线程池（1）——线程池的使用

public class ThreadTest {

    public static void main(String[] args) {
        /* 核心线程池的大小 */
        int corePoolSize = 2;
        /* 核心线程池的最大线程数 */
        int maxPoolSize = 4;
        /* 线程最大空闲时间 */
        long keepAliveTime = 10;
        /* 时间单位 */
        TimeUnit unit = TimeUnit.SECONDS;
        /* 阻塞队列 容量为2 */
        BlockingQueue<Runnable> workQueue = new ArrayBlockingQueue<>(2);
        /* 线程创建工厂 */
        ThreadFactory threadFactory = new NameTreadFactory();
        /* 线程池拒绝策略 */
        RejectedExecutionHandler handler = new MyIgnorePolicy();
        ThreadPoolExecutor executor = null;
        try {
            /* 推荐的创建线程池的方式 */
            /* 不推荐使用现成的API创建线程池 */
            executor = new ThreadPoolExecutor(corePoolSize,
                    maxPoolSize, keepAliveTime, unit,
                    workQueue, threadFactory, handler);
            /* 预启动所有核心线程  提升效率 */
            executor.prestartAllCoreThreads();
            /* 任务数量 */
            int count = 10;
            for (int i = 1; i <= count; i++) {
                RunnableTask task = new RunnableTask(String.valueOf(i));
                executor.submit(task);
            }
        } finally {
            assert executor != null;
            executor.shutdown();
        }

    }

    /**
     * 线程工厂
     */
    static class NameTreadFactory implements ThreadFactory {
        /* 线程id */
        private final AtomicInteger threadId = new AtomicInteger(1);

        @Override
        public Thread newThread(Runnable runnable) {
            Thread t = new Thread(runnable, "线程-" + threadId.getAndIncrement());
            System.out.println(t.getName() + " 已经被创建");
            return t;
        }
    }

    /**
     * 线程池拒绝策略
     */
    public static class MyIgnorePolicy implements RejectedExecutionHandler {

        @Override
        public void rejectedExecution(Runnable runnable, ThreadPoolExecutor e) {
            doLog(runnable, e);
        }

        private void doLog(Runnable runnable, ThreadPoolExecutor e) {
            // 可做日志记录等
            System.err.println(runnable.toString() + " rejected");
        }
    }

    /**
     * 线程
     */
    static class RunnableTask implements Runnable {
        private String name;

        public RunnableTask(String name) {
            this.name = name;
        }

        @Override
        public void run() {
            try {
                System.out.println(this.toString() + " is running!");
                //让任务执行慢点
                Thread.sleep(3000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        @Override
        public String toString() {
            return "RunnableTask [name=" + name + "]";
        }
    }

}

线程-1 已经被创建
线程-2 已经被创建
线程-3 已经被创建
RunnableTask [name=1] is running!
RunnableTask [name=2] is running!
线程-4 已经被创建
RunnableTask [name=3] is running!
java.util.concurrent.FutureTask@1f32e575 rejected
java.util.concurrent.FutureTask@279f2327 rejected
java.util.concurrent.FutureTask@2ff4acd0 rejected
java.util.concurrent.FutureTask@54bedef2 rejected
RunnableTask [name=6] is running!
RunnableTask [name=4] is running!
RunnableTask [name=5] is running!

public class CallableTest {
    public static void main(String[] args) throws InterruptedException {
        ExecutorService executor = null;
        int count = 10;
        try {
            // !!! 不推荐使用Executors的静态方法创建线程池 !!!
            executor = Executors.newCachedThreadPool();
            CompletionService<String> completionService = new ExecutorCompletionService<>(executor);
            for (int i = 0; i < count; i++) {
                FactorialCalculator factorialCalculator = new FactorialCalculator(i);
                completionService.submit(factorialCalculator);
            }

            for (int i = 0; i < count; i++) {
                Future<String> result = completionService.take();
                System.out.print(result.get());
            }
        } catch (ExecutionException e) {
            e.printStackTrace();
        } finally {
            assert executor != null;
            executor.shutdown();
        }
    }
}

public class FactorialCalculator implements Callable<String> {

    private Integer number;

    public FactorialCalculator(Integer number) {
        this.number = number;
    }

    @Override
    public String call() throws Exception {
        int result = 1;

        if (number == 0 || number == 1) {
            result = 1;
        } else {
            for (int i = 2; i <= number; i++) {
                result *= i;
                TimeUnit.MICROSECONDS.sleep(200);
            }
        }
        return String.format("%s输出%d的阶乘为：%d\n",
                Thread.currentThread().getName(), number, result);
    }
}

