※ 引述《cscfish (雙棲動物)》之銘言：
> 就是為啥我計算出的數字都會是0 是哪要改嗎
> 還有說要用多形和超載 那應該超載已經合多型條件了吧
> 如果不合條件 那要怎麼改才可以呢
> 因為getarea() 同時有計triangle circle rectangle的不同功能(多形)
> class shape {
> private double area,circum;
> shape(double a,double b)
> {
> this.area=a;
> this.circum=b;
> }
> public double getarea(){return area;}
> double getcircum(){return circum;}
> }
> =====================================================
> class circle extends shape {
> private double r;
> circle(double r)
> {super(r,r);}
> public double getarea(){return 3.14*r*r;}
> public double getcircum(){return 6.28*r;};
> }
> =====================================================
> class rectangle extends shape{
> private double x,y;
> rectangle(double x,double y)
> {super(x,y);}
> public double getarea(){return x*y;}
> public double getcircum(){return 2*x+2*y;};
> }
> =====================================================
> class triangle extends shape {
> double s,t;
> triangle(double s,double t)
> { super(s,t);}
> public double getarea(){return 0.5*s*t;}
> public double getcircum(){return 3*s;};
> }
> =====================================================
> public class calculate {
> public static void main(String args[]){
> circle cir=new circle(3);
> triangle tri=new triangle(3,3);
> rectangle rec=new rectangle(3,3);
> System.out.print("\n" +cir.getarea());
> System.out.print("\n" +cir.getcircum());
> System.out.print("\n" +tri.getarea());
> System.out.print("\n" +tri.getcircum());
> System.out.print("\n" +rec.getarea());
> System.out.print("\n" +rec.getcircum());
> }
> }
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