public class Shape {
	
	private double[] coordinates;
	
	public Shape(int numPoints) {
		this.coordinates = new double[numPoints * 3];
	}
	
	public void setPoint(int i, Point point) {
		int j = i * 3;
		coordinates[j + 0] = point.x;
		coordinates[j + 1] = point.y;
		coordinates[j + 2] = point.z;
	}
	
	public Point getCentreOfMass() {
		double xSum = 0.0;
		double ySum = 0.0;
		double zSum = 0.0;
		
		for (int j = 0; j < coordinates.length; j += 3) {
			xSum += coordinates[j + 0];
			ySum += coordinates[j + 1];
			zSum += coordinates[j + 2];
		}
		
		int numPoints = coordinates.length / 3;
		return new Point((xSum / numPoints), (ySum / numPoints), (zSum / numPoints));
	}
	
}