Question

A set is a special kind of list, one that does not allow repeated, or duplicate, entries.

Whenever you must process an item in a data collection only once, you can use a set.

For example, a compiler must find the identifiers in a program and ensure that each one has been defined only once. It could add each identifier encountered to a set. If this addition is unsuccessful, the compiler will have detected an identifier previously found.

Remark: There is no particular ordering of items in set.

IntSet.java file

/** An interface that describes the operations of a set of objects. */

public interface IntSet {

            public int size();

            public boolean isEmpty();

/** Adds a new entry to this set, avoiding duplicates.

@param newEntry The object to be added as a new entry.

@return True if the addition is successful, or

false if the item already is in the set. */

public boolean add(int newEntry);

/** Removes a specific entry from this set, if possible.

@param anEntry The entry to be removed.

@return True if the removal was successful, or false if not. */

public boolean remove(int anEntry);

public void clear();

public boolean contains(int anEntry); // return true if anEntry is currently in the Set

public int[] toArray(); //return all the items currently in the list as an array

public String toString():// returns the content of set as a string

}

Task 1:

Step 1: Create IntSet.java interface and save it as IntSet.java file

Step 2:Imlement IntSet Java interface using an Array. Create ArrayBasedSet.java and complete the following class definition.

public class ArrayBasedSet implements IntSet{

// your implementation details and methods

}

Step 3: Implement Application.java that uses IntSet to perform the following operations in its main method:

            IntSet set1=new ArrayBasedSet();

            set1.add(33);

            set1.add(23);

            set1.add(14);

            set1.add(1);

            set1.add(2);

            set1.add(23);

            set1.add(18);

            set1.add(33);

            set1.add(33);

            set1.add(33);

            System.out.println(set1); //set1.toString is invoked automatically

            if(set1.contains(44))

                        System.out.println(“Set1 contains 44”);

            else

                        System.out.println(“Set1 doesn’ttcontain 44”);

            set1.remove(23);

            System.out.println(set1);

            int []items=set1.toArray();

for(int a:items)

                        System.out.println(a);  

}

Task 2:

Step 1:Create Node.java that contains Node class

Step 2: Create IntSet.java interface and save it as IntSet.java file

Step 3:Imlement IntSet Java interface using Linked Structures. Create LinkedBaseSet.java and complete the following class definition.

public class LinkedBasedSet implements IntSet{

}

Step 4: Implement Application.java that uses IntSet to perform the following operations in its main method:

            IntSet set1=new LinkedBaseSet ();

            set1.add(33);

            set1.add(23);

            set1.add(14);

            set1.add(1);

            set1.add(2);

            set1.add(23);

            set1.add(18);

            set1.add(33);

            set1.add(33);

            set1.add(33);

            System.out.println(set1);//set1.toString is invoked automatically

            if(set1.contains(44))

                        System.out.println(“Set1 contains 44”);

            else

                        System.out.println(“Set1 doesn’ttcontain 44”);

            set1.remove(23);

            System.out.println(set1);

            int []items=set1.toArray();

            for(int a:items)

                        System.out.println(a);

}

Answer 1

File Hierarchy:

/IntSet/IntSet.java

/Node/Node.java

/Application.java

/LinkedBaseSet.java

/ArrayBasedSet.java

IntSet.java:

package IntSet;

public interface IntSet {

            public int size();

            public boolean isEmpty();

       /** Adds a new entry to this set, avoiding duplicates.

       @param newEntry The object to be added as a new entry.

       @return True if the addition is successful, or

       false if the item already is in the set. */

       public boolean add(int newEntry);

       /** Removes a specific entry from this set, if possible.

       @param anEntry The entry to be removed.

       @return True if the removal was successful, or false if not. */

       public boolean remove(int anEntry);//removes the given entry from the list.

       public void clear();//clears the set

       public boolean contains(int anEntry); // return true if anEntry is currently in the Set

       public int[] toArray(); //return all the items currently in the list as an array

       public String toString();// returns the content of set as a string

}

ArrayBasedSet.java:

import IntSet.*;
import java.util.Arrays;

public class ArrayBasedSet implements IntSet{

// your implementation details and methods
   private int[] set;

   ArrayBasedSet()
   {
       //initialize the set array
       set = new int[0];
   }

  
   public int size()
   {
       //return length of set
       return set.length;
   }

   public boolean isEmpty()
   {
       //return true of set is empty and false if not empty
       return (set.length==0);
   }

   public boolean add(int newEntry){

       //returns false if newEntry is already found
       if(contains(newEntry))
       return false;

