マルチスレッド——1から100までの加算タスクをfork/joinに分割します.

記事の目次

テーマ:マルチスレッドを使って1から100までの加算タスクを実現する

.マルチスレッドを使って解決するアプリケーションCountDownLatch

.fork/joinを使って

を完成する.
テーマ:マルチスレッドを使って、1から100までの加算タスクを実現します.
1.マルチスレッドを使って解決する——CountDownLatchを適用する

/**
 *        1-10000  
 *  CountDownLatch ：       ，                   ，              。
 *            CountDownLatch。   countDown()       1，   0  ，await         。
 *   ，          ，await              。
 *       A，      N             ,     CountDownLatch。
 **/

public class Thread_OneToN {

    private static int sum = 0;
    private static int idnex = 10000;

    //  10      
    private static int thNum = 10;
    //  CountDownLatch        
    private static CountDownLatch countDownLatch;
    private static Lock lock;

    public static void main(String[] args) throws InterruptedException {
        countDownLatch = new CountDownLatch(thNum);
        lock = new ReentrantLock();

        //           
        int avNum = idnex / thNum;

        int left, right;
        for (int i = 1; i <= thNum; i++) {
            left = (i - 1) * avNum + 1;
            right = i * avNum;
            new Thread(new CountThread(left, right)).start();
        }
        //                      
        countDownLatch.await();

        System.out.println(Thread.currentThread().getName() + " sum " + sum);

    }

    //     
    static class CountThread implements Runnable {

        private int left;
        private int right;

        public CountThread(int left, int right) {
            this.left = left;
            this.right = right;
        }

        @Override
        public void run() {
            //              res ，          sum 
            int res = 0;
            for (int i = left; i <= right; i++) {
                res += i;
            }
            try {
                //  ，  sum          
                lock.lock();
                sum += res;
                System.out.println(Thread.currentThread().getName() + " -- " + " left " + left + " right " + right + " sum " + sum);
                //              
                countDownLatch.countDown();
            } finally {
                lock.unlock();
            }
        }
    }
}

2.fork/joinを使って完成します.

import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.Future;
import java.util.concurrent.RecursiveTask;

/**
 * ForkJoin  ,   1  100  
 *
 */
public class ForkJoinTaskExample extends RecursiveTask<Integer> {

    private static final long serialVersionUID = 1L;

    public static final int threadsHold = 10;
    private int start;
    private int end;

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

	/**
      * compute    RecursiveTask        
     */
    @Override
    protected Integer compute() {
        int sum = 0;
        //            
        boolean canCompute = (end - start) <= threadsHold;
        if (canCompute) {
            for (int i = start; i <= end; i++) {
                sum += i;
            }
        } else {
            //         ，           
            int middle = (start + end) / 2;
            ForkJoinTaskExample leftTask = new ForkJoinTaskExample(start, middle);
            ForkJoinTaskExample rightTask = new ForkJoinTaskExample(middle + 1, end);

            //      
            leftTask.fork();
            rightTask.fork();

            //              
            int leftResult = leftTask.join();
            int rightResult = rightTask.join();

            //      
            sum = leftResult + rightResult;
        }
        return sum;
    }

    public static void main(String[] args) {
        ForkJoinPool forkjoinPool = new ForkJoinPool();

        //        
        ForkJoinTaskExample task = new ForkJoinTaskExample(1, 100);

        //      
        Future<Integer> result = forkjoinPool.submit(task);

        try {
            System.out.printf("result:{%s}", result.get());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}