Point p=new Point();
p.print();// x=0,y=0
p.move(100,100);
p.print();//x=100,y=100
p.newPoint("anewpoint").print();//x=-100,y=-100因为newPoint函数中使用了new关键字,重新生成了一个对象,
p.newPoint("anewpoint").print()等价于(p.newPoint("anewpoint")).print()==>x=-100,y=-100