简单抽象类的应用

abstract class Shape{                                        //定义一个形状的抽象类
 private String color;
 Shape(String c){color=c;}
 abstract double getArea();
 public String toString(){
  return "颜色是"+color;
 }
}
class JuXing extends Shape{                      //定义一个矩形的类继承形状的抽象类
 private double c,k;
 JuXing(String s,double c,double k){
  super(s);                                                  //运用super
  this.c=c;
  this.k=k;
 }
 public double getArea(){
  return c*k;
 }
 public String toString(){                           //算出矩形的面积并返回
  return "这个矩形的面积为"+getArea()+super.toString();
 }}
 class SanJiaoXing extends Shape{         //定义三角形类并继承
  private double d,g;
  SanJiaoXing(String s,double d,double g){
   super(s);
   this.d=d;
   this.g=g;
  }
  public double getArea(){
   return d*g;
  }
  public String toString(){
   return "这个三角形的面积是"+getArea()+super.toString();
  }
 }

public class Di164 {

 public static void main(String[] args) {
  // TODO Auto-generated method stub
  JuXing a=new JuXing("蓝色",2,2);          //初始化矩形
  System.out.println(a.toString());
  SanJiaoXing b=new SanJiaoXing("绿色",2,2);   
  System.out.println(b.toString());

 }

}

程序结果

这个矩形的面积为4.0颜色是蓝色
这个三角形的面积是4.0颜色是绿色