当我研究闩锁和循环障碍时,我想到了这个比喻。
循环障碍:想象一家公司有一个会议室。为了开始会议,必须有一定数量的与会者参加会议(使其正式)。以下是普通会议参加者(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!>");
}
}
}
员工加入会议,等待其他人来开始会议。如果会议被取消,他也会退出:) 然后我们有老板不喜欢等待其他人出现,如果他失去了他的病人,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,员工来开会等待其他人出现,如果一些与会者不来,他们必须无限期地等待!某次特殊会议,老板来了,他不喜欢等。(需要5个人开会,但只有老板来,还有一个热情的员工)所以他取消了会议(生气)
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!>
还有另一种情况是另一个外线线程(地震)取消了会议(呼叫重置方法)。在这种情况下,所有等待的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();
}
}
运行代码将产生有趣的输出:
// 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!>
您还可以在会议室中添加秘书,如果举行会议,她会记录所有事情但她不是会议的一部分:
class MeetingSecretary implements Runnable {
@Override
public void run() {
System.out.println("preparing meeting documents");
System.out.println("taking notes ...");
}
}
闩锁:如果生气的老板要为公司客户举办展览,那么一切都需要准备好(资源)。我们为每个工人(线程)提供了一份待办事项清单,我们检查了待办事项清单(一些工人做绘画,其他人准备音响系统......)。当待办事项列表中的所有项目都完成(提供资源)时,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");
}
}
工人们如何准备展览:
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();