pool-1-thread-3输出2的阶乘为：2
pool-1-thread-6输出5的阶乘为：120
pool-1-thread-5输出4的阶乘为：24
pool-1-thread-4输出3的阶乘为：6
pool-1-thread-9输出8的阶乘为：40320
pool-1-thread-7输出6的阶乘为：720
pool-1-thread-1输出0的阶乘为：1
pool-1-thread-8输出7的阶乘为：5040
pool-1-thread-2输出1的阶乘为：1
pool-1-thread-10输出9的阶乘为：362880

public class ForkJoinPoolAction {

    public static final Set<Integer> RESULT_SET = new CopyOnWriteArraySet<>();

    public static void main(String[] args) throws Exception {
        // 验证CopyOnWriteArraySet功能 —— 去重
//        validateSet(RESULT_SET);
        // 验证FolkJoinPool功能
        validateFolkJoin();
    }

    /**
     * 验证FolkJoinPool功能
     *
     * @throws InterruptedException 中断异常
     */
    private static void validateFolkJoin() throws InterruptedException {
        // 需求：简单打印1-3000的数字
        // 程序将一个大任务拆分成多个小任务
        // 并将任务交给ForkJoinPool来执行
        PrintTask task = new PrintTask(0, 3000);
        //创建线程池
        ForkJoinPool pool = new ForkJoinPool();
        //将task提交至线程池
        pool.submit(task);
        //线程阻塞，等待所有任务完成
        pool.awaitTermination(2, TimeUnit.SECONDS);

        System.out.printf("RESULT_SET的大小=%s", RESULT_SET.size());
        pool.shutdown();
    }

    /**
     * 验证CopyOnWriteArraySet功能 —— 去重
     *
     * @param resultSet 结果集
     */
    private static void validateSet(Set<Integer> resultSet) {
        resultSet.add(1);
        resultSet.add(1);
        System.out.printf("resultSet大小=%s", resultSet.size());
    }
}

public class PrintTask extends RecursiveAction {
    /**
     * 最多只能打印50个数
     */
    private static final int THRESHOLD = 50;
    private int start;
    private int end;

    @Override
    protected void compute() {
        if (end - start < THRESHOLD) {
            for (int i = start; i < end; i++) {
                ForkJoinPoolAction.RESULT_SET.add(i);
                System.out.println(Thread.currentThread().getName() 
                        + "的i值\t" + i);
            }
        } else {
            //递归切分
            int mid = (start + end) / 2;
            PrintTask leftTask = new PrintTask(start, mid);
            PrintTask rightTask = new PrintTask(mid, end);
            //并行执行两个任务
            leftTask.fork();
            rightTask.fork();
        }
    }

    public PrintTask(int start, int end) {
        this.start = start;
        this.end = end;
    }

