public class ThreeD extends TwoD {
     private int z;
     
     public ThreeD(int x, int y,int z) {
         super(x, y);
         this.z = z;
     }
     
     public void display() {
         System.out.println("这个空间点的坐标是:"+[color=#FF0000]x[/color]+","+[color=#FF0000]y[/color]+","+z);
     }

public class TwoD {
     private int x;
     private int y;
 
     public TwoD(int x, int y) {
         this.x = x;
         this.y = y;
     }
 
     public int getX() {
         return x;
     }
 
     public void setX(int x) {
         this.x = x;
     }
 
     public int getY() {
         return y;
     }
 
     public void setY(int y) {
         this.y = y;
     }
 
     public void display() {
         System.out.println("这个平面点的坐标是:" + x + "," + y);
     }
}

    public static void main(String[] args) {
             TwoD Tpoint = new TwoD(4, 8);    
             TwoD thpoint = new ThreeD(20,30,40);
             
             show(Tpoint);
             show(thpoint);
             
     }
     
     public static void show(TwoD c){
         c.display();
     }