java - 如何使用同步来订购我的 LinkedBlockingQueue？

Question

我的问题涉及使用同步来订购我用于电梯程序的 LinkedBlockingQueue。

在该程序中，电梯应该尽可能高效地运行:从一楼到十楼的电梯将在上升过程中响应额外的停靠，即使这些停靠是在最初的 10 楼之后进行的称呼。

例如:电梯在一楼，在大楼的 10 楼接到电话。在它上到十楼的过程中，一个在上楼的七楼的人打了个电话。电梯停在7楼，继续到10楼原站。

我的问题是，我如何同步我的线程以有效地响应用户的调用？我不确定我在哪里或如何插入同步。

下面是我的代码:它有一个工作电梯和线程，但电梯不会有效地响应调用，而是在发送每个不同的调用时。为了表示旅行时间，我让电梯“hibernate ”了 3 秒。

public class Elevator {
public Thread main;
public Thread thread2;
LinkedBlockingQueue<Integer> lb = new LinkedBlockingQueue<Integer>();
public int num1;

public static void main(String[] args) {
    Elevator ele = new Elevator();
}

public Elevator() {
    main = new Thread(new Task1());
    thread2 = new Thread(new Task2());
    main.start();
    thread2.start();
}

public class Task1 implements Runnable {

    @Override
    public void run() {

        // create loop with whcih the program asks for floors
        // add the scanner int to the arraylist queue

        while (thread2.isAlive()) {
            System.out.println("Choose a Floor: 1-10");
            Scanner s = new Scanner(System.in);
            int floorInput = s.nextInt();

            if (floorInput > 10 || floorInput < 0) {
                System.out.println("Floor does not exist.");
            } else if (floorInput == 0) {
                System.out.println("You have exitted the elevator.");
                System.exit(0);
            } else {

                lb.add(floorInput);
                System.out.println("floor inputed into the queue.");
                // System.out.println(lb);
                // j++;

            }
        }
    }
}

public class Task2 implements Runnable {

    @Override
    public void run() {

        // motor class
        // looks in the queue and goes to the floors

        // while (!lb.isEmpty())
        int i = 0;
        int s = 0;
        while (i < 5) { //endless loop, neccessary for an elevator
            if (lb.contains(2)) {
                try {
                    System.out.println("Travelling to 2nd Floor...");
                    Thread.sleep(3000);
                    s = lb.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Arrived on 2nd Floor.");
                System.out.println("removed: " + s);
            } else if (lb.contains(1)) {
                try {
                    System.out.println("Travelling to 1st Floor...");
                    Thread.sleep(3000);
                    s = lb.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Arrived on 1st Floor.");
                System.out.println("removed: " + s);
            } else if (lb.contains(3)) {
                try {
                    System.out.println("Travelling to 3rd Floor...");
                    Thread.sleep(3000);
                    s = lb.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Arrived on 3rd Floor.");
                System.out.println("removed: " + s);
            } else if (lb.contains(4)) {
                try {
                    System.out.println("Travelling to 4th Floor...");
                    Thread.sleep(3000);
                    s = lb.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Arrived on 4th Floor.");
                System.out.println("removed: " + s);
            } else if (lb.contains(5)) {
                try {
                    System.out.println("Travelling to 5th Floor...");
                    Thread.sleep(3000);
                    s = lb.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Arrived on 5th Floor.");
                System.out.println("removed: " + s);
            } else if (lb.contains(6)) {

                try {
                    System.out.println("Travelling to 6th Floor...");
                    Thread.sleep(3000);
                    s = lb.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Arrived on 6th Floor.");
                System.out.println("removed: " + s);
            } else if (lb.contains(7)) {
                try {
                    System.out.println("Travelling to 7th Floor...");
                    Thread.sleep(3000);
                    s = lb.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Arrived on 7th Floor.");
                System.out.println("removed: " + s);
            }

            else if (lb.contains(8)) {
                try {
                    System.out.println("Travelling to 8th Floor...");
                    Thread.sleep(3000);
                    s = lb.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Arrived on 8th Floor.");
                System.out.println("removed: " + s);
            }

            else if (lb.contains(9)) {
                try {
                    System.out.println("Travelling to 9th Floor...");
                    Thread.sleep(3000);
                    s = lb.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Arrived on 9th Floor.");
                System.out.println("removed: " + s);
            } else if (lb.contains(10)) {
                try {
                    System.out.println("Travelling to 10th Floor...");
                    Thread.sleep(3000);
                    s = lb.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Arrived on 10th Floor.");
                System.out.println("removed: " + s);
            }

        }
    }
}

任何帮助将不胜感激。

Answer 1

我会做不同的，这是基本的想法:

class Elevator extends Thread {
    NavigableSet<Integer> calls = new ConcurrentSkipListSet<>();
    int floor = 1;

    @Override
    public void run() {
        for (;;) {
            try {
                Thread.sleep(100);
                while (calls.higher(floor) != null) {
                    move(+1);
                }
                while (calls.lower(floor) != null) {
                    move(-1);
                }
            } catch (InterruptedException e) {
            }
        }
    }

    void move(int n) throws InterruptedException {
        floor += n;
        System.out.println("Moving to " + floor);
        Thread.sleep(3000);
        if (calls.remove(floor)) {
            System.out.println("Stopped");
            Thread.sleep(3000);
        }
    }

    void call(int floor) {
        calls.add(floor);
    }
}

测试

    Elevator e = new Elevator();
    e.start();
    e.call(2);
    e.call(4);
    e.call(1);

输出

Moving to 2
Stopped
Moving to 3
Moving to 4
Stopped
Moving to 3
Moving to 2
Moving to 1
Stopped