}

ForkJoinPool-1-worker-4的i值  703
ForkJoinPool-1-worker-4的i值  704
ForkJoinPool-1-worker-5的i值  1640
ForkJoinPool-1-worker-5的i值  1641
ForkJoinPool-1-worker-1的i值  328
ForkJoinPool-1-worker-1的i值  329
ForkJoinPool-1-worker-1的i值  330
ForkJoinPool-1-worker-0的i值  515
ForkJoinPool-1-worker-0的i值  516
ForkJoinPool-1-worker-0的i值  517
ForkJoinPool-1-worker-3的i值  2203
ForkJoinPool-1-worker-3的i值  2204
ForkJoinPool-1-worker-7的i值  2953
ForkJoinPool-1-worker-7的i值  2954
ForkJoinPool-1-worker-7的i值  2955
ForkJoinPool-1-worker-7的i值  2956
ForkJoinPool-1-worker-7的i值  2957
ForkJoinPool-1-worker-7的i值  2958
ForkJoinPool-1-worker-7的i值  2959
ForkJoinPool-1-worker-7的i值  2960
ForkJoinPool-1-worker-7的i值  2961
ForkJoinPool-1-worker-7的i值  2962
ForkJoinPool-1-worker-7的i值  2963
ForkJoinPool-1-worker-7的i值  2964
ForkJoinPool-1-worker-7的i值  2965
ForkJoinPool-1-worker-7的i值  2966
ForkJoinPool-1-worker-3的i值  2205
ForkJoinPool-1-worker-6的i值  1828
ForkJoinPool-1-worker-6的i值  1829
ForkJoinPool-1-worker-6的i值  1830
ForkJoinPool-1-worker-6的i值  1831
ForkJoinPool-1-worker-3的i值  2206
ForkJoinPool-1-worker-2的i值  1453
ForkJoinPool-1-worker-2的i值  1454
ForkJoinPool-1-worker-2的i值  1455
ForkJoinPool-1-worker-0的i值  518
ForkJoinPool-1-worker-6的i值  1832
ForkJoinPool-1-worker-6的i值  1833
ForkJoinPool-1-worker-6的i值  1834
ForkJoinPool-1-worker-6的i值  1835
ForkJoinPool-1-worker-1的i值  331
ForkJoinPool-1-worker-5的i值  1642
ForkJoinPool-1-worker-4的i值  705
ForkJoinPool-1-worker-4的i值  706
ForkJoinPool-1-worker-5的i值  1643
ForkJoinPool-1-worker-5的i值  1644
ForkJoinPool-1-worker-5的i值  1645
ForkJoinPool-1-worker-5的i值  1646
ForkJoinPool-1-worker-5的i值  1647
ForkJoinPool-1-worker-5的i值  1648
ForkJoinPool-1-worker-5的i值  1649
ForkJoinPool-1-worker-5的i值  1650
ForkJoinPool-1-worker-5的i值  1651
ForkJoinPool-1-worker-5的i值  1652
ForkJoinPool-1-worker-4的i值  707
ForkJoinPool-1-worker-1的i值  332
ForkJoinPool-1-worker-6的i值  1836
ForkJoinPool-1-worker-6的i值  1837
ForkJoinPool-1-worker-0的i值  519
ForkJoinPool-1-worker-0的i值  520
ForkJoinPool-1-worker-0的i值  521
ForkJoinPool-1-worker-0的i值  522
ForkJoinPool-1-worker-0的i值  523
ForkJoinPool-1-worker-2的i值  1456
ForkJoinPool-1-worker-2的i值  1457
ForkJoinPool-1-worker-2的i值  1458
ForkJoinPool-1-worker-2的i值  1459
ForkJoinPool-1-worker-2的i值  1460
ForkJoinPool-1-worker-2的i值  1461
ForkJoinPool-1-worker-3的i值  2207
ForkJoinPool-1-worker-3的i值  2208
ForkJoinPool-1-worker-7的i值  2967
ForkJoinPool-1-worker-3的i值  2209
ForkJoinPool-1-worker-2的i值  1462
ForkJoinPool-1-worker-0的i值  524
ForkJoinPool-1-worker-6的i值  1838
ForkJoinPool-1-worker-1的i值  333
ForkJoinPool-1-worker-4的i值  708
ForkJoinPool-1-worker-5的i值  1653
ForkJoinPool-1-worker-4的i值  709
ForkJoinPool-1-worker-1的i值  334
ForkJoinPool-1-worker-6的i值  1839
ForkJoinPool-1-worker-0的i值  525
ForkJoinPool-1-worker-2的i值  1463
ForkJoinPool-1-worker-2的i值  1464
ForkJoinPool-1-worker-2的i值  1465
ForkJoinPool-1-worker-2的i值  1466
ForkJoinPool-1-worker-2的i值  1467
ForkJoinPool-1-worker-2的i值  1468
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ForkJoinPool-1-worker-2的i值  1470
ForkJoinPool-1-worker-2的i值  1471
ForkJoinPool-1-worker-2的i值  1472
ForkJoinPool-1-worker-2的i值  1473
ForkJoinPool-1-worker-2的i值  1474
ForkJoinPool-1-worker-2的i值  1475
ForkJoinPool-1-worker-2的i值  1476
ForkJoinPool-1-worker-2的i值  1477
