private static void test2() {
        ExecutorService executorService = Executors.newCachedThreadPool();
        executorService.execute(new MyRun());
        executorService.execute(new MyRun());
        executorService.execute(new MyRun());
        executorService.execute(new MyRun());
        executorService.execute(new MyRun());

    }

    /**
     * FixedThreadPool,只有核心線程且核心線程不會被回收
     * 當所有線程處於活動狀態時,新任務會等待狀態,知道線程池有空閒線程
     * new ThreadPoolExecutor(nThreads, nThreads,0L, TimeUnit.MILLISECONDS,new LinkedBlockingQueue<Runnable>());
     */
    private static void test1() {
        ExecutorService executorService = Executors.newFixedThreadPool(3);
        executorService.execute(new MyRun());
        executorService.execute(new MyRun());
        executorService.execute(new MyRun());
        executorService.execute(new MyRun());
        executorService.execute(new MyRun());
    }
}

class MyRun implements Runnable {

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getId() + "---" + Thread.currentThread().getName());
    }
}

 

test1   控制檯打印,可見線程池中創建了3個線程

13---pool-1-thread-2
14---pool-1-thread-3
13---pool-1-thread-2
12---pool-1-thread-1
14---pool-1-thread-3

 

test2 控制檯打印,可見線程池中創建了5個線程

12---pool-1-thread-1
15---pool-1-thread-4
13---pool-1-thread-2
14---pool-1-thread-3
16---pool-1-thread-5

test3  控制檯打印,創建了2個線程

13---pool-1-thread-2
12---pool-1-thread-1
13---pool-1-thread-2
12---pool-1-thread-1
13---pool-1-thread-2

test4 控制檯打印 ,線程池中創建了1個線程

12---pool-1-thread-1
12---pool-1-thread-1
12---pool-1-thread-1
12---pool-1-thread-1
12---pool-1-thread-1