       //Increments the size of the array
       set = Arrays.copyOf(set,set.length+1);
       //inserts the new value at end of the array
       set[set.length-1]=newEntry;
       return true;
   }

   public boolean remove(int anEntry){
       if(contains(anEntry))
       // if anEntry is found in the set then search for it's index
       for(int i=0;i<set.length;i++)
       {
           if(set[i]==anEntry)
           {
               for(int j=i;j<set.length-1;j++)
               {
                   //deletes the current element by moving all it's succeeders to previous location.
                   set[j]=set[j+1];
               }
               //decrements the size of array.
               set = Arrays.copyOf(set, set.length-1);
               return true;
           }
       }
       //returns false if array doesn't contain the anEntry
       return false;
   }

   public void clear(){
       // clears the set array
       set = new int[0];
   }

   public boolean contains(int anEntry){
       for(int i=0;i<set.length;i++)
       {
           //checks for all values in set and if it is equal to the given anEntry returns true.
           if(set[i]==anEntry) return true;
       }
       //returns flase if not found.
       return false;
   }

   public int[] toArray(){
       //returns the set array as it is.
       return set;
   }

   public String toString(){
       //creates an empty string
       String s=new String();
       for(int i=0;i<set.length;i++)
       {
           //converts each value to string and appends it to existing string.
           s += String.valueOf(set[i])+" ";
       }

       //returns the whole string
       return s;
   }

}

Node.java:

package Node;

//imports LinkedList class from java.util package
import java.util.LinkedList;

public class Node
{
   //creates an empty list.
   public LinkedList<Integer> list;
   public Node()
   {
       //creates new object of the empty list.
       list = new LinkedList<Integer>();
   }
}

LinkedBaseSet.java:

import IntSet.*;
import Node.*;
import java.util.Arrays;

public class LinkedBaseSet implements IntSet{

// your implementation details and methods
   private Node set;

   LinkedBaseSet()
   {
       //creates an empty Node and assigns it to the set.
       set = new Node();
   }

   public int size()
   {
       //return the size of the list in the Node class which is a linked list.
       return set.list.size();
   }

   public boolean isEmpty()
   {
       //return true if the length is 0 i.e., empty. otherwise returns flase.
       return (set.list.size()==0);
   }

   public boolean add(int newEntry){

       if(contains(newEntry))
       //return false if the element is already present in list.
       return false;
       //adds the new entry into the list in the set.
       set.list.add(newEntry);
       return true;
   }

   public boolean remove(int anEntry){
       if(contains(anEntry))
       //return true if the given entry present int he list.
       return set.list.remove(new Integer(anEntry));

       //returns flase otherwise.
       return false;
   }

   public void clear(){
       //clears the list.
       set.list.clear();
   }

   public boolean contains(int anEntry){
       //returns true if the list contains the given entry.
       return set.list.contains(anEntry);
   }

   public int[] toArray(){

       //size for storing the size of the linked list.
       int size = set.list.size();
       //creating an array to store the output.
       int[] arrset = new int[size];
       //storing the object type to Integer array
       Integer[] ret = set.list.toArray(new Integer[size]);
       for (int i = 0; i < size; ++i) {
           //assigning values to the arrset.
           arrset[i] = ret[i];
       }
       //returning the arrset
       return arrset;
   }

   public String toString(){
       //returning the string by converting the data in our list to a string.
       return set.list.toString();
   }

}

Application.java:

import IntSet.*;

public class Application
{
   public static void main(String[] args) {
       System.out.println("ArrayBasedSet");
       IntSet set1=new ArrayBasedSet();

            set1.add(33);

            set1.add(23);

            set1.add(14);

            set1.add(1);

            set1.add(2);

            set1.add(23);

            set1.add(18);

            set1.add(33);

            set1.add(33);

            set1.add(33);

            System.out.println(set1); //set1.toString is invoked automatically

            if(set1.contains(44))

                        System.out.println("Set1 contains 44");

            else

                        System.out.println("Set1 doesn'ttcontain 44");

            set1.remove(23);

            System.out.println(set1);

            int []items=set1.toArray();

           for(int a:items)

                        System.out.println(a);
                       
        System.out.println("LinkedBasedSet");
        IntSet set2=new LinkedBaseSet();

            set2.add(33);

            set2.add(23);

            set2.add(14);

            set2.add(1);

            set2.add(2);

            set2.add(23);

            set2.add(18);

            set2.add(33);

            set2.add(33);
            set2.add(33);

            System.out.println(set2); //set1.toString is invoked automatically

            if(set2.contains(44))

                        System.out.println("Set1 contains 44");

            else

                        System.out.println("Set1 doesn'ttcontain 44");

            set2.remove(23);

            System.out.println(set2);

            int []items1=set2.toArray();

           for(int a:items1)

                        System.out.println(a);
   }                  
}

output:

Hope you got a good idea about what's done.

If you have any doubts please comment in comment section.