ForkJoinPool-1-worker-2的i值  1478
ForkJoinPool-1-worker-3的i值  2210
ForkJoinPool-1-worker-7的i值  2968
ForkJoinPool-1-worker-3的i值  2211
ForkJoinPool-1-worker-2的i值  1479
ForkJoinPool-1-worker-0的i值  526
ForkJoinPool-1-worker-6的i值  1840
ForkJoinPool-1-worker-1的i值  335
ForkJoinPool-1-worker-1的i值  336
ForkJoinPool-1-worker-1的i值  337
ForkJoinPool-1-worker-1的i值  338
ForkJoinPool-1-worker-1的i值  339
ForkJoinPool-1-worker-1的i值  340
ForkJoinPool-1-worker-1的i值  341
ForkJoinPool-1-worker-1的i值  342
ForkJoinPool-1-worker-1的i值  343
ForkJoinPool-1-worker-1的i值  344
ForkJoinPool-1-worker-1的i值  345
ForkJoinPool-1-worker-1的i值  346
ForkJoinPool-1-worker-1的i值  347
ForkJoinPool-1-worker-4的i值  710
ForkJoinPool-1-worker-5的i值  1654
ForkJoinPool-1-worker-5的i值  1655
ForkJoinPool-1-worker-5的i值  1656
ForkJoinPool-1-worker-5的i值  1657
ForkJoinPool-1-worker-5的i值  1658
ForkJoinPool-1-worker-4的i值  711
ForkJoinPool-1-worker-1的i值  348
ForkJoinPool-1-worker-6的i值  1841
ForkJoinPool-1-worker-0的i值  527
ForkJoinPool-1-worker-2的i值  1480
ForkJoinPool-1-worker-3的i值  2212
ForkJoinPool-1-worker-7的i值  2969
ForkJoinPool-1-worker-3的i值  2213
ForkJoinPool-1-worker-2的i值  1481
ForkJoinPool-1-worker-0的i值  528
ForkJoinPool-1-worker-6的i值  1842
ForkJoinPool-1-worker-1的i值  349
ForkJoinPool-1-worker-4的i值  712
ForkJoinPool-1-worker-5的i值  1659
ForkJoinPool-1-worker-4的i值  713
ForkJoinPool-1-worker-1的i值  350
ForkJoinPool-1-worker-6的i值  1843
ForkJoinPool-1-worker-0的i值  529
ForkJoinPool-1-worker-2的i值  1482
ForkJoinPool-1-worker-3的i值  2214
ForkJoinPool-1-worker-7的i值  2970
ForkJoinPool-1-worker-3的i值  2215
ForkJoinPool-1-worker-2的i值  1483
ForkJoinPool-1-worker-0的i值  530
ForkJoinPool-1-worker-6的i值  1844
ForkJoinPool-1-worker-1的i值  351
ForkJoinPool-1-worker-4的i值  714
ForkJoinPool-1-worker-5的i值  1660
ForkJoinPool-1-worker-4的i值  715
ForkJoinPool-1-worker-1的i值  352
ForkJoinPool-1-worker-6的i值  1845
ForkJoinPool-1-worker-0的i值  531
ForkJoinPool-1-worker-2的i值  1484
ForkJoinPool-1-worker-3的i值  2216
ForkJoinPool-1-worker-7的i值  2971
ForkJoinPool-1-worker-3的i值  2217
ForkJoinPool-1-worker-2的i值  1485
ForkJoinPool-1-worker-0的i值  532
ForkJoinPool-1-worker-6的i值  1846
ForkJoinPool-1-worker-1的i值  353
ForkJoinPool-1-worker-4的i值  716
ForkJoinPool-1-worker-5的i值  1661
ForkJoinPool-1-worker-4的i值  717
ForkJoinPool-1-worker-1的i值  354
ForkJoinPool-1-worker-6的i值  1847
ForkJoinPool-1-worker-0的i值  533
ForkJoinPool-1-worker-2的i值  1486
ForkJoinPool-1-worker-3的i值  2218
ForkJoinPool-1-worker-7的i值  2972
ForkJoinPool-1-worker-3的i值  2219
ForkJoinPool-1-worker-2的i值  1487
ForkJoinPool-1-worker-3的i值  2220
ForkJoinPool-1-worker-0的i值  534
ForkJoinPool-1-worker-6的i值  1848
ForkJoinPool-1-worker-0的i值  535
ForkJoinPool-1-worker-1的i值  355
ForkJoinPool-1-worker-0的i值  536
ForkJoinPool-1-worker-4的i值  718
ForkJoinPool-1-worker-5的i值  1662
ForkJoinPool-1-worker-4的i值  719
ForkJoinPool-1-worker-0的i值  537
ForkJoinPool-1-worker-1的i值  356
ForkJoinPool-1-worker-0的i值  538
ForkJoinPool-1-worker-6的i值  1849
ForkJoinPool-1-worker-3的i值  2221
ForkJoinPool-1-worker-2的i值  1488
ForkJoinPool-1-worker-7的i值  2973
ForkJoinPool-1-worker-2的i值  1489
ForkJoinPool-1-worker-7的i值  2974
ForkJoinPool-1-worker-2的i值  1490
ForkJoinPool-1-worker-3的i值  2222
ForkJoinPool-1-worker-6的i值  1850
ForkJoinPool-1-worker-3的i值  2223
ForkJoinPool-1-worker-0的i值  539
