java - 使用执行服务同时执行多个对象的方法

Question

我正在尝试构建一个交通灯系统来控制路口。我有一个 Controller 类，它将执行路口的各个阶段，例如，第一阶段将使用 Thread.sleep 将南北和南北交通灯变为绿灯一段时间，然后在第二阶段中进行相同的操作相位，但适用于东西向和东西向交通灯。

我的问题是我想将每个阶段的所有交通灯一起打开，这样南北和南北交通灯就会同时变绿并变红。我尝试使用 ExecutedService 框架，但它似乎无法正常工作，这是我的代码。如果您需要任何进一步的信息以便给我有用的答案，请随时询问

这是 Controller 类的启动方法，它将连续运行阶段， Controller 将阶段作为对象 LinkedList 的列表。

public void start() throws Exception {

        // if there are no phases(cycles) to be executed in sequence
        if (phases.isEmpty()) {
            throw new Exception("There are no phases been created for the intersection to be controlled");
        }

        Iterator<Phase> iteratorP = phases.iterator();

        //execute phases in sequence
        while (iteratorP.hasNext()) {
            Phase phase = iteratorP.next();
            System.out.println("phase activated: ");
            // will activate the phase by turning all the traffic lights in this phase to green light
            phase.activate();

        }
    }

====================================== 这是阶段类。这个类将有一个交通灯列表，它将在一定时间内变成绿色，然后变成红色

protected void activate() {

        ExecutorService executorService = Executors.newFixedThreadPool(trafficLights.size());
        executorService.execute(new Runnable() {
            public void run() {
                for (TrafficLight tl : trafficLights) {

                    tl.nextState();
                    System.out.println("TrafficLight nextState done");

                    try {
                        //PrepareToStopSate = Amber Light
                        //PrepareToGoState = Amber + Red Lights

                        if (tl.getCurrentState() instanceof PrepareToStopState ||
                            tl.getCurrentState() instanceof PrepareToGoState) {
                            System.out.println("wait 2sec");

                            //will wait for two seconds then chnage the state to next state GoState or StopState
                            Thread.currentThread().sleep(pause * 1000);
                            System.out.println("TL nextState done");
                            tl.nextState();
                        } else {
                            //if the state of the traffic light is either GoState(green) or StopState(red)
                            //wait for (duration) time then change the state
                            System.out.println("wait duration for green and red");
                            Thread.currentThread().sleep(duration * 1000);
                        }
                    } catch (Exception e) {
                    }

                }
            }
        });

    }

Answer 1

根据我对您代码的理解，只有一个线程将运行 ExecutorService 的 execute 方法中的线程(您在代码中只执行一个 Runnable!)。

如果我的理解是正确的，您应该让每个 TrafficLight 实现 Runnable，然后编写如下代码:

protected void activate(){
//some code
ExecutorService executorService = Executors.newFixedThreadPool(trafficLights.size());    
for (TrafficLight tl: trafficLights){
          executor.execute(tl);
    }
//some other code
}

此外，您可能不想使用 Thread.sleep()，而是查看 CountDownLatch类。

对于具有 Runnable 的类，这就是您实现逻辑的地方，因此给定您的代码，它看起来像:

public class TrafficLight implement Runnable{

//Some methods
@Override
public void run(){

                    tl.nextState();
                    System.out.println("TrafficLight nextState done");

                    try {
                        //PrepareToStopSate = Amber Light
                        //PrepareToGoState = Amber + Red Lights

                        if (tl.getCurrentState() instanceof PrepareToStopState ||
                            tl.getCurrentState() instanceof PrepareToGoState) {
                            System.out.println("wait 2sec");

                            //will wait for two seconds then chnage the state to next state GoState or StopState
                            Thread.currentThread().sleep(pause * 1000);
                            System.out.println("TL nextState done");
                            tl.nextState();
                        } else {
                            //if the state of the traffic light is either GoState(green) or StopState(red)
                            //wait for (duration) time then change the state
                            System.out.println("wait duration for green and red");
                            Thread.currentThread().sleep(duration * 1000);
                        }
                    } catch (Exception e) {
                    }

                }
}