使用 Thread.sleep() 时 run() 方法出错

Question

我正在尝试在其自己的线程中运行 Elevator 实例。正在调用 run() 方法，但我的代码中一定有一些错误导致它无法运行。我的代码编译并运行没有错误，但从未打印过“电梯启动”。

我认为这与需要抛出 InterruptedException 的 Thread.sleep() 有关。我试图尝试/捕获异常，因为 Runnable 不会引发 InterruptedException。

你能帮我弄清楚为什么它没有运行吗？

这是我的 run() 方法：

@Override
public void run() {
    System.out.printf("Elevator starting up");

    while(true) {
        try {
            if (currentDirection == Direction.UP) {
                this.moveUp();
            }
            else if (currentDirection == Direction.DOWN) {
                this.moveDown();
            }
            else {Thread.sleep(250);}
        }
        catch (InterruptedException ie) {
            System.out.println("Elevator has experienced a critical error")
        }
    }
}

这是我在 Elevator 类中的 start() 方法。这是建筑物中每个电梯的主调用。

public void start() {
    activeThread = new Thread();
    activeThread.start();
}

moveUp() 方法：

public void moveUp() throws InterruptedException {
    Thread.sleep(travelSpeed);
    setCurrentFloor(currentFloor++);
}

moveDown() 方法：

public void moveDown() throws InterruptedException{
    Thread.sleep(travelSpeed);
    setCurrentFloor(currentFloor--);
}

完整的PassengerElevator.class代码

public class PassengerElevator implements ElevatorMover, Runnable {

private final int elevID;       // elevator number
private final int maxCapacity;  // max capacity of the elevator
private int currentCapacity;    // the current capacity of the elevator
private final long travelSpeed; // length of travel time between floors
private final long doorSpeed;   // length of time door stays open
private int currentFloor;       // the current floor the elevator is on
private final int defaultFloor; // the default floor after timeout
private Direction currentDirection; // the current direction the elevator is moving
public Thread activeThread = null;  // contains the instance of an elevator thread

/**
 * Constructor
 * @param elevID the ID number, as an int, given to the elevator
 */
public PassengerElevator(int elevID) {

    this.elevID = elevID;
    maxCapacity = 10;
    currentCapacity = 0;
    travelSpeed = 500;  // in milliseconds
    doorSpeed = 500;    // in milliseconds
    currentFloor = 1;
    defaultFloor = 1;
    currentDirection = Direction.IDLE;
}

/**
 * makes the elevator go up one floor. Takes travelSpeed time
 * @throws InterruptedException 
 */
@Override
public void moveUp() throws InterruptedException {
    Thread.sleep(travelSpeed);
    setCurrentFloor(currentFloor++);
}

/**
 * makes the elevator go down one floor. Takes travelSpeed time
 * @throws InterruptedException 
 */
@Override
public void moveDown() throws InterruptedException{
    Thread.sleep(travelSpeed);
    setCurrentFloor(currentFloor--);
}

/**
 * makes the elevator door open for doorSpeed time. When door is open people
 * move into elevator
 * @throws InterruptedException 
 */
@Override
public void openDoors() throws InterruptedException{
    Thread.sleep(doorSpeed);
}

public int getElevID() {
    return elevID;
}

private int getMaxCapacity() {
    return maxCapacity;
}

private int getCurrentCapacity() {
    return currentCapacity;
}

private void setCurrentCapacity(int x) {
    currentCapacity = x;
}

private double getTravelSpeed() {
    return travelSpeed;
}

private double getDoorSpeed() {
    return doorSpeed;
}

public int getCurrentFloor() {
    return currentFloor;
}

private void setCurrentFloor(int x) {
    currentFloor = x;
}

private int getDefaultFloor() {
    return defaultFloor;
}

private void setCurrentDirection(Direction x) {
    currentDirection = x;
}

private Direction getCurrentDirection() {
    return currentDirection;
}

/**
 * Starts a new thread for an elevator instance to run in
 */
public void start() {
    activeThread = new Thread();
    activeThread.start();
}

/**
 * The running loop for an elevator instance. Client will change current direction
 * and use the currentFloor as a check.
 */
@Override
public void run() {
    System.out.printf("Elevator starting up");

    while(true) {
        try {
            if (currentDirection == Direction.UP) {
                this.moveUp();
            }
            else if (currentDirection == Direction.DOWN) {
                this.moveDown();
            }
            else {Thread.sleep(250);}
        }
        catch (InterruptedException ie) {
            System.out.println("Elevator has experienced a critical error")
        }
    }

}

}

Answer 1

您正在直接创建一个Thread 实例，并且由于它是普通的Java Thread 类，它在run 方法中没有代码。这意味着当你启动它时，它什么也不做。这是相关代码：

public void start() {
    activeThread = new Thread();
    activeThread.start();
}

您需要启动一个线程来运行您的代码。要么让你的电梯类扩展Thread，要么实现Runnable。

扩展Thread时：

thread = new Elevator();
thread.start();

实现Runnable时：

thread = new Thread(new Elevator());
thread.start();

Thread documentation 提供了使用示例。