ForkJoinPool-1-worker-3的i值  2224
ForkJoinPool-1-worker-1的i值  357
ForkJoinPool-1-worker-3的i值  2225
ForkJoinPool-1-worker-1的i值  358
ForkJoinPool-1-worker-4的i值  720
ForkJoinPool-1-worker-5的i值  1663
ForkJoinPool-1-worker-4的i值  721
ForkJoinPool-1-worker-5的i值  1664
ForkJoinPool-1-worker-1的i值  359
ForkJoinPool-1-worker-3的i值  2226
ForkJoinPool-1-worker-0的i值  540
ForkJoinPool-1-worker-6的i值  1851
ForkJoinPool-1-worker-2的i值  1491
ForkJoinPool-1-worker-7的i值  2975
ForkJoinPool-1-worker-2的i值  1492
ForkJoinPool-1-worker-6的i值  1852
ForkJoinPool-1-worker-0的i值  541
ForkJoinPool-1-worker-3的i值  2227
ForkJoinPool-1-worker-1的i值  360
ForkJoinPool-1-worker-5的i值  1665
ForkJoinPool-1-worker-4的i值  722
ForkJoinPool-1-worker-5的i值  1666
ForkJoinPool-1-worker-1的i值  361
ForkJoinPool-1-worker-3的i值  2228
ForkJoinPool-1-worker-0的i值  542
ForkJoinPool-1-worker-6的i值  1853
ForkJoinPool-1-worker-2的i值  1493
ForkJoinPool-1-worker-7的i值  2976
ForkJoinPool-1-worker-2的i值  1494
ForkJoinPool-1-worker-6的i值  1854
ForkJoinPool-1-worker-0的i值  543
ForkJoinPool-1-worker-3的i值  2229
ForkJoinPool-1-worker-1的i值  362
ForkJoinPool-1-worker-5的i值  1667
ForkJoinPool-1-worker-4的i值  723
ForkJoinPool-1-worker-5的i值  1668
ForkJoinPool-1-worker-1的i值  363
ForkJoinPool-1-worker-3的i值  2230
ForkJoinPool-1-worker-0的i值  544
ForkJoinPool-1-worker-6的i值  1855
ForkJoinPool-1-worker-2的i值  1495
ForkJoinPool-1-worker-7的i值  2977
ForkJoinPool-1-worker-2的i值  1496
ForkJoinPool-1-worker-6的i值  1856
ForkJoinPool-1-worker-0的i值  545
ForkJoinPool-1-worker-3的i值  2231
ForkJoinPool-1-worker-1的i值  364
ForkJoinPool-1-worker-3的i值  2232
ForkJoinPool-1-worker-1的i值  365
ForkJoinPool-1-worker-5的i值  1669
ForkJoinPool-1-worker-4的i值  724
ForkJoinPool-1-worker-5的i值  1670
ForkJoinPool-1-worker-1的i值  366
ForkJoinPool-1-worker-3的i值  2233
ForkJoinPool-1-worker-0的i值  546
ForkJoinPool-1-worker-6的i值  1857
ForkJoinPool-1-worker-2的i值  1497
ForkJoinPool-1-worker-6的i值  1858
ForkJoinPool-1-worker-7的i值  2978
ForkJoinPool-1-worker-6的i值  1859
ForkJoinPool-1-worker-2的i值  1498
ForkJoinPool-1-worker-0的i值  547
ForkJoinPool-1-worker-3的i值  2234
ForkJoinPool-1-worker-1的i值  367
ForkJoinPool-1-worker-5的i值  1671
ForkJoinPool-1-worker-4的i值  725
ForkJoinPool-1-worker-5的i值  1672
ForkJoinPool-1-worker-1的i值  368
ForkJoinPool-1-worker-3的i值  2235
ForkJoinPool-1-worker-0的i值  548
ForkJoinPool-1-worker-2的i值  1499
ForkJoinPool-1-worker-6的i值  1860
ForkJoinPool-1-worker-7的i值  2979
ForkJoinPool-1-worker-6的i值  1861
ForkJoinPool-1-worker-2的i值  1406
ForkJoinPool-1-worker-0的i值  549
ForkJoinPool-1-worker-3的i值  2236
ForkJoinPool-1-worker-3的i值  2237
ForkJoinPool-1-worker-1的i值  369
ForkJoinPool-1-worker-5的i值  1673
ForkJoinPool-1-worker-4的i值  726
ForkJoinPool-1-worker-5的i值  1674
ForkJoinPool-1-worker-1的i值  370
ForkJoinPool-1-worker-3的i值  2238
ForkJoinPool-1-worker-0的i值  550
ForkJoinPool-1-worker-2的i值  1407
ForkJoinPool-1-worker-6的i值  1862
ForkJoinPool-1-worker-7的i值  2980
ForkJoinPool-1-worker-6的i值  1863
ForkJoinPool-1-worker-2的i值  1408
ForkJoinPool-1-worker-2的i值  1409
ForkJoinPool-1-worker-0的i值  551
ForkJoinPool-1-worker-3的i值  2239
ForkJoinPool-1-worker-1的i值  371
ForkJoinPool-1-worker-5的i值  1675
ForkJoinPool-1-worker-4的i值  727
ForkJoinPool-1-worker-5的i值  1676
ForkJoinPool-1-worker-1的i值  372
ForkJoinPool-1-worker-3的i值  2240
