Double-ended queue (Decue) implementation using Doubly linked list.

package com.java2novice.ds.queue;

public class DequeDblLinkedListImpl<T> {

	private Node<T> front;
	private Node<T> rear;
	
	public void insertFront(T item){
		//add element at the beginning of the queue
		System.out.println("adding at front: "+item);
		Node<T> nd = new Node<T>();
		nd.setValue(item);
		nd.setNext(front);
		if(front != null) front.setPrev(nd);
		if(front == null) rear = nd;
		front = nd;
	}
	
	public void insertRear(T item){
		//add element at the end of the queue
		System.out.println("adding at rear: "+item);
		Node<T> nd = new Node<T>();
		nd.setValue(item);
		nd.setPrev(rear);
		if(rear != null) rear.setNext(nd);
		if(rear == null) front = nd;
		
		rear = nd;
	}
	
	public void removeFront(){
		if(front == null){
			System.out.println("Deque underflow!! unable to remove.");
			return;
		}
		//remove an item from the beginning of the queue
		Node<T> tmpFront = front.getNext();
		if(tmpFront != null) tmpFront.setPrev(null);
		if(tmpFront == null) rear = null;
		System.out.println("removed from front: "+front.getValue());
		front = tmpFront;
	}
	
	public void removeRear(){
		if(rear == null){
			System.out.println("Deque underflow!! unable to remove.");
			return;
		}
		//remove an item from the beginning of the queue
		Node<T> tmpRear = rear.getPrev();
		if(tmpRear != null) tmpRear.setNext(null);
		if(tmpRear == null) front = null;
		System.out.println("removed from rear: "+rear.getValue());
		rear = tmpRear;
	}
	
	public static void main(String a[]){
		DequeDblLinkedListImpl<Integer> deque = new DequeDblLinkedListImpl<Integer>();
		deque.insertFront(34);
		deque.insertFront(67);
		deque.insertFront(29);
		deque.insertFront(765);
		deque.removeFront();
		deque.removeFront();
		deque.removeFront();
		deque.insertRear(43);
		deque.insertRear(83);
		deque.insertRear(84);
		deque.insertRear(546);
		deque.insertRear(356);
		deque.removeRear();
		deque.removeRear();
		deque.removeRear();
		deque.removeRear();
		deque.removeFront();
		deque.removeFront();
		deque.removeFront();
	}
}

class Node<T>{
	
	private Node<T> prev;
	private Node<T> next;
	private T value;
	
	public Node<T> getPrev() {
		return prev;
	}
	public void setPrev(Node<T> prev) {
		this.prev = prev;
	}
	public Node<T> getNext() {
		return next;
	}
	public void setNext(Node<T> next) {
		this.next = next;
	}
	public T getValue() {
		return value;
	}
	public void setValue(T value) {
		this.value = value;
	}
}

adding at front: 34
adding at front: 67
adding at front: 29
adding at front: 765
removed from front: 765
removed from front: 29
removed from front: 67
adding at rear: 43
adding at rear: 83
adding at rear: 84
adding at rear: 546
adding at rear: 356
removed from rear: 356
removed from rear: 546
removed from rear: 84
removed from rear: 83
removed from front: 34
removed from front: 43
Deque underflow!! unable to remove.