Point2D.java

package org.drip.zen.geometry;

/*
 * 1) Motivation behind Class - Structure and Function
 * 2) x/y fields and printing them
 * 3) Invocation of the Class - Creation of the Class Instance
 * 4) Adding a method - set to Origin
 * 5) Add the Constructor with fields
 * 6) Member Fields with an underscore
 * 7) Distance from Origin
 * 8) Angle with X axis at Origin
 * 9) Degrees to Radians Conversion
 * 10) Quadrant
 * 11) Degrees to Radian with the Qudrant Assignment
 * 12) Distance From Another Point
 * 13) Translate the Points - 20 March 2016 #2
 * 14) Polar Coordinate Representation - 20 March 2016 #3
 * 15) Sketch the Problem Solution - 20 March 2016 #4
 * 16) Point from Polar Coordinates - 20 March 2016 #5
 * 17) Introducing the static Constructor - 20 March 2016 #6
 */

public class Point2D {
    private double _x = -1.;
    private double _y = -1.;

    /*
     * Added 20 March 2016
     */

    public static Point2D MakeFromPolar (double r, double angle)
    {
        double x = r * Math.cos (angle);

        double y = r * Math.sin (angle);

        Point2D p = new Point2D (x, y);

        return p;
    }

    /*
     * Done Adding 20 March 2016
     */

    Point2D (double x, double y)
    {
        _x = x;
        _y = y;
    }

    public double getX()
    {
        return _x;
    }

    public double getY()
    {
        return _y;
    }

    void printCoordinate()
    {
        System.out.println ("\t[" + _x + ", " + _y + "]");
    }

    void resetToOrigin()
    {
        _x = 0.;
        _y = 0.;
    }

    double distanceFromOrigin()
    {
        double distance = Math.sqrt (_x * _x + _y * _y);

        return distance;
    }

    double distanceBetweenPoints (Point2D anotherPoint)
    {
        double x1 = _x;
        double y1 = _y;
        double x2 = anotherPoint._x;
        double y2 = anotherPoint._y;

        double distance = Math.sqrt ((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));

        return distance;
    }

    public double angleAtOrigin()
    {
        double adjustedAngleAtOrigin = 0.;
        double angleAtOriginTan = _y / _x;

        double unadjustedAngleAtOrigin = Math.atan (angleAtOriginTan);

        if (_x > 0 && _y > 0)
            adjustedAngleAtOrigin = unadjustedAngleAtOrigin;
        else if (_x < 0 && _y > 0)
            adjustedAngleAtOrigin = unadjustedAngleAtOrigin + Math.PI;
        else if (_x < 0 && _y < 0)
            adjustedAngleAtOrigin = unadjustedAngleAtOrigin + Math.PI;
        else if (_x > 0 && _y < 0)
            adjustedAngleAtOrigin = unadjustedAngleAtOrigin + 2. * Math.PI;
        else if (_x > 0 && _y < 0)
            adjustedAngleAtOrigin = 0.;

        return adjustedAngleAtOrigin * 180. / Math.PI;
    }

    String quadrant()
    {
        String region;

        if (_x > 0 && _y > 0)
            region = "UPPER RIGHT";
        else if (_x < 0 && _y > 0)
            region = "UPPER LEFT";
        else if (_x < 0 && _y < 0)
            region = "LOWER LEFT";
        else if (_x > 0 && _y < 0)
            region = "LOWER RIGHT";
        else
            region = "ORIGIN";

        return region;
    }

    /*
     * Added 20 March 2016
     */

    public boolean translate (double xShift, double yShift)
    {
        _x = _x + xShift;
        _y = _y + yShift;
        return true;
    }

    void printPolarCoordinate()
    {
        System.out.println ("\t[" + distanceFromOrigin() + ", " + angleAtOrigin() + "]");
    }

    /*
     * Done Adding On 20 March 2016
     */

    public static void main (String[] args)
    {
        Point2D myPoint = new Point2D (2., 3.);

        myPoint.printCoordinate();

        myPoint._x = 1;
        myPoint._y = 1;

        myPoint.printCoordinate();

        myPoint.resetToOrigin();

        myPoint.printCoordinate();

        System.out.println ("\tDistance From Origin: " + myPoint.distanceFromOrigin());

        Point2D secondPoint = new Point2D (3., 4.);

        System.out.println ("\tDistance Between Points: " + myPoint.distanceBetweenPoints (secondPoint));

        myPoint._x = 2;
        myPoint._y = -2;

        System.out.println ("\tAngle at Origin: " + myPoint.angleAtOrigin());

        System.out.println ("\tQuadrant: " + myPoint.quadrant());
    }
}