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  • Java多线程和并发(四),线程返回值获取方式和Callable接口

    目录

    1.主线程等待法

    2.使用Thread类的join()阻塞当前线程,等待子线程执行完毕

    3.通过Callable接口实现:通过FutureTask Or线程池获取

    四、线程返回值获取方式和Callable接口

    1.主线程等待法

    public class CycleWait implements Runnable{
        private String value;
        @Override
        public void run() {
            try {
                Thread.currentThread().sleep(5000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            value = "we have data now";
        }
        public static void main(String[] args) throws InterruptedException {
            CycleWait cw = new CycleWait();
            Thread t = new Thread(cw);
            t.start();
            while (cw.value == null){
                Thread.currentThread().sleep(100);
            }
            System.out.println("value : " + cw.value);
        }
    }

    2.使用Thread类的join()阻塞当前线程,等待子线程执行完毕 

    public class CycleWait implements Runnable{
        private String value;
        @Override
        public void run() {
            try {
                Thread.currentThread().sleep(5000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            value = "we have data now";
        }
    
        public static void main(String[] args) throws InterruptedException {
            CycleWait cw = new CycleWait();
            Thread t = new Thread(cw);
            t.start();
            t.join();
            System.out.println("value : " + cw.value);
        }
    }

    缺点很明显,不够精准,只能等子线程结束才能继续主线程

    3.通过Callable接口实现:通过FutureTask Or线程池获取

    (1)使用FutureTask获取返回值

    public class MyCallable implements Callable<String> {
        @Override
        public String call() throws Exception{
            String value="test";
            System.out.println("Ready to work");
            Thread.currentThread().sleep(5000);
            System.out.println("task done");
            return  value;
        }
        public static void main(String[] args) throws ExecutionException, InterruptedException {
            FutureTask<String> task = new FutureTask<String>(new MyCallable());
            new Thread(task).start();
            if(!task.isDone()){
                System.out.println("task has not finished, please wait!");
            }
            System.out.println("task return: " + task.get());
        }
    }

    (2)通过线程池获取返回值

    public class MyCallable implements Callable<String> {
        @Override
        public String call() throws Exception{
            String value="test";
            System.out.println("Ready to work");
            Thread.currentThread().sleep(5000);
            System.out.println("task done");
            return  value;
        }
        public static void main(String[] args) {
            ExecutorService newCachedThreadPool = Executors.newCachedThreadPool();
            Future<String> future = newCachedThreadPool.submit(new MyCallable());
            if(!future.isDone()){
                System.out.println("task has not finished, please wait!");
            }
            try {
                System.out.println(future.get());
            } catch (Exception e) {
                e.printStackTrace();
            }finally {
                newCachedThreadPool.shutdown();
            }
        }
    }
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  • 原文地址:https://www.cnblogs.com/xzmxddx/p/10362810.html
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