ForkJoinPool-1-worker-0的i值  552
ForkJoinPool-1-worker-2的i值  1410
ForkJoinPool-1-worker-6的i值  1864
ForkJoinPool-1-worker-7的i值  2981
ForkJoinPool-1-worker-6的i值  1865
ForkJoinPool-1-worker-2的i值  1411
ForkJoinPool-1-worker-0的i值  553
ForkJoinPool-1-worker-3的i值  2241
ForkJoinPool-1-worker-1的i值  373
ForkJoinPool-1-worker-5的i值  1677
ForkJoinPool-1-worker-4的i值  728
ForkJoinPool-1-worker-5的i值  1678
ForkJoinPool-1-worker-1的i值  374
ForkJoinPool-1-worker-3的i值  2242
ForkJoinPool-1-worker-0的i值  554
ForkJoinPool-1-worker-2的i值  1412
ForkJoinPool-1-worker-6的i值  1866
ForkJoinPool-1-worker-7的i值  2982
ForkJoinPool-1-worker-6的i值  1867
ForkJoinPool-1-worker-2的i值  1413
ForkJoinPool-1-worker-0的i值  555
ForkJoinPool-1-worker-3的i值  2243
ForkJoinPool-1-worker-1的i值  281
ForkJoinPool-1-worker-5的i值  1679
ForkJoinPool-1-worker-4的i值  729
ForkJoinPool-1-worker-5的i值  1680
ForkJoinPool-1-worker-1的i值  282
ForkJoinPool-1-worker-3的i值  2244
ForkJoinPool-1-worker-0的i值  556
ForkJoinPool-1-worker-2的i值  1414
ForkJoinPool-1-worker-6的i值  1868
ForkJoinPool-1-worker-7的i值  2983
ForkJoinPool-1-worker-6的i值  1869
ForkJoinPool-1-worker-2的i值  1415
ForkJoinPool-1-worker-0的i值  557
ForkJoinPool-1-worker-3的i值  2245
ForkJoinPool-1-worker-1的i值  283
ForkJoinPool-1-worker-5的i值  1681
ForkJoinPool-1-worker-4的i值  730
ForkJoinPool-1-worker-5的i值  1682
ForkJoinPool-1-worker-1的i值  284
ForkJoinPool-1-worker-3的i值  2246
ForkJoinPool-1-worker-0的i值  558
ForkJoinPool-1-worker-2的i值  1416
ForkJoinPool-1-worker-6的i值  1870
ForkJoinPool-1-worker-7的i值  2984
ForkJoinPool-1-worker-6的i值  1871
ForkJoinPool-1-worker-2的i值  1417
ForkJoinPool-1-worker-0的i值  559
ForkJoinPool-1-worker-3的i值  2247
ForkJoinPool-1-worker-1的i值  285
ForkJoinPool-1-worker-5的i值  1683
ForkJoinPool-1-worker-1的i值  286
ForkJoinPool-1-worker-4的i值  731
ForkJoinPool-1-worker-1的i值  287
ForkJoinPool-1-worker-5的i值  1684
ForkJoinPool-1-worker-3的i值  2248
ForkJoinPool-1-worker-0的i值  560
ForkJoinPool-1-worker-2的i值  1418
ForkJoinPool-1-worker-6的i值  1872
ForkJoinPool-1-worker-7的i值  2985
ForkJoinPool-1-worker-6的i值  1873
ForkJoinPool-1-worker-2的i值  1419
ForkJoinPool-1-worker-0的i值  561
ForkJoinPool-1-worker-3的i值  2249
ForkJoinPool-1-worker-5的i值  1685
ForkJoinPool-1-worker-1的i值  288
ForkJoinPool-1-worker-1的i值  289
ForkJoinPool-1-worker-1的i值  290
ForkJoinPool-1-worker-1的i值  291
ForkJoinPool-1-worker-1的i值  292
ForkJoinPool-1-worker-1的i值  293
ForkJoinPool-1-worker-1的i值  294
ForkJoinPool-1-worker-4的i值  732
ForkJoinPool-1-worker-4的i值  733
ForkJoinPool-1-worker-4的i值  734
ForkJoinPool-1-worker-4的i值  735
ForkJoinPool-1-worker-4的i值  736
ForkJoinPool-1-worker-1的i值  295
ForkJoinPool-1-worker-5的i值  1686
ForkJoinPool-1-worker-5的i值  1593
ForkJoinPool-1-worker-5的i值  1594
ForkJoinPool-1-worker-3的i值  2156
ForkJoinPool-1-worker-3的i值  2157
ForkJoinPool-1-worker-3的i值  2158
ForkJoinPool-1-worker-3的i值  2159
ForkJoinPool-1-worker-0的i值  468
ForkJoinPool-1-worker-0的i值  469
ForkJoinPool-1-worker-0的i值  470
ForkJoinPool-1-worker-2的i值  1420
ForkJoinPool-1-worker-6的i值  1874
ForkJoinPool-1-worker-7的i值  2986
ForkJoinPool-1-worker-6的i值  1781
ForkJoinPool-1-worker-2的i值  1421
ForkJoinPool-1-worker-0的i值  471
ForkJoinPool-1-worker-3的i值  2160
ForkJoinPool-1-worker-0的i值  472
ForkJoinPool-1-worker-0的i值  473
ForkJoinPool-1-worker-0的i值  474
