Java 异步转同步方案：使用 CountDownLatch、使用 CyclicBarrier、使用 wait/notify + synchronized

Java 异步转同步方案

准备阶段

• Student.java

publicclassStudent{publicvoidstudy(StudentStudyObserverstudentStudyObserver){newThread(()->{try{TimeUnit.SECONDS.sleep(5);}catch(InterruptedExceptione){e.printStackTrace();}studentStudyObserver.onFinish();}).start();}}

• StudentStudyObserver.java

publicinterfaceStudentStudyObserver{voidonFinish();}

1、使用 CountDownLatch

CountDownLatchcountDownLatch=newCountDownLatch(1);Studentstudent=newStudent();student.study(()->{System.out.println("学生学习完了");countDownLatch.countDown();});try{countDownLatch.await();}catch(InterruptedExceptione){e.printStackTrace();}System.out.println("继续执行其他任务");

2、使用 CyclicBarrier

CyclicBarriercyclicBarrier=newCyclicBarrier(2);Studentstudent=newStudent();student.study(()->{System.out.println("学生学习完了");try{cyclicBarrier.await();}catch(InterruptedException|BrokenBarrierExceptione){e.printStackTrace();}});try{cyclicBarrier.await();}catch(InterruptedException|BrokenBarrierExceptione){e.printStackTrace();}System.out.println("继续执行其他任务");

3、使用 wait/notify + synchronized

privatevolatilebooleanfinished=false;

Objectlock=newObject();Studentstudent=newStudent();student.study(()->{synchronized(lock){System.out.println("学生学习完了");finished=true;lock.notify();}});try{synchronized(lock){while(!finished){lock.wait();}}}catch(InterruptedExceptione){e.printStackTrace();}System.out.println("继续执行其他任务");