Java继承——从父类获取参数

Question

我想从 Car 的父类中获取一个参数并将其添加到我的数组 (carsParked)，我该怎么做？

父类

public class Car
{
    protected String regNo;       //Car registration number
    protected String owner;       //Name of the owner
    protected String carColor;

    /** Creates a Car object
     * @param rNo - registration number
     * @param own - name of the owner
     **/
    public Car (String rNo, String own, String carColour)
    {
        regNo = rNo;
        owner = own;
        carColor = carColour;
    }

    /** @return The car registration number
     **/
    public String getRegNo()
    {
        return regNo;
    }

    /** @return A String representation of the car details
     **/
    public String getAsString()
    {
        return "Car: " + regNo  + "\nColor: " + carColor;

    }
    public String getColor()
    {
        return carColor;
    }
}

子类

public class Carpark extends Car
{
    private String location;        // Location of the Car Park  
    private int capacity;           // Capacity of the Car Park - how many cars it can hold 
    private int carsIn;             // Number of cars currently in the Car Park   
    private String[] carsParked;

    /** Constructor for Carparks
     * @param loc - the Location of the Carpark
     * @param cap - the Capacity of the Carpark
     */
    public Carpark (String locations, int room)
    {

        location = locations;
        capacity = room;
    }
    /** Records entry of a car into the car park */
    public void driveIn()
    {
         carsIn = carsIn + 1;



    }

    /** Records the departure of a car from the car park */
    public void driveOut()
    {
        carsIn = carsIn - 1;
    }

    /** Returns a String representation of information about the carpark */
    public String getAsString()
    {
        return location + "\nCapacity: " + capacity +
             "  Currently parked:  " + carsIn + 
             "\n*************************\n";
    }

}

最后一题法

public String getCarsByColor (String carColour)

{

  for (int num = 0; num < carsParked.length; num++)
    {
        if ( carColour.equals(carsParked[num]) )
        {
            System.out.print (carsParked[num]);

        }
    }
return carColour;

}

到目前为止，如果在参数中输入“red”，它会列出所有红色的汽车及其相应的信息，但似乎不起作用 ~_~。

Answer 1

您在这里的关系似乎有误: parking 场不是汽车。我建议不要在这些类之间的任何方向上使用继承。和 Carpark应该只有一组或一组汽车。

还要注意参数 carsIn没有必要 - 只需获取 length汽车阵列(或 size() 如果它是 Collection )。

编辑: 好吧，忽略继承部分，似乎在 driveIn 时添加汽车是有意义的被调用，并在 driveOut 时删除它们被称为。

driveIn可能应该采取 Car作为参数，因此该方法可以访问您要存储的参数(我个人只存储 Car 引用，但没问题)。因为我们要添加和删除这些参数，所以使用 List 会容易得多。可以调整自身大小而不是数组，例如 ArrayList .例如:

private final List<String> carsRegNosParked = new ArrayList<String>();

public void driveIn(Car car) {
    carsRegNosParked.add(car.getRegNo());
}

不太清楚 driveOut 是什么应该做。可能需要特定的注册号才能删除:

public void driveOut(String regNo) {
    carsRegNosParked.remove(regNo);
}

或者它可以不分青红皂白地删除一辆车，比如添加的第一辆车:

public void driveOut() {
    if (!carsRegNosParked.isEmpty()) {
        carsRegNosParked.remove(0);
    }
}

注意 remove(Object) 之间的区别和 remove(int) .