ForkJoinPool-1-worker-0的i值  475
ForkJoinPool-1-worker-0的i值  476
ForkJoinPool-1-worker-0的i值  477
ForkJoinPool-1-worker-0的i值  478
ForkJoinPool-1-worker-0的i值  479
ForkJoinPool-1-worker-0的i值  480
ForkJoinPool-1-worker-0的i值  481
ForkJoinPool-1-worker-0的i值  482
ForkJoinPool-1-worker-0的i值  483
ForkJoinPool-1-worker-0的i值  484
ForkJoinPool-1-worker-0的i值  485
ForkJoinPool-1-worker-0的i值  486
ForkJoinPool-1-worker-0的i值  487
ForkJoinPool-1-worker-0的i值  488
ForkJoinPool-1-worker-0的i值  489
ForkJoinPool-1-worker-5的i值  1595
ForkJoinPool-1-worker-5的i值  1596
ForkJoinPool-1-worker-1的i值  296
ForkJoinPool-1-worker-4的i值  737
ForkJoinPool-1-worker-1的i值  297
ForkJoinPool-1-worker-5的i值  1597
ForkJoinPool-1-worker-1的i值  298
ForkJoinPool-1-worker-0的i值  490
ForkJoinPool-1-worker-3的i值  2161
ForkJoinPool-1-worker-2的i值  1422
ForkJoinPool-1-worker-6的i值  1782
ForkJoinPool-1-worker-2的i值  1423
ForkJoinPool-1-worker-6的i值  1783
ForkJoinPool-1-worker-2的i值  1424
ForkJoinPool-1-worker-7的i值  2987
ForkJoinPool-1-worker-2的i值  1425
ForkJoinPool-1-worker-7的i值  2988
ForkJoinPool-1-worker-2的i值  1426
ForkJoinPool-1-worker-6的i值  1784
ForkJoinPool-1-worker-3的i值  2162
ForkJoinPool-1-worker-0的i值  491
ForkJoinPool-1-worker-1的i值  299
ForkJoinPool-1-worker-5的i值  1598
ForkJoinPool-1-worker-4的i值  738
ForkJoinPool-1-worker-5的i值  1599
ForkJoinPool-1-worker-4的i值  739
ForkJoinPool-1-worker-5的i值  1600
ForkJoinPool-1-worker-1的i值  300
ForkJoinPool-1-worker-0的i值  492
ForkJoinPool-1-worker-3的i值  2163
ForkJoinPool-1-worker-6的i值  1785
ForkJoinPool-1-worker-2的i值  1427
ForkJoinPool-1-worker-7的i值  2989
ForkJoinPool-1-worker-2的i值  1428
ForkJoinPool-1-worker-7的i值  2990
ForkJoinPool-1-worker-2的i值  1429
ForkJoinPool-1-worker-6的i值  1786
ForkJoinPool-1-worker-3的i值  2164
ForkJoinPool-1-worker-6的i值  1787
ForkJoinPool-1-worker-0的i值  493
ForkJoinPool-1-worker-6的i值  1788
ForkJoinPool-1-worker-1的i值  301
ForkJoinPool-1-worker-5的i值  1601
ForkJoinPool-1-worker-4的i值  740
ForkJoinPool-1-worker-6的i值  1789
ForkJoinPool-1-worker-4的i值  741
ForkJoinPool-1-worker-6的i值  1790
ForkJoinPool-1-worker-0的i值  494
ForkJoinPool-1-worker-1的i值  302
ForkJoinPool-1-worker-6的i值  1791
ForkJoinPool-1-worker-3的i值  2165
ForkJoinPool-1-worker-6的i值  1792
ForkJoinPool-1-worker-2的i值  1430
ForkJoinPool-1-worker-7的i值  2991
ForkJoinPool-1-worker-0的i值  495
ForkJoinPool-1-worker-4的i值  742
ForkJoinPool-1-worker-5的i值  1602
ForkJoinPool-1-worker-0的i值  496
ForkJoinPool-1-worker-7的i值  2992
ForkJoinPool-1-worker-5的i值  1603
ForkJoinPool-1-worker-6的i值  1793
ForkJoinPool-1-worker-4的i值  743
ForkJoinPool-1-worker-1的i值  303
ForkJoinPool-1-worker-6的i值  1794
ForkJoinPool-1-worker-3的i值  2166
ForkJoinPool-1-worker-6的i值  1795
ForkJoinPool-1-worker-4的i值  744
ForkJoinPool-1-worker-2的i值  1431
ForkJoinPool-1-worker-0的i值  497
ForkJoinPool-1-worker-2的i值  1432
ForkJoinPool-1-worker-7的i值  2993
ForkJoinPool-1-worker-5的i值  1604
ForkJoinPool-1-worker-1的i值  304
ForkJoinPool-1-worker-3的i值  2167
ForkJoinPool-1-worker-6的i值  1796
ForkJoinPool-1-worker-3的i值  2168
ForkJoinPool-1-worker-4的i值  745
ForkJoinPool-1-worker-0的i值  498
ForkJoinPool-1-worker-4的i值  746
ForkJoinPool-1-worker-0的i值  499
ForkJoinPool-1-worker-2的i值  1433
ForkJoinPool-1-worker-7的i值  2994
ForkJoinPool-1-worker-5的i值  1605
ForkJoinPool-1-worker-7的i值  2995
······
RESULT_SET的大小=3000

