1. @Slf4j(topic = "e")
    2. public class ForkJoinTest2 extends RecursiveTask<Long> {
    5.     private Long start;  // 1
    6.     private Long end;    // 1990900000
    8.     // 临界值
    9.     private Long temp = 10000L;
    11.     public ForkJoinTest2(Long start, Long end) {
    12.         this.start = start;
    13.         this.end = end;
    14.     }
    16.     // 计算方法
    17.     @Override
    18.     protected Long compute() {
    19.         ReentrantLock lock = new ReentrantLock();
    20.         //tiao
    21.         Condition condition = lock.newCondition();
    22.         lock.newCondition();
    24.         if ((end-start)<temp){
    25.             Long sum = 0L;
    26.             for (Long i = start; i <= end; i++) {
    27.                 sum += i;
    28.             }
    29.             return sum;
    30.         }else { // forkjoin 递归
    31.             long middle = (start + end) / 2; // 中间值
    32.             ForkJoinTest2 task1 = new ForkJoinTest2(start, middle);
    33.             task1.fork(); // 拆分任务，把任务压入线程队列
    35.             ForkJoinTest2 task2 = new ForkJoinTest2(middle+1, end);
    36.             task2.fork(); // 拆分任务，把任务压入线程队列
    37.             return task1.join() + task2.join();
    38.         }
    39.     }
    42.     public static void main(String[] args) throws ExecutionException, InterruptedException {
    43.        //6596
    44.       // test1();
    46.        //4872
    47.       // test2();
    48.         //160
    49.         test3();
    50.     }
    53.     /**
    54.      * 单线程的直接10亿累加
    55.      */
    56.     public static void test1(){
    57.         Long sum = 0L;
    58.         long start = System.currentTimeMillis();
    59.         for (Long i = 1L; i <= 10_0000_0000; i++) {
    60.             sum += i;
    61.         }
    62.         long end = System.currentTimeMillis();
    63.         System.out.println("sum="+sum+" 时间："+(end-start));
    64.     }
    67.     //最基本的forkjoin 二分查找拆分任务
    68.     //拆分任务 关键在于算法 你自己写
    70.     public static void test2(){
    72.         long start = System.currentTimeMillis();
    74.         ForkJoinPool forkJoinPool = new ForkJoinPool();
    75.         ForkJoinTask<Long> task = new ForkJoinTest2(0L, 10_0000_0000L);
    76.         Long sum = forkJoinPool.invoke(task);
    77. //        ForkJoinTask<Long> submit = forkJoinPool.submit(task);// 提交任务
    78. //        Long sum = submit.get();
    80.         long end = System.currentTimeMillis();
    82.         System.out.println("sum="+sum+" 时间："+(end-start));
    84.     }
    86.     public static void test3(){
    87.         long start = System.currentTimeMillis();
    88.         //jdk8 stream流式计算
    89.         long sum = LongStream.rangeClosed(0L, 10_0000_0000L).parallel().reduce(0, Long::sum);
    90.         long end = System.currentTimeMillis();
    91.         System.out.println("sum="+sum+"时间："+(end-start));
    92.     }
    94. }