Abstract类未初始化参数

Posted 2021-03-30

我正在尝试创建一个抽象类SolidFigure。圆柱形和长方形的pirsm都会从它开始。

我的问题是每当我实例化两个类中的任何一个（cylinder或rectPrism）时，构造函数（它将为零）初始化SolidFigure中的高度（它是一个公共属性）

这是代码：

SolidFigure：

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();
}

圆筒：

 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();
   }
}

RectPrism：

   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

答案

它应该是相反的方式

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

另一答案

请更换

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

你的代码有什么问题

在你的代码height = this.height ;中，这意味着你将实例变量height的值赋给参数可验证的高度。它有默认值0d所以你得到这样的aswer。