public class ForkJoinPoolTask {
    public static void main(String[] args) throws Exception {
        //需求：对于长度为10000的元素数组进行累加
        int[] nums = new int[10000];
        Random random = new Random();
        int total = 0;
        //初始化数组元素
        long start = System.nanoTime();
        for (int i = 0; i < nums.length; i++) {
            int temp = random.nextInt(100);
            nums[i] = temp;
            total += nums[i];
        }
        long end = System.nanoTime();
        System.out.println("初始化数组用时：" + (end - start) + "纳秒, 初始化数组总和:" + total);

        long startTask = System.nanoTime();
        //创建Task
        SumTask task = new SumTask(nums, 0, nums.length);
        //创建线程池
        ForkJoinPool pool = new ForkJoinPool();
        //提交任务,存在返回值
        ForkJoinTask<Integer> future = pool.submit(task);
        //显示结果
        long endTask = System.nanoTime();
        System.out.println("线程池计算用时：" + (endTask - startTask) + "纳秒, 线程池执行结果:" + future.get());
        //关闭多线程
        pool.shutdown();

    }
}

public class SumTask extends RecursiveTask<Integer> {
    /**
     * 每个小任务，最多只累加20个数
     */
    private static final int THRESHOLD = 20;
    private int nums[];
    private int start;
    private int end;

    public SumTask(int[] nums, int start, int end) {
        super();
        this.nums = nums;
        this.start = start;
        this.end = end;
    }

    @Override
    protected Integer compute() {
        int sum = 0;
        if (end - start < THRESHOLD) {
            for (int i = start; i < end; i++) {
                sum += nums[i];
            }
            return sum;
        } else {
            //当分块超过阈值时，则需要对数据进行拆分
            int mid = (start + end) / 2;
            SumTask leftTask = new SumTask(nums, start, mid);
            SumTask rightTask = new SumTask(nums, mid, end);
            //并行执行两个小任务
            leftTask.fork();
            rightTask.fork();
            //把两个小任务累加合并
            return leftTask.join() + rightTask.join();
        }
    }
}

初始化数组用时：1847192纳秒, 初始化数组总和:493016
线程池计算用时：4220889纳秒, 线程池执行结果:493016