Java多线程求和

package test;

import java.util.concurrent.*; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock;

public class SumService {

private final Integer nthread;

private final ExecutorService executorService;
private final Lock lock;
private final CountDownLatch countDownLatch;
private Integer sum;
public SumService(){

    this.sum = new Integer(0);
    this.nthread = new Integer(100);
    this.executorService = new ThreadPoolExecutor(10, nthread, 10L, TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(nthread));
    this.lock = new ReentrantLock();
    this.countDownLatch = new CountDownLatch(nthread);
}

public Integer call() throws Exception{

    for (int i = 0; i < nthread; i++) {
        executorService.execute(()-> sum());
    }
    executorService.shutdown();
    countDownLatch.await();
    return sum;
}

private void sum(){
    for (int i = 0; i < 10000; i++) {
        lock.lock();
        sum++;
        lock.unlock();
    }
    countDownLatch.countDown();
}

public static void main(String[] args) throws Exception{
    SumService sumService = new SumService();
    Integer sum = sumService.call();
    System.out.println(sum);
}

} `