有关java 写一个父类，他的子类有长方形，三角形，圆解决方法

有关java 写一个父类，他的子类有长方形，三角形，圆
长方形有两个点坐标，三角形中有三个点坐标，圆有圆心和半径，怎么用多态来写，类中的方法有周长和面积

------解决方案--------------------------------------------------------
public class Point{

private long x ;
private long y ;

public Point(long x ,long y){
this.x = x ;
this.y = y ;
}
}

public abstract class Graphics{

public long perimeter() ;
public long area() ;
}

public class Rectangle extends Graphics{
private Point bPoint ;
private Point ePoint ;

public Rectangle(){}
public Rectangle(Point bPoint, Point ePoint){
this.bPoint = bPoint ;
this.ePoint = ePoint ;
}

public long perimeter() {
//自己计算了
}
public long area() {
//自己计算了
}
}

其他类类似 Rectangle

main(String[] args){
Graphics g = new Rectangle(new Point(0, 1), new Point(5,5)) ;
System.out.println(g.area() + "----" + g.perimeter()) ;
}
------解决方案--------------------------------------------------------

探讨

试过了，还有错 bPoint.x对不对
public class Point{

private long x ;
private long y ;

public Point(long x ,long y){
this.x = x ;
this.y = y ;
}
}
class Graphics{

public long perimeter(……