public class ThreadPoolClient { public static void main(String[] args) { // test1(); // test2(); // test3(); // test4(); } /** * SingleThreadExecutor:只有一个核心线程,确保所有任务都在一个线程中按顺序执行 * 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 * 核心线程数是指定的,非核心线程数不定,非核心线程数一空闲就会被回收 * 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 * 只有非核心线程,线程数可以无限大,当线程池中的线程都处于活动状态时,线程池会创建新的线程来处理任务, * 否则会利用空闲线程来处理任务,线程都有超时机制,超过60秒的闲置线程会被回收 * 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,只有核心线程且核心线程不会被回收 * 当所有线程处于活动状态时,新任务会等待状态,知道线程池有空闲线程 * 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 控制台打印,可见线程池中创建了3个线程
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 控制台打印,可见线程池中创建了5个线程
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 控制台打印,创建了2个线程
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 控制台打印 ,线程池中创建了1个线程
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