import java.awt.Point;class ReferenceTest {
    public static void main(String[] arguments){
       Point pt1, pt2;
       pt1=new Point(100,100);
       pt2=pt1;       pt1.x=200;
       pt2.y=200;
       system.out.Println("Point1:"+pt1.x+","+"pt1.y");
       system.out.Println("Point2:"+pt2.x+","+"pt2.y");
     }
}后两行说包system不存在怎么回事