java 中的简单摘要 class

Question

所以我需要为容器实现一个 getCurrentVolumeInCCs 方法 class，但是我对如何实现有点困惑。此外，我在 Glass 和 Cup classes 中获得了正确的体积值，但是当我在 Vessel class 中调用任何其他方法时，这些值不会被保留。我猜是因为它们存储在 subclass 中，不能在 base class 中使用，对吗？

船只 Class（摘要）

package containers;

public abstract class Vessel {
    private double volume; 
    private double currentVolume;
    public Vessel() {
        volume = 0;
        currentVolume = 0;
    }

    abstract double getVolumeInCC();

    public double getCurrentContents() {


        return currentVolume;
    }

    public double drink(double amountToDrink) {
        double volumeLeft; 

        System.out.println("you drank " + amountToDrink + " CCs");
        volumeLeft = volume - amountToDrink;

        return volumeLeft;
    }

    public double fill(double amountPoured) {
        double volumeAdded = amountPoured;
        double volumeSpilled = 0;

        System.out.println("you poured " + amountPoured + " CCs");
        if(volumeAdded > volume) {
            volumeSpilled = amountPoured - volume;
            System.out.println("you spilled " + volumeSpilled);

        }
        return volumeAdded;
    }

}

玻璃 Class

package containers;

public class Glass extends Vessel{
    private double volume;
    private double radiusBase;
    private double height; 

    public Glass() {}

    public Glass(double r, double h) {
        this.radiusBase = r;
        this.height = h;
    }

    @Override
    double getVolumeInCC() {
        volume = (Math.PI)*(Math.pow(radiusBase, 2))*height;

        return volume;
    }
}

杯子Class

package containers;

public class Cup extends Vessel {
    private double volume;
    private double radiusLip;


    public Cup(double r) { 
        volume = 0;
        this.radiusLip = r;

    }

    @Override
    double getVolumeInCC() {
        volume = (0.5)*(Math.PI)*(Math.pow(radiusLip, 3))*(4/3);

        return volume;
    }

}

Answer 1

您在子类中从 Vessel 隐藏 volume，因为它是一个 private 字段。我相信您想让 volume 和 currentVolume 在 Vessel、

中受到保护

protected double volume; 
protected double currentVolume;

此外，您应该从子类中删除 private double volume（这样您就不会隐藏他们现在从 Vessel 继承的字段）。

java 中的简单摘要 class

simple abstract class in java

java

class

abstract