# Thread Pool ## CachedThreadPool * 默认 最大 `Interger. MAX_VALUE` 线程数的线程池 * `ExecutorService service = Executors.newCachedThreadPool()` ## FixedThreadPool * 定长线程池，最优数量：`Runtime.getRuntime().availableProcessors()` * 不会释放线程 * `ExecutorService service Executors.newFixedThreadPool(10);` ## SingleThreadPool * 同时只有一个线程运行，可以按照指定顺序\(FIFO, LIFO, 优先级\)执行 * `ExecutorService service = Executors.newSingleThreadExecutor();` ## ScheduleThreadPool * 定时执行线程池 * `ExecutorService service = Executors.newScheduledThreadPool(10);` ## WorkStealingPool * Fork/Join ```java public static void main(String[] args) throws IOException { // 根据cpu是几核来开启几个线程 ExecutorService service = Executors.newWorkStealingPool(); // 查看当前计算机是几核 System.out.println(Runtime.getRuntime().availableProcessors()); service.execute(new R(1000)); service.execute(new R(2000)); service.execute(new R(3000)); service.execute(new R(1000)); service.execute(new R(2000)); // WorkStealing是精灵线程(守护线程、后台线程)，主线程不阻塞，看不到输出。 // 虚拟机不停止，守护线程不停止 System.in.read(); } static class R implements Runnable { int time; public R(int time) { this.time = time; } @Override public void run() { try { TimeUnit.MILLISECONDS.sleep(time); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(time + ":" + Thread.currentThread().getName()); } } 1000:ForkJoinPool-1-worker-1 1000:ForkJoinPool-1-worker-4 2000:ForkJoinPool-1-worker-2 2000:ForkJoinPool-1-worker-5 3000:ForkJoinPool-1-worker-3 ```