java - 在java中使用this保存多个对象引用

Question

我有以下建筑类:

public class Building {

static ArrayList<Floor> floors = new ArrayList<Floor>();
public Elevator elevator;
public static int floorNo;

//constructor creates elevator and floor objects
public Building() {
    elevator = new Elevator(Elevator.building);

    int count = 1;
    while (count != FLOORS+1) {
        floors.add(new Floor(Elevator.building, count));
        count++;
    }
}

//returns proper floor object by accessing the array
public static Floor floor(int floorNumber) {
    this.floorNo = floorNumber;
    return floors.get(floorNumber-1);
}

public static int getFloorNo() {
    return floorNo;
}

}

如果我创建以下对象并对其调用某些方法。我丢失了对象的标识，当我调用该方法时，我不知道它正在调用哪个对象。

//I save the 1 using this in floor(), so floorNo = 1
Floor firstFloor = building.floor(1);   

//now floorNo = 2
Floor secondFloor = building.floor(2); 

//here how do I know that firstFloor is 1 since floorNo value is changed
firstFloor.waitForElevator();

谢谢!

Answer 1

实际上，您使用采用楼层号(第二个参数)的构造函数创建了 firstFloor。

我猜你的Floor类看起来像这样:

public class Floor {
   private final int floorNo;
   private final Elevator elevator;

   public Floor(final Elevator elevator, final int floorNo) {
       this.elevator = elevator;
       this.floorNo = floorNo;
   }
}

要获取 firstFloor 的 floorNo(它只是 Floor 的一个实例)，您应该创建(并使用!)一个 <其floorNo字段的strong>getter。

例如，您可以将以下方法添加到 Floor 类中:

public int getFloorNo() {
    return this.floorNo;
)

因此，您可以知道 Floor 任何实例的楼层号，如下所示:

System.out.println(firstFloor.getFloorNo());

将输出:

1