/*定义一个抽象类draw*/
abstract class draw{
    public abstract void draw();
}
class circle extends draw{
    public void draw(){
        System.out.println("画一个圆形");
    }
}
class retangle extends draw{
    public void draw(){
        System.out.println("画一个矩形");
    }
}
class Main{
    public static void main (String args[]){
        draw d1=new circle();
        draw d2=new retangle();
        d1.draw();
        d2.draw();
    }
}