Question

Requirements:   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 ”.

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.
• ==============================================================================
• This is the interface (called PointInterface.Java) 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(

  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(

  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(

  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

PointInterface.java (Interface class)

public interface PointInterface {
@Override
public String toString();
public double distanceTo(Point otherPoint);
@Override
public boolean equals(Object obj);
public boolean inQuadrant(int quadrant);
public void translate(int xMove, int yMove);
public boolean onXAxis();
public boolean onYAxis();
}

Point.java

ublic class Point implements PointInterface{
private int x, y;
  
public Point()
{
this.x = 2;
this.y = -7;
}
  
public Point(int x, int y)
{
this.x = x;
this.y = y;
}
  
public Point(Point p)
{
this.x = p.getX();
this.y = p.getY();
}

public int getX() {
return x;
}

public void setX(int x) {
this.x = x;
}

public int getY() {
return y;
}

public void setY(int y) {
this.y = y;
}
  
@Override
public String toString()
{
return("(" + this.x + "," + this.y + ")");
}

@Override
public double distanceTo(Point otherPoint) {
return Math.hypot((otherPoint.getX() - x), (otherPoint.getY() - y));
}

@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null) {
return false;
}
if (getClass() != obj.getClass()) {
return false;
}
final Point other = (Point) obj;
if (this.x != other.x) {
return false;
}
if (this.y != other.y) {
return false;
}
return true;
}

@Override
public boolean inQuadrant(int quadrant) {
if(quadrant < 1 || quadrant > 4)
throw new IllegalArgumentException("Quadrant out range 1-4");
else
{
boolean inQuadrant = false;
switch(quadrant)
{
case 1:
{
inQuadrant = (x >= 0 && y >= 0);
break;
}
case 2:
{
inQuadrant = (x < 0 && y >= 0);
break;
}
case 3:
{
inQuadrant = (x < 0 && y < 0);
break;
}
case 4:
{
inQuadrant = (x >= 0 && y < 0);
break;
}
}
return inQuadrant;
}
}

@Override
public void translate(int xMove, int yMove) {
this.x = xMove;
this.y = yMove;
}

@Override
public boolean onXAxis() {
return(this.y == 0);
}

@Override
public boolean onYAxis() {
return(this.x == 0);
}
}

PointTest.java (Driver class)

public class PointTest {

public static void main(String[] args) {
  
// creating 3 Point objects
System.out.println("Creating an object of Point using default constructor...");
Point p1 = new Point();
System.out.println("Creating an object of Point using overloaded constructor...");
Point p2 = new Point(0, 9);
System.out.println("Creating an object of Point using copy constructor...");
Point p3 = new Point(new Point(4, 0));

System.out.println("\nDisplaying all the 3 Points...");
System.out.println("Point 1: " + p1.toString());
System.out.println("Point 2: " + p2.toString());
System.out.println("Point 3: " + p3.toString());

System.out.println("\nCalculating distance between the 3 Points...");
System.out.println("Distance between Point 1 and Point 2: " + String.format("%.2f", p1.distanceTo(p2)));
System.out.println("Distance between Point 2 and Point 3: " + String.format("%.2f", p2.distanceTo(p3)));
System.out.println("Distance between Point 3 and Point 1: " + String.format("%.2f", p3.distanceTo(p1)));

System.out.println("\nDetermining onXAxis and onYAxis for all the 3 Points...");
System.out.println("Is Point 1, " + p1.toString() + " on x-axis: " + p1.onXAxis());
System.out.println("Is Point 1, " + p1.toString() + " on y-axis: " + p1.onYAxis());
System.out.println("Is Point 2, " + p2.toString() + " on x-axis: " + p2.onXAxis());
System.out.println("Is Point 2, " + p2.toString() + " on y-axis: " + p2.onYAxis());
System.out.println("Is Point 3, " + p3.toString() + " on x-axis: " + p3.onXAxis());
System.out.println("Is Point 3, " + p3.toString() + " on y-axis: " + p3.onYAxis());

System.out.println("\nDetermining in which quadrant all the 3 Points fall...");
try {
System.out.println("Is Point 1 " + p1.toString() + " in Quadrant 1: " + p1.inQuadrant(1));
System.out.println("Is Point 1 " + p1.toString() + " in Quadrant 2: " + p1.inQuadrant(2));
System.out.println("Is Point 1 " + p1.toString() + " in Quadrant 3: " + p1.inQuadrant(3));
System.out.println("Is Point 1 " + p1.toString() + " in Quadrant 4: " + p1.inQuadrant(4));

System.out.println("\nIs Point 2 " + p2.toString() + " in Quadrant 1: " + p2.inQuadrant(1));
System.out.println("Is Point 2 " + p2.toString() + " in Quadrant 2: " + p2.inQuadrant(2));
System.out.println("Is Point 2 " + p2.toString() + " in Quadrant 3: " + p2.inQuadrant(3));
System.out.println("Is Point 2 " + p2.toString() + " in Quadrant 4: " + p2.inQuadrant(4));

System.out.println("\nIs Point 3 " + p3.toString() + " in Quadrant 1: " + p3.inQuadrant(1));
System.out.println("Is Point 3 " + p3.toString() + " in Quadrant 2: " + p3.inQuadrant(2));
System.out.println("Is Point 3 " + p3.toString() + " in Quadrant 3: " + p3.inQuadrant(3));
System.out.println("Is Point 3 " + p3.toString() + " in Quadrant 4: " + p3.inQuadrant(4));

} catch (IllegalArgumentException iae) {
System.out.println(iae.getMessage());
}

System.out.println("\nTranslating Point 1 to (3,-1), Point 2 to (0, 2) and Point 3 to (8, 0)...");
p1.translate(3, -1);
p2.translate(0, 2);
p3.translate(8, 0);
System.out.println("Point 1: " + p1.toString());
System.out.println("Point 2: " + p2.toString());
System.out.println("Point 3: " + p3.toString());
}
}

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