App8_10_抽象类abstract

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//抽象类abstract--like C++ 模板abstract class Shape{protected String name;public Shape(String xm)//抽象类中的一般方法，构造方法{name=xm;System.out.print("名称"+name);}abstract public double getArea();       //声明抽象方法(只需声明)abstract public double getLength();     //声明抽象方法}//class Circle extends Shape    //定义继承自Shape的子类Circle{private final double PI=3.14;private double radius;public Circle(String shapeName,double r)   //构造方法{super(shapeName);                      //调用父类中的有参构造方法 必须在第一行radius=r;}public double getArea()     //实现抽象类中的方法{return PI*radius*radius;}public double getLength()   //实现抽象类中的方法{return 2*PI*radius;}}//class Rectangle extends Shape   //定义继承自Shape的子类Rectangle{private double width;private double height;public Rectangle(String shapeName,double width,double height){super(shapeName);this.width=width;this.height=height;}public double getArea(){return width*height;}public double getLength(){return 2*width*height;}}//public class App8_10 {                        //主类public static void main(String[] args){Shape rect=new Rectangle("长方形",6.5,10.3);System.out.println("；面积="+rect.getArea());System.out.println("；周长="+rect.getLength());Shape circle=new Circle("圆",10.2);System.out.println("；面积="+circle.getArea());System.out.println("；周长="+circle.getLength());}}
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