当我研究闩锁和循环壁垒时，我想到了这个隐喻。
循环屏障：想象一家公司有一个会议室。为了开始会议，一定数量的会议参与者必须参加会议（使其正式化）。以下是普通会议与会者（员工）的代码
class MeetingAtendee implements Runnable {
CyclicBarrier myMeetingQuorumBarrier;
public MeetingAtendee(CyclicBarrier myMileStoneBarrier) {
this.myMeetingQuorumBarrier = myMileStoneBarrier;
}
@Override
public void run() {
try {
System.out.println(Thread.currentThread().getName() + " i joined the meeting ...");
myMeetingQuorumBarrier.await();
System.out.println(Thread.currentThread().getName()+" finally meeting stared ...");
} catch (InterruptedException e) {
e.printStackTrace();
} catch (BrokenBarrierException e) {
System.out.println("Meeting canceled! every body dance <by chic band!>");
}
}
}
员工参加会议，等待其他人开始会议。如果会议被取消，他也会退出会议：)然后，老板让我们知道不喜欢等别人出现的剂量，如果他放松了耐心，他会取消会议。
class MeetingAtendeeTheBoss implements Runnable {
CyclicBarrier myMeetingQuorumBarrier;
public MeetingAtendeeTheBoss(CyclicBarrier myMileStoneBarrier) {
this.myMeetingQuorumBarrier = myMileStoneBarrier;
}
@Override
public void run() {
try {
System.out.println(Thread.currentThread().getName() + "I am THE BOSS - i joined the meeting ...");
//boss dose not like to wait too much!! he/she waits for 2 seconds and we END the meeting
myMeetingQuorumBarrier.await(1,TimeUnit.SECONDS);
System.out.println(Thread.currentThread().getName()+" finally meeting stared ...");
} catch (InterruptedException e) {
e.printStackTrace();
} catch (BrokenBarrierException e) {
System.out.println("what WHO canceled The meeting");
} catch (TimeoutException e) {
System.out.println("These employees waste my time!!");
}
}
}
在正常的一天，员工来开会等其他人出现，如果一些与会者不来，他们必须无限期地等待！在某些特殊的会议上，老板来了，他不想等待。（需要5个人开始会议，但只有老板来了，还有一个热情的员工），所以他（愤怒地）取消了会议。
CyclicBarrier meetingAtendeeQuorum = new CyclicBarrier(5);
Thread atendeeThread = new Thread(new MeetingAtendee(meetingAtendeeQuorum));
Thread atendeeThreadBoss = new Thread(new MeetingAtendeeTheBoss(meetingAtendeeQuorum));
atendeeThread.start();
atendeeThreadBoss.start();
输出：
//Thread-1I am THE BOSS - i joined the meeting ...
// Thread-0 i joined the meeting ...
// These employees waste my time!!
// Meeting canceled! every body dance <by chic band!>
在另一种情况下，另一个外部线程（地震）取消了会议（呼叫重置方法）。在这种情况下，所有等待线程都会被异常唤醒。
class NaturalDisasters implements Runnable {
CyclicBarrier someStupidMeetingAtendeeQuorum;
public NaturalDisasters(CyclicBarrier someStupidMeetingAtendeeQuorum) {
this.someStupidMeetingAtendeeQuorum = someStupidMeetingAtendeeQuorum;
}
void earthQuakeHappening(){
System.out.println("earth quaking.....");
someStupidMeetingAtendeeQuorum.reset();
}
@Override
public void run() {
earthQuakeHappening();
}
}
运行代码将导致有趣的输出：
// Thread-1I am THE BOSS - i joined the meeting ...
// Thread-0 i joined the meeting ...
// earth quaking.....
// what WHO canceled The meeting
// Meeting canceled! every body dance <by chic band!>
您还可以在会议室添加秘书，如果召开会议，她将记录所有事情，但她不属于会议：
class MeetingSecretary implements Runnable {
@Override
public void run() {
System.out.println("preparing meeting documents");
System.out.println("taking notes ...");
}
}
闩锁：如果生气的老板想为公司客户举办展览，则需要做好一切准备（资源）。我们为每个工作人员（线程）提供一份待办事项清单，并检查待办事项清单（一些工人在做画，其他人在准备音响系统...）。当待办事项清单中的所有项目都完成时（提供了资源），我们可以为客户打开大门。
public class Visitor implements Runnable{
CountDownLatch exhibitonDoorlatch = null;
public Visitor (CountDownLatch latch) {
exhibitonDoorlatch = latch;
}
public void run() {
try {
exhibitonDoorlatch .await();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("customer visiting exebition");
}
}
以及工人如何准备展览：
class Worker implements Runnable {
CountDownLatch myTodoItem = null;
public Worker(CountDownLatch latch) {
this.myTodoItem = latch;
}
public void run() {
System.out.println("doing my part of job ...");
System.out.println("My work is done! remove it from todo list");
myTodoItem.countDown();
}
}
CountDownLatch preperationTodoList = new CountDownLatch(3);
// exhibition preparation workers
Worker electricalWorker = new Worker(preperationTodoList);
Worker paintingWorker = new Worker(preperationTodoList);
// Exhibition Visitors
ExhibitionVisitor exhibitionVisitorA = new ExhibitionVisitor(preperationTodoList);
ExhibitionVisitor exhibitionVisitorB = new ExhibitionVisitor(preperationTodoList);
ExhibitionVisitor exhibitionVisitorC = new ExhibitionVisitor(preperationTodoList);
new Thread(electricalWorker).start();
new Thread(paintingWorker).start();
new Thread(exhibitionVisitorA).start();
new Thread(exhibitionVisitorB).start();
new Thread(exhibitionVisitorC).start();