Question

Follow program instructions carefully. spacing is important. I think It needs a static void main too. Need to run it!

You are to write a class called Point – this will represent a geometric point in a Cartesian plane (but x and y should be ints).   Point should have the following:

Data:  

• that hold the x-value and the y-value. They should be ints and must be private.

Constructors:

• A default constructor that will set the values to (2,-7)

• A parameterized constructor that will receive 2 ints (x then y) and set the data to what is received.

• A copy constructor that will receive a Point. If it receives null, then it should

throw new IllegalArgumentException(<”your meaningful String here”>);

If it is OK, the it should initialize the data (of the new instance being created) to be the same as the Point that was received.

Methods:

• The methods to be implemented are shown in the PointInterface.java. You can look at this file to see the requirements for the methods.

• Your Point class should be defined like this:

public class Point implements PointInterface

When your Point.java compiles, Java will expect all methods in the interface to be implemented and will give a compiler error if they are missing. The compiler error will read “class Point is not abstract and does not implement method <the missing method>”.

You can actually copy the PointInterface methods definitions into your Point class so it will have the comments and the method headers.   If you do this, be sure to take out the ; in the method headers or you will get a “missing method body” syntax error when compiling…

• But…a toString() method and a .equals(Object obj) method are automatically inherited from the Object class. So if you do not implement them, Java will find and use the inherited ones – and will not give a compiler error (but the inherited ones will give the wrong results). The Point class should have its own .toString and .equals methods.

Piece of the code:

//This is the interface for a Point class (which will represent a 2-dimensional Point)

public interface PointInterface
{
   // toString
   //       returns a String representing this instance in the form (x,y) (WITHOUT a space after the ,)
   public String toString();

   // distanceTo
   //       throws a new IllegalArgumentException(<your descriptive String> if null is received
   //       returns the distance from this Point to the Point that was received
   //       NOTE: there is a static method in the Math class called hypot can be useful for this method
   public double distanceTo(Point otherPoint);

   //equals - returns true if it is equal to what is received (as an Object)
   public boolean equals(Object obj);

   // inQuadrant
   //           returns true if this Point is in the quadrant specified
   //           throws a new IllegalArgumentException if the quadrant is out of range (not 1-4)
   public boolean inQuadrant(int quadrant);

   // translate
   //       changes this Point's x and y value by the what is received (thus "translating" it)
   //       returns nothing
   public void translate(int xMove, int yMove);

   // onXAxis
   //       returns true if this Point is on the x-axis
   public boolean onXAxis();

   // onYAxis
   //       returns true if this Point is to the on the y-axis
   public boolean onYAxis();

   //=============================================
   //   The method definitions below are commented out and
   //   do NOT have to be implemented
   //   //=============================================

   // halfwayTo
   //       throws a new IllegalArgumentException(<your descriptive String> if null is received
   //       returns a new Point which is halfway to the Point that is received
   //public Point halfwayTo(Point another);

   // slopeTo
   //       throws a new IllegalArgumentException(<your descriptive String> if null is received
   //       returns the slope between this Point and the one that is received.
   // since the slope is (changeInY/changeInX), then first check to see if changeInX is 0
   //           if so, then return Double.POSITIVE_INFINITY; (since the denominator is 0)
   //public double slopeTo(Point anotherPoint)
}

Answer 1

If you have any doubts, please give me comment...

PointInterface.java

//This is the interface for a Point class (which will represent a 2-dimensional Point)

public interface PointInterface {

    // toString

    // returns a String representing this instance in the form (x,y) (WITHOUT a

    // space after the ,)

    public String toString();

    // distanceTo

    // throws a new IllegalArgumentException(<your descriptive String> if null is

    // received

    // returns the distance from this Point to the Point that was received

    // NOTE: there is a static method in the Math class called hypot can be useful

    // for this method

    public double distanceTo(Point otherPoint);

    // equals - returns true if it is equal to what is received (as an Object)

    public boolean equals(Object obj);

    // inQuadrant

    // returns true if this Point is in the quadrant specified

    // throws a new IllegalArgumentException if the quadrant is out of range (not

    // 1-4)

    public boolean inQuadrant(int quadrant);

