一、主线程等待法:优点:实现简单,缺点:代码冗余
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:
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
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
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; } }
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
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(); } } }