testoverwrite.java

java可以实现一些小程序的编写

class point{
  	int x, y;  
  //	point( ){ this(0,0);System.out.println("point()");}  
  	point(int x, int y){  	  this.x=x;  this.y=y; 
  							  System.out.println("point(x,y)");   }  
  	double  area( ){ return 0; }
} 
class circle extends point{   
	int radius;
    //circle() {System.out.println("circle()");
    //}
   	circle(int r, int x, int y){super(x, y);
   	    System.out.println("\n");    
   	    radius=r;this.x=x;this.y=y;
   	    System.out.println("circle(x,y,r)");   }
   	double  area( ){  return  Math.PI*radius*radius ; } 
} 

public class testOverWrite {
    public static void main(String args[ ]) {
		circle c1;

//先调用子类不带参数的构造方法
//再调用自己带参数的构造方法  
		c1=new circle(1,1,1);  
		System.out.println(c1.area( )); 
	}
}