Abstract Class 未初始化参数

Question

我正在尝试创建抽象 class SolidFigure。圆柱体和矩形棱柱体都将继承自它。

我的问题是，每当我实例化两个 classes 中的任何一个（圆柱或 rectPrism)

这是代码：

实体图：

public abstract class SolidFigure {

    private double height;

    public SolidFigure(double height) {
        height = this.height;
    }

    public double getHeight() {
        return height;
    }

    protected abstract boolean isEqual(SolidFigure s);

    protected abstract double calculateVolume();
}

柱面：

 class Cylinder extends SolidFigure{

   private double radius;
   private static double PI = 3.14;

   public Cylinder(double height, double radius) {
       super(height);
       this.radius = radius;
   }

   @Override
   protected double calculateVolume() {
        return radius * PI * getHeight();
   }

   @Override
   protected boolean isEqual(SolidFigure s) {
       return this.calculateVolume() == s.calculateVolume();
   }
}

直角棱镜：

   class RectPrism extends SolidFigure{
      private double length, width;

   public RectPrism(double height, double length, double width) {
       super(height);
       this.length = length;
       this.width = width;
   }

   @Override
   protected double calculateVolume() {
        return length * width * getHeight();
   }

   @Override
   protected boolean isEqual(SolidFigure s) {
       return this.calculateVolume() == s.calculateVolume();
   }
 }

主要：

    SolidFigure c = new Cylinder(12.0, 3);
    RectPrism r = new RectPrism(10.0, 4, 2);

    System.out.println(c.getHeight()); // This is zero
    System.out.println(r.calculateVolume()); // zero resulting from height

Answer 1

应该反过来

public SolidFigure(double height) {
        this.height = height;
    }

Answer 2

请更改

public SolidFigure(double height) {
        this.height = height;
    }

你的代码有什么问题

在您的代码中 height = this.height ; 这意味着您正在将实例变量 height 的值分配给参数 veriable height。它有默认值 0d 所以你得到这样的回答。

Abstract Class 未初始化参数

Abstract Class not initializing a parameter

java

class

inheritance

polymorphism

abstraction