java并发编程--07（JUC组件扩展）

1.Callable与Future

    Callable与Runnable类似，只不过有返回值。

      

    Future保存异步计算的结果，

      

      Callable与Future的使用

public class Test8 {

    static class MyCallable implements Callable<String> {
        @Override
        public String call() throws Exception {
            System.out.println("doSomething in callable");
            Thread.sleep(5000);
            return "callable";
        }
    }

    public static void main(String[] args) throws Exception{
        ExecutorService executorService = Executors.newCachedThreadPool();
        Future<String> submit = executorService.submit(new MyCallable());
        System.out.println("doSomeThing in main");
        System.out.println(submit.get());

    }
}

  

2.FutureTask

    可以获得线程的返回结果

     

     ok,可以看到FutureTask是整合了Future接口的，那么FutureTask是比Future方便的，定义了这个任务，然后交给线程去处理，然后就可以遗忘它，想用的时候再用就可以了。

public class Test9 {
    public static void main(String[] args) throws Exception {
        FutureTask<String> stringFutureTask = new FutureTask<>(new Callable<String>() {
            @Override
            public String call() throws Exception {
                System.out.println("doSomething in callable");
                Thread.sleep(5000);
                return "callable";
            }
        });

        new Thread(stringFutureTask).start();
        System.out.println("doSomeThing in main");
        Thread.sleep(1000);
        String s = stringFutureTask.get();
        System.out.println(s);

    }

}

 3.Fork/Join框架

  思想类似于Mapreduce,大任务切分成小任务

  

 例子：

扫描二维码关注公众号，回复： 10102930 查看本文章

@Slf4j
public class ForkJoinTaskExample extends RecursiveTask<Integer> {

    public static final int threshold = 2;
    private int start;
    private int end;

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

    @Override
    protected Integer compute() {
        int sum = 0;

        //如果任务足够小就计算任务
        boolean canCompute = (end - start) <= threshold;
        if (canCompute) {
            for (int i = start; i <= end; i++) {
                sum += i;
            }
        } else {
            // 如果任务大于阈值，就分裂成两个子任务计算
            int middle = (start + end) / 2;
            ForkJoinTaskExample leftTask = new ForkJoinTaskExample(start, middle);
            ForkJoinTaskExample rightTask = new ForkJoinTaskExample(middle + 1, end);

            // 执行子任务
            leftTask.fork();
            rightTask.fork();

            // 等待任务执行结束合并其结果
            int leftResult = leftTask.join();
            int rightResult = rightTask.join();

            // 合并子任务
            sum = leftResult + rightResult;
        }
        return sum;
    }

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

        //生成一个计算任务，计算1+2+3+4
        ForkJoinTaskExample task = new ForkJoinTaskExample(1, 100);

        //执行一个任务
        Future<Integer> result = forkjoinPool.submit(task);

        try {
            log.info("result:{}", result.get());
        } catch (Exception e) {
            log.error("exception", e);
        }
    }
}

  4.BlockingQueue

对满队列进行入操作或者对空队列进行出操作将阻塞

 BlockingQueue的实现类：