Question

JAVA DATA STRUCTURE (Linked Lists/Queue)

public class Node {
   int value;
   Node nextNode;

   Node(int v, Node n){
       value = v;
       nextNode = n;
   }

   Node (int v){
       this(v,null);
   }
}

public class Stack {
   protected Node top;

   Stack(){
       top = null;
   }

   boolean isEmpty(){
       return( top == null);
   }
   void push(int v){
       Node tempPointer;
       tempPointer = new Node(v);
       tempPointer.nextNode = top;
       top = tempPointer;
   }
   int pop(){
       int tempValue;
       tempValue = top.value;
       top = top.nextNode;
       return tempValue;
   }
   void printStack(){
       Node aPointer = top;
       String tempString = "";
       while (aPointer != null)
       {
           tempString = tempString + aPointer.value + "\n";
           aPointer = aPointer.nextNode;
       }

       System.out.println(tempString);
   }
}

public class StackWithLinkedList {
   public static void main(String[] args){
       int popValue;
       Stack myStack = new Stack();
       myStack.push(5);
       myStack.push(7);
       myStack.push(9);
       myStack.printStack();
       popValue = myStack.pop();
       popValue = myStack.pop();
       myStack.printStack();
   }
}

Add the Queue class to the program introduced above. New Class should be CREATED (-->NOT importing<-- ANY TYPE of CLASS from Java Library, just using the provided classes), You should create Queue class like we created the Stack class(see the CODE above). Create the Queue class with the following specifications:

a. It must create a queue(constructor)

b. Insert one end (enqueue)

c. Do extractions at the other end (dequeue)

d. Determine if queue is empty (isEmpty)

e. Print the content of the queue (printQueue)

f. Finally, you must develop a main class QueueWithLinkedList that proves that every method works (just like we did with the StackWithLinkedList class provided in the program above)

Answer 1

Code for Queue is provided below alongwith the output screenshot. Code is Explained in code comments. If need any further clarification please ask in comments.

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CODE-->

//node for storing elemnts 
class Node {
   int value; //to store data
   Node nextNode;  //to store next node
   //constructor
   Node(int v, Node n){
       value = v;
       nextNode = n;
   }
   //constructor
   Node (int v){
       this(v,null);
   }
}
//Queue class
class Queue
{
        protected Node front,rear; //Node as data member
        
        Queue() //constructor
        {
                front=null; //empty Queue has fron and rear null
                rear=null;
        }
        //function to check if Queue is empty
        boolean isEmpty()
        {
                return(front==null); //if yes return true
        }
        //add elemnt in queue
        void enqueue(int value)
        {
                Node tempPointer=new Node(value); //maling node
                
                if(isEmpty()) //checking if Queue ise empty
                {
                        front=rear=tempPointer;  //assigning front=rear a newnode
                        return;
                }
                
                rear.nextNode=tempPointer;  //if there are elemnts in Queue then add this node to the last
                rear=tempPointer;
        }
        //function of deltion of element
        int dequeue()
        {
                Node temp=front;
                if(!isEmpty())  //if Queue is not empty
                {
                        front=front.nextNode;  //set fron of node to next of front node
                }
                
                if(front==null)  //if the Queue has become Empty
                        rear=null;  //then set rear null
                
                return temp.value;  //retrurn popped value
        }
        //function to print Queue
        void printQueue(){
               Node aPointer = front;
               String tempString = "";
               while (aPointer != null)
               {
                   tempString = tempString + aPointer.value + "\n";
                   aPointer = aPointer.nextNode;
               }

               System.out.println(tempString);
           }
}

//main class
public class QueueWithLinkedList {

        public static void main(String[] args) 
        {
                Queue queue=new Queue();  //creating object of Queue
                System.out.println("IS Queue Empty: "+queue.isEmpty());  //checking if empty
                queue.enqueue(5);
                queue.enqueue(10); //adding elements
                queue.enqueue(15);
                queue.enqueue(20);
                queue.enqueue(25);
                queue.enqueue(30);
                System.out.println("After Adding Elements, IS Queue Empty: "+queue.isEmpty());
                System.out.println("Queue is : ");
                queue.printQueue(); 
                System.out.println("Deleteing Element from Queue: "+queue.dequeue());  //deleting element
                System.out.println("Queue After Deletion: ");
                queue.printQueue();  //printing Queue

        }

}

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OUTPUT