    // translate

    // changes this Point's x and y value by the what is received (thus

    // "translating" it)

    // returns nothing

    public void translate(int xMove, int yMove);

    // onXAxis

    // returns true if this Point is on the x-axis

    public boolean onXAxis();

    // onYAxis

    // returns true if this Point is to the on the y-axis

    public boolean onYAxis();

    // =============================================

    // The method definitions below are commented out and

    // do NOT have to be implemented

    // //=============================================

    // halfwayTo

    // throws a new IllegalArgumentException(<your descriptive String> if null is

    // received

    // returns a new Point which is halfway to the Point that is received

    // public Point halfwayTo(Point another);

    // slopeTo

    // throws a new IllegalArgumentException(<your descriptive String> if null is

    // received

    // returns the slope between this Point and the one that is received.

    // since the slope is (changeInY/changeInX), then first check to see if

    // changeInX is 0

    // if so, then return Double.POSITIVE_INFINITY; (since the denominator is 0)

    // public double slopeTo(Point anotherPoint)

}

Point.java

public class Point implements PointInterface {

    private int x;

    private int y;

    public Point(){

        x = 2;

        y = -7;

    }

    public Point(int x, int y){

        this.x = x;

        this.y = y;

    }

    public Point(Point pt){

        if(pt==null)

            throw new IllegalArgumentException("Null pointer exception occured");

        x = pt.x;

        y = pt.y;

    }

    public String toString() {

        return "(" + x + ", " + y + ")";

    }

    // distanceTo

    // throws a new IllegalArgumentException(<your descriptive String> if null is

    // received

    // returns the distance from this Point to the Point that was received

    // NOTE: there is a static method in the Math class called hypot can be useful

    // for this method

    public double distanceTo(Point otherPoint) {

        if (otherPoint == null)

            throw new IllegalArgumentException("Point can't be null");

        return Math.hypot(Math.abs(otherPoint.y - y), Math.abs(otherPoint.x - x));

    }

    // equals - returns true if it is equal to what is received (as an Object)

    public boolean equals(Object obj) {

        Point pt = (Point) obj;

        return pt.x == x && pt.y == y;

    }

    // inQuadrant

    // returns true if this Point is in the quadrant specified

    // throws a new IllegalArgumentException if the quadrant is out of range (not

    // 1-4)

    public boolean inQuadrant(int quadrant) {

        if (quadrant < 1 || quadrant > 4)

            throw new IllegalArgumentException("Quadrant is out of range");

        if ((x > 0 && y > 0 && quadrant == 1) || (x < 0 && y > 0 && quadrant == 2) || (x < 0 && y < 0 && quadrant == 3)

                || (x > 0 && y < 0 && quadrant == 4))

            return true;

        return false;

    }

    // translate

    // changes this Point's x and y value by the what is received (thus

    // "translating" it)

    // returns nothing

    public void translate(int xMove, int yMove) {

        x += xMove;

        y += yMove;

    }

    // onXAxis

    // returns true if this Point is on the x-axis

    public boolean onXAxis() {

        return y == 0;

    }

    // onYAxis

    // returns true if this Point is to the on the y-axis

    public boolean onYAxis() {

        return x == 0;

    }

}

PointTest.java

public class PointTest{

    public static void main(String[] args) {

        Point pt1 = new Point();

        Point pt2 = new Point(3,5);

        System.out.println("Point-1: "+pt1);

        System.out.println("Point-2: "+pt2);

        System.out.println("Distance between Point-1 and Point-2 is: "+pt1.distanceTo(pt2));

        System.out.println("is Point-1 equals to Point-2: "+pt1.equals(pt2));

        System.out.println("is Point-1 in first Quadrant: "+pt1.inQuadrant(1));

        pt1.translate(3,7);

        System.out.println("After translating point-1 with (3,7): "+pt1);

        System.out.println("Is Point-1 on X-axis: "+pt1.onXAxis());

        System.out.println("Is Point-2 on Y-axis: "+pt1.onYAxis());

    }

}