Question

我在这里有一些代码。我试图解决《如何编程Java》一书中的问题。我总结了以下问题：

您需要在另一个类中实现以下设计以及main()方法来测试您的实现：   在以下位置实现层次结构：


MyShape是具有抽象Draw方法的抽象类，

MyBoundedShape是具有抽象GetArea方法的抽象类，

MyLine，MyOval，MyRectangle是具体的类


在main()方法中，


要求用户选择5种形状并输入其尺寸

绘制选定的形状

计算并显示所选形状（如果它们是有界形状）的面积

运行代码时，它没有显示面积或计算出的面积。

这是这些代码：

MyShape类

public abstract class MyShape 
{
    public abstract void Draw();
}

Myline类

public class Myline extends MyShape 
{
    private int length;
    public Myline (int length)
    {
           length=0;
    }
    public void setlength( int length )
    {
           length = 0; 
    } 
    public int getlength()
    {
           return length;
    } 
    public void Draw()
    {
           System.out.printf("Drawing a line with the length",getlength());
    }
}

Myextendedshape类

public abstract class MyextendedShape extends MyShape 
{
    protected double area;
    public abstract double getArea();

}

Myoval类

public class Myoval extends MyextendedShape
{
    private double Line1;
    private double Line2;
    public void Draw() 
    {
        System.out.println("I am drawing  a Oval");
    }

     Myoval()
    {
        Line1= 0.0;
        Line2 = 0.0;        
    }

    Myoval(double Line1, double Line2){
        this.Line1 =Line1;
        this.Line2 = Line2;
    }
    public double getLine1()
    {
        return Line1;
    }

    public void setLine1(double Line1)
    {
        this.Line1 = Line1;
    }

    public double getLine2()
    {
        return Line2;
    }

    public void setLine2(double Line2)
    {
        this.Line2 = Line2;
    }

    @Override
    public double getArea()
    {
        return calculateArea();
    }


    private double calculateArea()
    {
        return area = 3.14*Line1 * Line2;
    }

    public String toString()
    {
        return "The Line number 1 of the oval is: " + Line1 + " and the Line number 2 is: " + Line2 + ", "+ "and the area is: " + getArea();
    }

}

MyRectangle类

public class MyRectangle extends MyextendedShape {
    private double length, width;

    public void Draw() 
    {
        System.out.println("I am drawing  a Rectangle");
    }

    MyRectangle()
    {
        length= 0.0;
        width = 0.0;        
    }

    MyRectangle(double length, double width)
    {
        this.length =length;
        this.width = width;
    }



    public double getLenght() 
    {
        return length;
    }

    public void setLength(double length) 
    {
        this.length = length;
    }

    public double getWidth()
    {
        return width;
    }

    public void setWidth(double width) 
    {
        this.width = width;
    }

    @Override
    public double getArea()
    {
        return calculateArea();
    }


    private double calculateArea()
    {
        return area = width * length;
    }

    public String toString()
    {
        return "The width of the rectangle is: " + width + " and the length is: " + length + ", "+ "and the area is: " + getArea();
    }

}

Test

public class test 
{
     public static void main(String [] args) 
     {

         MyShape s = new Myline(6);
         s.Draw();

         s =  new Myoval(4.0, 5.0);
         s.Draw();

         s = new MyRectangle(4.0,6.0);
         s.Draw();

        }
}

Answer 1

您只在main中执行Draw()方法。如果您查看代码，则Draw()方法唯一要做的就是打印到屏幕“ I am drawing a [shape]”

如果您还想打印出每种形状的区域，则必须在main中调用“ getArea（）”方法（就像对“ Draw”所做的那样），或者使“ Draw”包含功能以输出区域。我将演示第一种方法。

public class test 
{
     public static void main(String [] args) 
     {

         MyShape s = new Myline(6);
         s.Draw();

         s =  new Myoval(4.0, 5.0);
         s.Draw();
         //This calculates the area of s, and then prints it to screen.
         System.out.println(s.getArea());

         s = new MyRectangle(4.0,6.0);
         s.Draw();
         System.out.println(s.getArea());

        }
}

请注意，代码中没有任何地方尝试实际绘制形状。我建议您重新阅读本书的部分内容，以达到目的。

如何显示区域？

1 个答案: