[OOD设计] - 电梯系统设计

news2025/11/4 11:00:25

明确主要需求

首先需要设计电梯系统的基本工作流程，一个简单电梯系统主要就是两个主要功能：

乘客在电梯外按下按钮时，电梯系统会驱动一个电梯来接人
乘客在电梯内部按下楼层按钮时，电梯系统会驱动该电梯到达指定楼层

根据需求来创建必要对象及属性

电梯系统类 - ElevatorSystem

用来管理系统中所有电梯类，并保存电梯调度算法 - (当乘客在外部摁键时，通过算法分配一个电梯去接人)

class ElevatorSystem {

    List<Elevator> elevators;
    Date datetime;

    private static final ElevatorSystem instance = new ElevatorSystem();

    private ElevatorSystem() {
        elevators = new ArrayList<>();
    }

    public static ElevatorSystem getInstance() {
        return instance;
    }

    public void addElevator(Elevator e) {
        elevators.add(e);
    }

    public Elevator assignElevator(Request req) {
        // 选一个IDLE状态的电梯，如果没有则找一个最不忙的电梯
        Elevator res = elevators.get(0);
        for (Elevator tmp: elevators) {
            if (tmp.status == Direction.IDLE) return tmp;
            else if (tmp.checkWorkLoad() < res.checkWorkLoad()) res = tmp;
        }

        return res;
    }
}

电梯类 - Elevator

用于保存电梯的各种属性(当前层，当前状态，最大承重，能到达的最高楼层)，以及电梯接送人的顺序逻辑

我们建立两个HashSet 来分别保存乘客向上和向下的请求，使用HashSet的优点是可以过滤掉重复请求，没到达一层时直接查找HashSet来决定停还是不停。

class Elevator {
    int currFloor; // 当前楼层
    Direction status; // 电梯当前方向
    int maxFloor;
    int maxWeight;

    HashSet<Integer> upQueue = new HashSet<>();
    HashSet<Integer> downQueue = new HashSet<>();

    public Elevator(int maxFloor, int maxWeight) {
        this.maxFloor = maxFloor;
        this.maxWeight = maxWeight;
        currFloor = 1;
        status = Direction.IDLE;
    }

    public void handleRequest(Request req) {
        if (req.dir == Direction.DOWN) {
            downQueue.add(req.floor);
        } else {
            upQueue.add(req.floor);
        }
    }

    public int checkWorkLoad() {
        // 查看当前电梯繁忙程度
        return downQueue.size() + upQueue.size();
    }

    public boolean run() {
        try {
            // status refresh
            // when reach 1st floor then switch status to up
            // when reach top floor than switch status to down
            // if status is down but not req in downQ then switch status to UP
            // if status is up but not req in upQ then swith status to Down
            // if no req then switch to IDLE
            if (currFloor==1 && status==Direction.DOWN) {
                status = Direction.UP;
            } else if (currFloor==maxFloor && status==Direction.UP) {
                status = Direction.DOWN;
            } else if (checkWorkLoad()==0) {
                status = Direction.IDLE;
            } else if (upQueue.size()==0) {
                status = Direction.DOWN;
            } else if (downQueue.size()==0) {
                status = Direction.UP;
            }

            // move to next stop
            // if status is down then find next stop and move
            // if status is up then find next stop and move
            if (status == Direction.DOWN) {
                for (int i = currFloor; i>=1; i--) {
                    if (downQueue.contains(i)) {
                        downQueue.remove(i);
                        currFloor = i;
                        return true;
                    }
                }
            } else if (status == Direction.UP) {
                for(int i = currFloor; i<=maxFloor; i++) {
                    if (upQueue.contains(i)) {
                        upQueue.remove(i);
                        currFloor = i;
                        return true;
                    }
                }
            }
        } catch (Exception ex) {
            System.out.println("Alert!!! call the emergency office");
        }
        return false;

    }
}

按键类 (或者请求类) - Request (InternalRequest/ExternalRequest)

这是一个抽象类，并被内部摁键类和外部摁键类继承，用于保存每一个乘客请求的具体信息

enum Direction  {
    UP, DOWN, IDLE
}

abstract class Request {
    int floor;
    Direction dir;
}

class ExternalRequest extends Request {
    int floor;
    Direction dir;

    public ExternalRequest(int f, Direction d) {
        floor = f;
        dir = d;
    }
}

class InternalRequest extends Request {
    int floor;
    Direction dir;

    public InternalRequest(int f, Direction d) {
        floor = f;
        dir = d;
    }
}

(非必要) 乘客类 - Passenger

保存乘客摁键行为的类

按外部按键
按内部按键

class Passenger {
    ElevatorSystem instance = ElevatorSystem.getInstance();
    Elevator assignedElv = null;

    public boolean pressExtButton(int floor, Direction dir) {
        assignedElv = instance.assignElevator(new ExternalRequest(floor, dir));
        return true;
    }

    public boolean pressIntButton(int floor) {
        Direction dir = Direction.IDLE;
        if (floor > assignedElv.currFloor) assignedElv.handleRequest(
                new InternalRequest(floor, Direction.UP));
        else if (floor > assignedElv.currFloor) assignedElv.handleRequest(
                new InternalRequest(floor, Direction.DOWN));
        else return false;
        return true;
    }
}