OOD - Design Elevator System

完整代码

Direction.java

package com.design.elevator;

public enum Direction {
    UP, DOWN
}

Status.java

package com.design.elevator;

public enum Status {
    UP, DOWN, IDLE
}

Request.java

package com.design.elevator;

public class Request {
    private int level;

    public Request(int l) {
        level = l;
    }

    public int getLevel() {
        return level;
    }

}

ExternalRequest.java

package com.design.elevator;

public class ExternalRequest extends Request{
    private Direction direction;

    public ExternalRequest(int l, Direction d) {
        super(l);
        // TODO Auto-generated constructor stub
        this.direction = d;
    }

    public Direction getDirection() {
        return direction;
    }
}

InternalRequest.java

package com.design.elevator;

public class InternalRequest extends Request{
    public InternalRequest(int l) {
        super(l);
        // TODO Auto-generated constructor stub
    }

}

ElevatorButton.java

package com.design.elevator;

public class ElevatorButton {
    private int level;
    private Elevator elevator;

    public ElevatorButton(int l, Elevator e) {
        this.level = l;
        this.elevator = e;
    }

    public void pressButton() {
        InternalRequest request = new InternalRequest(level);
        elevator.handleInternalRequest(request);
    }
}

Elevator.java

package com.design.elevator;

import java.util.ArrayList;
import java.util.List;

public class Elevator {

    private List<ElevatorButton> buttons;

    private List<Boolean> upStops;
    private List<Boolean> downStops;

    private int currLevel;
    private Status status;

    public Elevator(int n) {
        buttons = new ArrayList<ElevatorButton>();
        upStops = new ArrayList<Boolean>();
        downStops = new ArrayList<Boolean>();
        currLevel = 0;
        status = Status.IDLE;

        for (int i = 0; i < n; i++) {
            upStops.add(false);
            downStops.add(false);
        }
    }

    public void insertButton(ElevatorButton eb) {
        buttons.add(eb);
    }

    public void handleExternalRequest(ExternalRequest r) {
        if (r.getDirection() == Direction.UP) {
            upStops.set(r.getLevel() - 1, true);
            if (noRequests(downStops)) {
                status = Status.UP;
            }
        } else {
            downStops.set(r.getLevel() - 1, true);
            if (noRequests(upStops)) {
                status = Status.DOWN;
            }
        }
    }

    public void handleInternalRequest(InternalRequest r) {
        // check valid
        if (status == Status.UP) {
            if (r.getLevel() >= currLevel + 1) {
                upStops.set(r.getLevel() - 1, true);
            }
        } else if (status == Status.DOWN) {
            if (r.getLevel() <= currLevel + 1) {
                downStops.set(r.getLevel() - 1, true);
            }
        }
    }

    public void openGate() throws Exception {
        if (status == Status.UP) {
            for (int i = 0; i < upStops.size(); i++) {
                int checkLevel = (currLevel + i) % upStops.size();
                if (upStops.get(checkLevel)) {
                    currLevel = checkLevel;
                    upStops.set(checkLevel, false);
                    break;
                }
            }
        } else if (status == Status.DOWN) {
            for (int i = 0; i < downStops.size(); i++) {
                int checkLevel = (currLevel + downStops.size() - i) % downStops.size();
                if (downStops.get(checkLevel)) {
                    currLevel = checkLevel;
                    downStops.set(checkLevel, false);
                    break;
                }
            }
        }
    }

    public void closeGate() {
        if (status == Status.IDLE) {
            if (noRequests(downStops)) {
                status = Status.UP;
                return;
            }
            if (noRequests(upStops)) {
                status = Status.DOWN;
                return;
            }
        } else if (status == Status.UP) {
            if (noRequests(upStops)) {
                if (noRequests(downStops)) {
                    status = Status.IDLE;
                } else {
                    status = Status.DOWN;
                }
            }
        } else {
            if (noRequests(downStops)) {
                if (noRequests(upStops)) {
                    status = Status.IDLE;
                } else {
                    status = Status.UP;
                }
            }
        }
    }

    private boolean noRequests(List<Boolean> stops) {
        for (int i = 0; i < stops.size(); i++) {
            if (stops.get(i)) {
                return false;
            }
        }
        return true;
    }


    public String elevatorStatusDescription() {
        String description = "Currently elevator status is : " + status
                + ".\nCurrent level is at: " + (currLevel + 1)
                + ".\nup stop list looks like: " + upStops
                + ".\ndown stop list looks like:  " + downStops
                + ".\n*****************************************\n";
        return description;
    }

}

模拟流程

Simulation.java

package com.design.elevator;

public class Simulation {

    public static void main(String[] args) throws Exception {
        // 初始化电梯对象
        Elevator elevator = new Elevator(5);
        // 实例化 request对象
        ExternalRequest e1 = new ExternalRequest(3, Direction.DOWN);

        elevator.handleExternalRequest(e1);

        System.out.println(elevator.elevatorStatusDescription());


        ExternalRequest e2 = new ExternalRequest(2, Direction.UP);

        elevator.handleExternalRequest(e2);
        System.out.println(elevator.elevatorStatusDescription());

        elevator.openGate();
        elevator.closeGate();
        elevator.openGate();
        elevator.closeGate();

        System.out.println(elevator.elevatorStatusDescription());
    }
}