我的问题涉及使用同步来订购我用于电梯程序的LinkedBlockingQueue。
在程序中，电梯应该尽可能高效：从第一层到第十层的电梯将在上行途中响应额外的停靠点，即使这些停靠点是在原来的10层之后进行的呼叫。
例如：电梯在一楼，并在大楼的10楼接到电话。在它前往十楼的过程中，7楼的一个人正在打电话。电梯在7楼停了下来，并在10日继续停止。
我的问题是，如何同步我的线程以有效地响应用户的呼叫？我不知道我在何处或如何插入同步。
下面是我的代码：它有一个工作的电梯和线程，但电梯不会有效地响应呼叫，而是发送每个不同的呼叫。为了表示旅行时间，我让电梯“休眠”3秒钟。
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。
答案 0 :(得分：4)
我会这样做，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