Question

利用JAVA继承和多态性编写程序:分别利用不同的公式来计算长方形正方形圆的面积

Answer 1

public class Demo { public static void main(String[] args) { A a=new B(); System.out.println(a.re()); a=new C(); System.out.println(a.re()); a=new D(); System.out.println(a.re()); } } abstract class A{ abstract int re(); } class B extends A{ int a=3; int re() { return a*a; } } class C extends B{ int b=4; int re() { return a*b; } } class D extends A{ int r=5; int re() { return (int)Math.PI*r*r; } }