抽象类、方法的定义及实现

package day_15;
/**
 * 定义一个平面图形抽象类
 */
public abstract class PlaneFigure {
    public abstract double getArea();   //定义得到面积的抽象方法
    public abstract double getPerimeter();  //定义得到周长的抽象方法
}
package day_15;
//定义一个矩形类
public class Rectangle extends PlaneFigure {
    private double wide;
    private double length;

    public Rectangle(){

    }
    public Rectangle(double wide, double length) {
        this.wide = wide;
        this.length = length;
    }

    public  double getArea(){    //重写得到面积的抽象方法
        return wide*length;
    }
    public double getPerimeter(){  //重写得到周长的抽象方法
        return 2*(wide+length);
    }
}
package day_15;
//定义一个圆类
public class Circle extends PlaneFigure{
    private double r;
    private static final double PI=3.14;

    public Circle(){

    }
    public Circle(double r) {
        this.r = r;
    }

    @Override
    public double getArea() {  //
        return PI*r*r;
    }

    @Override
    public double getPerimeter() {
        return 2*PI*r;
    }
}
package day_15;

public class Test {
    public static void main(String[] args) {
        Circle circle=new Circle(3);
        print(circle);
        Rectangle rectangle=new Rectangle(3,4);
        print(rectangle);
    }
    public static void print(PlaneFigure planeFigure){    //定义静态方法
        System.out.println("当前平面图形的信息:");
        System.out.println("\t面积:"+planeFigure.getArea());
        System.out.println("\t周长:"+planeFigure.getPerimeter());
    }
}