java之 ------ 抽象类

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封闭图像抽象类及其子类

Area.java：

public interface Area{

   public double area();
}

Circle.java：

public final class Circle extends Ellipse        //圆类，最终类 
{
    public Circle(double radius)                 //构造方法，radius参数指定圆的半径
    {
        super(radius,radius);
        this.shape = "圆";
    }
    public Circle()
    {
        this(0);
    }
    public String toString()
    {
        return "半径"+this.radius_a;
    }
    public static void main(String[] args) 
    {
        new Circle(10).print();
    }
}

ClosedFigure.java：

public abstract class ClosedFigure               //闭合图形抽象类
{
    protected String shape;                      //形状
    
    protected ClosedFigure(String shape)         //构造方法，不能是抽象方法
    {
        this.shape = shape;
    }
    protected ClosedFigure()
    {
        this("未知");
    }

    public abstract double area();               //计算面积，抽象方法，以分号";"结束 
    public abstract double perimeter();          //计算周长，抽象方法

    public void print()                          //显示形状、属性、周长及面积
    {
        System.out.println("一个"+this.shape+"，"+this.toString()
                           +"，周长为"+this.perimeter()+"，面积为"+this.area());
    }
}

class ClosedFigure_ex  
{
    public static void main(String args[])       //抽象类中可以包含main()方法
    {
        ClosedFigure g = new Ellipse(10,20);     //g引用椭圆对象
        g.print();                               //显示椭圆属性
        g = new Circle(10);                      //圆
        g.print();
        g = new Rectangle(10,20);                //g引用矩形对象
        g.print();                               //显示矩形属性
        g = new Square(10);                      //正方形
        g.print();
    }
}

Ellipse.java：

public class Ellipse extends ClosedFigure              //椭圆类 
{
    protected double radius_a;                   //a轴半径
    protected double radius_b;                   //b轴半径

    public Ellipse(double radius_a, double radius_b)//构造方法
    {
        super("椭圆");
        this.radius_a = radius_a;
        this.radius_b = radius_b;
    }
    public Ellipse()
    {
        this(0,0);
    }
    
    public String toString()
    {
        return "a轴半径"+this.radius_a+"，b轴半径"+this.radius_b;
    }
    
    public double area()                         //计算椭圆面积，覆盖父类的抽象方法
    {
        return Math.PI*this.radius_a*this.radius_b;
    }

    public double perimeter()                    //计算椭圆周长，覆盖父类的抽象方法
    {
        return Math.PI*(this.radius_a+this.radius_b);
    }

    public static void main(String args[])
    {
        new Ellipse(10,20).print();
    }
}

Rectangle.java：

public class Rectangle extends ClosedFigure            //矩形类
{
    protected double length;                     //长度
    protected double width;                      //宽度

    public Rectangle(double length, double width)//构造方法
    {
        super("矩形");
        this.length = length;
        this.width = width;
    }
    public Rectangle()
    {
        this(0,0);
    }
    public Rectangle(Rectangle r)
    {
        this(r.length, r.width);
    }
   
    public String toString()
    {
        return "长度"+this.length+"，宽度"+this.width;
    }
    
    public double area()                         //计算矩形面积，实现父类的抽象方法
    {
        return this.width*this.length;
    }
    public double perimeter()                    //计算矩形周长，实现父类的抽象方法
    {
        return (this.width+this.length)*2;
    }
    
    public void setLength(double length)
    {
        this.length = length;
    }

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

    public double getLength()
    {
        return this.length;
    }

    public double getWidth()
    {
        return this.width;
    }
    
    public static void main(String args[])
    {
        new Rectangle(10,20).print();
    }
}

Square.java：

public final class Square extends Rectangle      //正方形是长方形的特例
{
    public Square(double width)
    {
        super(width,width);
        this.shape = "正方形";
    }
    public Square()
    {
        this(0);
    }
    
    public String toString()
    {
        return "边长"+this.length;
    }
    
	public static void main(String[] args) 
	{
        new Square(10).print();
	}
}

java之 ------ 抽象类

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原文地址：http://blog.csdn.net/u011479875/article/details/45559321