Thread: Passing An Object To The Constructor Of Another Object

Hello all! This is my first post in this forum, and it's about objects.

I have two separate classes, Point and PlaneCircle. The Point class has two fields, x and y, which are used to construct a coordinate pair on a plane. The PlaneCircle class is supposed to use the coordinates from a Point object, along with a radius, to construct a circle on a plane.

I have code for both Point and PlaneCircle. When trying to create new instances of PlaneCircle using previous instances of Point, I get a NullPointerException error. The code is below.

Point Class

public class Point implements Cloneable{
	public double x, y; 
 
	public Point(double x, double y){ this.x = x; this.y = y; }
 
	public void setX(double x) { this.x = x; }
	public double distanceFromOrigin(){ return Math.sqrt(x*x + y*y); }
}

PlaneCircle

public class PlaneCircle extends Circle {
	Point newPoint; 
 
	public PlaneCircle(Point p, double r){
		super(r); 
		newPoint.x = p.x; 
		newPoint.y = p.y; 
	}
 
	public boolean isInside(double x, double y){
		double dx = x - newPoint.x, dy = y - newPoint.y; 
		double distance = Math.sqrt(dx*dx + dy*dy); 
		return (distance > r); 
	}
}

Main

	public static void main(String[] args) {
 
		Point po1 = new Point(10, 10);
		Point po2 = new Point(11, 11);
		Point po3 = new Point(12, 12);
		Point po4 = new Point(13, 13);
 
		PlaneCircle pcr1 = new PlaneCircle(po1, 11f);
		PlaneCircle pcr2 = new PlaneCircle(po2, 22f);
		PlaneCircle pcr3 = new PlaneCircle(po3, 33f);
		PlaneCircle pcr4 = new PlaneCircle(po4, 44f);

Also, each class is a part of the same package.

Thanks!