Question

CS 209 Data Structure

3.

a. Create a class named Point3D that contains 3 instance variables x, y, and z.

b. Create a constructor that sets the variables. Also, create get and set methods for each variable.

c. Create a toString() method.

d. Make Point3D implement Comparable.

Also, create a compareTo(Point3D other) method that compares based on

the x-coordinate, then y-coordinate for tiebreakers, then z-coordinate for tiebreakers.

For example, (1, 2, 5) comes before (2, 1, 4), which comes before (2, 2, 3), which comes before (2, 2, 4).

e. Create a TreeSet of Point3D and insert a few elements including duplicates.

Verify that the TreeSet removes all the duplicates.

Also verify that the TreeSet orders the elements properly.

Answer 1

** Compiled in Eclipse **

CODE:

import java.util.Iterator;
import java.util.TreeSet;

// Class Point3D - implements Comparable interface.
class Point3D implements Comparable<Point3D>
{
        // Class variables.
        int x, y, z;
        
        // Constructor for class Point3D
        public Point3D(int x, int y, int z)
        {
                this.x = x;
                this.y = y;
                this.z = z;
        }
        
        /*
         * compareTo() is used to compare the current object with the specified object. It returns
         * 1, if the current object is greater than the specified object.
     * -1, if the current object is less than the specified object.
     * 0, if the current object is equal to the specified object.
         *
         * Here we will compare x first. If x is greater or lesser than the other object's x, 
         * we will return 1 or -1 respectively.
         * If x is equal, we will compare y. If y is greater or lesser than the other object's y,
         * we will return 1 or -1 respectively.
         * If y is also equal, we will compare z. If it is greater or lesser than the other object's z,
         * we will return 1 or -1 respectively.
         * If z is also equal we will return 1.
         */
        public int compareTo(Point3D obj)
        {
                // (1) x == obj.x -> check y
                if(x == obj.x)
                {
                        // (2) y == obj.y -> check z
                        if(y == obj.y) 
                        {
                                // (3) z == obj.z -> return 1
                                if(z == obj.z)
                                {
                                        return 0;
                                }
                                // (2) z > obj.z -> return 1
                                else if(z > obj.z)
                                {
                                        return 1;
                                }
                                // (2) z < obj.z -> return -1
                                else
                                {
                                        return -1;
                                }
                        }
                        // (2) y > obj.y -> return 1
                        else if(y > obj.y)
                        {
                                return 1;
                        }
                        // (2) y < obj.y -> return -1
                        else
                        {
                                return -1;
                        }
                }
                // (1) x > obj.x -> return 1
                else if(x > obj.x) 
                {
                        return 1;
                }
                // (1) x < obj.x -> return -1
                else
                {
                        return -1;
                }
        }
        
        // toString() return string in the format (x, y, z)
        public String toString()
        {
                return "(" + x + ", " + y + ", " + z + ")";
        }
}

public class testTreeset 
{
        public static void main(String[] args) 
        {
                // Creating object for TreeSet.
                TreeSet<Point3D> ts = new TreeSet<>();  
                // adding the elements to the TreeSet.
                ts.add(new Point3D(1, 2, 5));
                ts.add(new Point3D(2, 2, 3));
                // adding duplicate element.
                ts.add(new Point3D(1, 2, 5));
                ts.add(new Point3D(2, 2, 4));
                ts.add(new Point3D(2, 1, 4));
                
                //Traversing elements using Iterator object. 
                Iterator<Point3D> itr = ts.iterator();  
                while(itr.hasNext())
                {  
                        System.out.println(itr.next());  
                }

        }
}

Screenshots:

refer this to know the proper indentations.

Sample I/O:

The elements in the TreeSet are stored in ascending order without duplicates.

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