ArrayList de puntos Aprende programación con ejercicios Java

package Point3D;
import java.util.*;
public class Main
{
	public final static class Point3D
	{
		private double x, y, z;

		public Point3D clone()
		{
			Point3D varCopy = new Point3D();

			varCopy.x = this.x;
			varCopy.y = this.y;

			return varCopy;
		}
	}

	public static void main(String[] args)
	{
		boolean exit = false;

		ArrayList list = new ArrayList();
		Point3D points = new Point3D();

		String answer;
		do
		{
			System.out.println("1. Add data for one point");
			System.out.println("2. Display all the entered points");
			System.out.println("x. Display all the entered points");
			System.out.println();
			System.out.print("Enter a option: ");
			answer = new Scanner(System.in).nextLine();

			if (answer.toLowerCase().equals("x"))
			{
				exit = true;
			}
			else if (answer.equals("1"))
			{
				System.out.print("Point x: ");
				list.add(Integer.parseInt(new Scanner(System.in).nextLine()));

				System.out.print("Point y: ");
				list.add(Integer.parseInt(new Scanner(System.in).nextLine()));

				System.out.print("Point z: ");
				list.add(Integer.parseInt(new Scanner(System.in).nextLine()));
			}
		} while (!exit);
	}
}