请大佬看下为什么代码的测试类里不能直接使用多态？
/*这是子类——圆类*/
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | package com.imooc;import java.util.Scanner;public class Circle extends Shape {Scanner in = new Scanner(System.in);public void call(){System.out.println("现在是计算圆的面积和周长");System.out.println("请输入圆的半径");double r=in.nextDouble();double Pi=3.14;System.out.println("圆的面积："+Square(r,Pi));System.out.println("圆的周长："+Leng(r,Pi));}public double Square(double a, double b) {// TODO Auto-generated method stubdouble S;S=b*a*a;return S;}public double Leng(double a, double b) {// TODO Auto-generated method stubdouble l;l=b*2*a;return l;}} |
/*这是子类——矩形类*/
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 | package com.imooc;import java.util.Scanner;public class Rectangle extends Shape {Scanner in = new Scanner(System.in);public void call() {System.out.println("计算矩形的周长和面积");System.out.println("请输入两条边长");double a = in.nextDouble();double b = in.nextDouble();System.out.println("矩形的面积是："+Square(a,b));System.out.println("矩形的周长是："+Leng(a,b));}@Overridepublic double Square(double a, double b) {// TODO Auto-generated method stubdouble S;S=a*b;return S;}@Overridepublic double Leng(double a, double b) {// TODO Auto-generated method stubdouble l;l=2*(a+b);return l;}} |
/*这是父类*/
1 2 3 4 5 | package com.imooc;public abstract class Shape {public abstract double Square(double a,double b);public abstract double Leng(double a,double b);} |
/*这是测试类*/
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | package com.imooc;public class Initial {public static void main(String[] args) {/*Rectangle rec = new Rectangle();rec.call();Circle cir = new Circle();cir.call();*///以上方法是可行的Shape rec = new Rectangle();((Rectangle) rec).call();Shape cir = new Circle();((Circle) cir).call();}//这个方法也是可行的} |
我主要是想知道为什么以下内容会报错，必须改成上面那两种才可以
1 2 3 4 | Shape rec = new Rectangle();rec.call();Shape cir = new Circle();cir.call() |
