// The Queue ADT -- linked list implementation

import java.io.*;

public interface LLQueue {

   public void enqueue (int item);
   public int dequeue();
   public int size();
   public boolean empty();
   public int front();

}

class Node {

   private int data;
   private Node next;

   public Node () {
     this(0, null);
   }

   public Node (int d) {
     data = d;
   }
  
   public Node (int d, Node n) {
     data = d;
     next = n;
   }

   public void setData (int newData) {
     data = newData;
   }

   public void setNext (Node newNext) {
     next = newNext;
   } 

   public int getData () {
     return data;
   }

   public Node getNext () {
      return next;
   }

   public void displayNode () {
      System.out.print (data);
   }
}

class LLQueueADT implements LLQueue {

   private int size;
   private Node front;
   private Node rear;

   public LLQueueADT () {
     size = 0;
     front = null;
     rear = null;
   }

   public boolean empty () {
     return (size == 0);
   }

   public void enqueue (int number) {
     Node newNode = new Node ();
     newNode.setData(number);
     newNode.setNext(null);
     if (this.empty()) 
       front = newNode;
     else
       rear.setNext(newNode);
     rear = newNode;
     size++;
   }

   public int dequeue () {
     int i;
     i = front.getData();
     front = front.getNext();
     size--;
     if (this.empty())
        rear = null;
     return i;
   }

   public int front () {
     return front.getData();
   }

   public int size () {
      return size;
   }
}

class LLQueueAppl {

   public static void main (String[] args) throws IOException {

     BufferedReader stdin = new BufferedReader 
            (new InputStreamReader(System.in));
 
     LLQueueADT queue = new LLQueueADT();     

     int i = 2;

     for (int j = 1; j <= 10; j++) {
       queue.enqueue(i); 
       System.out.println (queue.front() + " is the front element.");
       i = i + 2;
     }

     System.out.println ("The current queue contains " + queue.size() +
             " elements.");

     while (!queue.empty())     
        System.out.println (queue.dequeue() + " is dequeued from the queue.");
    
     if (queue.empty()) 
       System.out.println ("The queue is empty.");
     else 
       System.out.println ("There are more elements on the queue.");

   }
}