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 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 class DoubleEndedQueue {
    public static void main(String[] args) {
        Queue1 quee = new Queue1();
        quee.beginning=new Node(15);

    }
}

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 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;
}
}

class DoubleEndedQueue {
public static void main(String[] args) {
Queue1 quee = new Queue1();
quee.beginning = new Queue1.Node(15);
System.out.println(quee.dequeueFront());

}
}