求高人帮我编一个程序

lx17024964

利用多态性编程，创建一个Square类，实现求三角形，正方形和圆形面积。方法：抽象出一个
共享父类，定义一个函数为求面积的公共界面，再重新定义各形状的求面积函数，在主类中创建
不同类的对象，并求得不同形状的面积。

nikia

先帮你顶一下

chengdexy

多态性啊，是不是构造方法那里的啊
搞一个class Square
然后建立3个构造方法
Square（边长1，边长2）{}  //对应长方形
Square(底,高)//对应3角型
Square(半径)//对应圆形


我也初学,大概是这么弄吧

sunnyfun

给楼主一个参考吧：
Shape.java

abstract class Shape {     public abstract void showShape(); }

Square.java

public class Square extends Shape {     public void showShape() {         System.out.print("The Square:");     }     public void calc(long a,long b) {         System.out.println(a * b);     } }

Triangle.java

public class Triangle extends Shape {     public void showShape() {         System.out.print("The Triangle:");     }     public void calc(long a,long b) {         System.out.println(a * b / 2);     } }

Test.java

import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; public class Test {     public static void main(String[] args) {         Shape triangle = new Triangle();         Shape square = new Square(); //        Shape circular = new Circular(); //这个试试自己去实现         Triangle a = new Triangle();         Square b = new Square(); //        Circular c = new Circular(); //这个试试自己去实现         doShowIt(triangle, 2, 4);         doShowIt(square, 2, 4);         // doShowIt(circular, 2); //这个试试自己去实现         System.out.println();         doShowIt(a, 2, 4);         doShowIt(b, 2, 4);         // doShowIt(c, 2); //这个试试自己去实现     }     public static void doShowIt(Shape shape, long a, long b) {// 这里，用抽象类，再来点反射         shape.showShape();                  try {             // 参数值             Object[] value = new Object[] { a, b };                          // 参数类型             Class parm[] = new Class[] { long.class, long.class };                          // 得到类             Class c = shape.getClass();                          // 创建类对象             Object object = c.newInstance();                          // 得到方法对象             Method method = object.getClass().getDeclaredMethod("calc", parm);                          // 调用方法             method.invoke(object, value);         } catch (SecurityException e) {             e.printStackTrace();         } catch (NoSuchMethodException e) {             e.printStackTrace();         }         catch (InstantiationException e) {             e.printStackTrace();         } catch (IllegalAccessException e) {             e.printStackTrace();         } catch (IllegalArgumentException e) {             e.printStackTrace();         } catch (InvocationTargetException e) {             e.printStackTrace();         }     } }