DoubleEndedQueue.java

class Queue1 {
    static Node head;
    Node beginning = null;
    Node topOfQueue = null;

    static class Node {

        int data;
        Node next;

        public Node(int data) {
            this.data = data;
            next = null;
        }
    }
        public boolean isEmpty(){
            if(beginning == null && topOfQueue == null)
                return true;
            else return false;

        }
        public  void enqueue(Node newnode){
            if(isEmpty()){
                beginning = newnode;
                topOfQueue = newnode;
            }
        else {
            Node current = head;
            while(current != null){
                current = current.next;
            }
            current.next  = newnode;
            newnode = current;
            topOfQueue = newnode;
        }
        }
        public void enqueueFront(Node newnode){
            if(isEmpty()){
                beginning = newnode;
                topOfQueue = newnode;
            }
            else{
                newnode.next=beginning;
                beginning = newnode;
            }
        }
        public void enqueueRear(Node newnode){
            if(isEmpty()){
                topOfQueue = newnode;
                beginning = newnode;
            }
            else{
                topOfQueue.next = newnode;
                topOfQueue = newnode;
                newnode.next = null;
            }
        }
        public int dequeueFront(){
            int temp = 0;
            if(isEmpty()){
                System.out.println("UnderFlow Condition");
            }
            else {
                 temp = beginning.data;
                beginning = beginning.next;
            }
            return temp;
        }
        public int dequeRear(){
            Node temp = beginning;
            int k = 0;
            if(isEmpty()){
                System.out.println("Underfloww");
            }
            else{
                while(temp.next!=topOfQueue){
                    temp=temp.next;
                }
                k = topOfQueue.data;
                topOfQueue = temp;
                topOfQueue.next =null;
            }
            return k;
        }
    public static void printList(){
        Queue1.Node current = head;
        while(current!=null){
            System.out.println(current.data+" ");
            current=current.next;
        }
    }
    }
public class DoubleEndedQueue {
    public static void main(String[] args) {
        Queue1 obj = new Queue1();
        Queue1.Node obj1 = new Queue1.Node(5);
        Queue1.printList();
    }
}