Point(int a, int b) {setPoint(a, b);}public void setPoint(int a, int b) {x=a;y=b;}}class Line extends Point {protected int x, y;Line(int a, int b) {super(a, b);}這樣使用怎么錯了？class Line extends Point {protected int x, y;Line(int a, int b) {x = a;y = b;}