Lecture Notes on 6 Aug 2014

class Point
{
  // attributes
  private double x;
  private double y;

  // methods
  // default constructor
  public Point ()
  {
    x = 0.0;
    y = 0.0;
  }

  //non-default constructor
  public Point (double x, double y)
  {
    this.x = x;
    this.y = y;
  }

  // accessors
  public double getX ()
  {
    return this.x;
  }

  public double getY ()
  {
    return this.y;
  }

  // mutators
  public void setX (double x)
  {
    this.x = x;
  }

  public void setY (double y)
  {
    this.y = y;
  }

  // other methods
  // distance to another Point
  public double dist (Point p)
  {
    return Math.sqrt ((this.x - p.x) * (this.x - p.x) +
                      (this.y - p.y) * (this.y - p.y));
  }

  // string representation of a Point
  public String toString ()
  {
    String s = "(" + x + ", " + y + ")";
    return s;
  }

  // check equality of two points
  public boolean equals (Point p)
  {
    double delta = 1.0e-18;
    return (Math.abs(this.x - p.x) < delta) && 
           (Math.abs(this.y - p.y) < delta);
  }

}

public class Geometry
{
  public static void main (String[] args)
  {
    // create a default Point object
    Point p = new Point();

    // set its coordinates
    p.setX(1);
    p.setY(2);

    // create a user defined Point object
    Point q = new Point (5, 8);

    // print out the coordinates of that Point
    System.out.println (q);

    // find the distance between two points
    System.out.println (p.dist(q));
    System.out.println (q.dist(p));
  }
}