抽象方法的體現--->模版模式

package com.xbmd.abstractmode;
 
public abstract class Graphics 
{
 
    //面積
    abstract double area();
    //周長
    abstract double perimeter();
    //模版，不準別人更改
    public final void print()
    {
        System.out.println("面積:"+area());
        System.out.println("周長:"+perimeter());
    }
}

package com.xbmd.abstractmode;
//¾²Ì¬µ¼ÈëMathÀàÖеľ²Ì¬×Ö¶ÎPI
import static java.lang.Math.PI;
public class Circle extends Graphics {
 
    //Ô²°ë¾¶
    private double r;
    public Circle(double r)
    {
        this.r=r;
    }
    double area() {
        return PI*r*r;
    }
    double perimeter() {
        return 2*PI*r;
    }
}

package com.xbmd.abstractmode;
 
public class Rectangle extends Graphics {
 
    private double a;
    private double b;
    public Rectangle(double a,double b)
    {
        this.a=a;
        this.b=b;
    }
    double area() {
        return a*b;
    }
    double perimeter() {
        return 2*(a+b);
    }
 
}

package com.xbmd.abstractmode;
 
public class Triangle extends Graphics {
 
    //Èý±ßÖ®³¤
    private double a;
    private double b;
    private double c;
    public Triangle(double a,double b,double c)
    {
        this.a=a;
        this.b=b;
        this.c=c;
    }
    double area() {
        double p = (a+b+c)/2;
        return Math.sqrt(p*(p-a)*(p-b)*(p-c));
    }
    double perimeter() {
        return a+b+c;
    }
 
}

package com.xbmd.abstractmode;
/**
 * 抽象方法的體現：模版模式
 * 需求:
 *      1.求不同圖形(三角形，矩形，圓)的面積，周長。
 *      2.寫一個打印方法，將其面積和周長打印出來
 */
public class AbstractModeDemo{
    public static void main(String[] args) {
        System.out.println("圓--->");
        Circle c = new Circle(5);
        c.print();
        System.out.println("三角形--->");
        Triangle t = new Triangle(3,4,5);
        t.print();
        System.out.println("矩形--->");
        Rectangle r = new Rectangle(4, 5);
        r.print();
         
    }
}