Java多线程-处理线程的返回值
一、主线程等待法:优点:实现简单,缺点:代码冗余
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | package com.test.thread; public class CycleWait implements Runnable { private String value; @Override public void run() { try { Thread.sleep( 5000 ); } catch (InterruptedException e) { e.printStackTrace(); } value = "we have data now" ; } public static void main(String[] args) throws InterruptedException { CycleWait cycleWait = new CycleWait(); Thread t = new Thread(cycleWait); t.start(); while (cycleWait.value == null ) { Thread.sleep( 100 ); } System.out.println(cycleWait.value); } } |
运行结果:
1 | we have data now |
二、使用Thread类的join()阻塞当前线程,以等待子线程处理完毕。优点:比“主线程等待法”更简单 缺点:粒度不够细
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | package com.test.thread; public class CycleWait implements Runnable { private String value; @Override public void run() { try { Thread.sleep( 5000 ); } catch (InterruptedException e) { e.printStackTrace(); } value = "we have data now" ; } public static void main(String[] args) throws InterruptedException { CycleWait cycleWait = new CycleWait(); Thread t = new Thread(cycleWait); t.start(); // join方法,在start后 t.join(); System.out.println(cycleWait.value); } } |
三、通过Callable接口实现:通过FutureTask 或者 线程池获取
1、future task
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | MyCallable. class : package com.test.thread; import java.util.concurrent.Callable; // 实现callable接口 public class MyCallable implements Callable<String> { @Override public String call() throws Exception { String value = "test" ; System.out.println( "ready to work" ); Thread.sleep( 5000 ); System.out.println( "task done" ); return value; } } |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | FutureTaskDemo. class : package com.test.thread; import java.util.concurrent.ExecutionException; import java.util.concurrent.FutureTask; //future task public class FutureTaskDemo { 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、线程池
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | TreadPoolDemo. class : package com.test.thread; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; public class TreadPoolDemo { public static void main(String[] args) { // 创建线程池 ExecutorService executorService = Executors.newCachedThreadPool(); // 向线程池中提交任务 Future<String> future = executorService.submit( new MyCallable()); // 判断任务是否完成 if (!future.isDone()) { System.out.println( "task not finished, please wait~~" ); } try { System.out.println(future.get()); } catch (InterruptedException e) { e.printStackTrace(); } catch (ExecutionException e) { e.printStackTrace(); } finally { // 将线程池关闭 executorService.shutdown(); } } } |
分类:
Java
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