Dequeue (Double Ended Queue) using Arrays ADT

Double Ended Queue :

Program :

package adsa;

import java.util.Scanner;
interface DQArrADT{
    void linsert();
    void rinsert();
    void ldelete();
    void rdelete();
    void display();
}
public class DQArr implements DQArrADT{
    int dq[],size,front,rear;
    Scanner s=new Scanner(System.in);
    
    public DQArr() throws Exception
    {
        System.out.println("Enter the Deque size");
        size=s.nextInt();
        dq=new int[size];
        front=-1;rear=-1;
    }
    
    public void linsert()
    {
        if(((front==0)&&(rear==dq.length-1))||(rear==front-1))
            System.out.println("Deque is full");
        else if(front==-1)
        {
            front=0;
            rear=0;
        }
        else if(front==0)
            front=(dq.length-1);
        else
            front=front-1;
        System.out.println("Enter the element into deque at left end :");
        int item=s.nextInt();
        dq[front]=item;
    }
    
    public void rinsert()
    {
        if(((front==0)&&rear==dq.length-1)||(rear==front-1))
            System.out.println("Deque is full");
        else if(front==-1)
        {   
            front=0;
            rear=0;
        }
        else if(rear==dq.length-1){
            rear=0;
            System.out.println("rear is changed to "+rear);}
        else
            rear=rear+1;
        
        System.out.println("Enter the element into the Deque at right end :");
        int item=s.nextInt();
        dq[rear]=item;
    }
    
    public void ldelete()
    {
        if(front==-1)
            System.out.println("Deque underflow");
        else
        {
            System.out.println("Deleted item at leftend is :"+dq[front]);
            if(front==rear)//one element
            {
                front=-1;rear=-1;
            }
            else if(front==dq.length-1)
                front=0;
            else front=front+1;
        }
    }
    public void rdelete(){
        if(front==-1)System.out.println("Deque underflow");
        else
        {
            System.out.println("Deleted item at right end :"+dq[rear]);
            if(front==rear){//one element
                front=-1;rear=-1;
            }
            else if(rear==0){
                rear=dq.length-1;
            }
            else rear=rear-1;
        }
    }
    
    
    public void display()
    {
        if(front==-1)
            System.out.println("Deque empty");
        System.out.println("Deque elements are:");
        if(front<=rear)
        {
            for(int i=front;i<=rear;i++)
                System.out.print(" "+dq[i]);
        }
        else{
            for(int i=front;i<dq.length;i++)
                System.out.print(" "+dq[i]);
            for(int i=0;i<=rear;i++)
                System.out.print(" "+dq[i]);
        }
    }
    
    public static void main(String args[]) throws Exception{
        System.out.println("Linear Dequeu Array ADT");
        Scanner s=new Scanner(System.in);
        DQArr d=new DQArr();
        String ch="y";
        while(ch.equalsIgnoreCase("y")){
            System.out.println("Deque operations :");
            System.out.println("1. DQ LInsert 2. DQ RInsert 3. DQ LDelete 4. DQ RDelete 5. Display 6.Exit :");
            System.out.println("Enter the option :");
            int opt=s.nextInt();
            switch(opt){
                case 1: d.linsert();
                        break;
                case 2:d.rinsert();
                        break;
                case 3:d.ldelete();
                        break;
                case 4:d.rdelete();
                        break;
                case 5:d.display();
                        break;
                case 6:System.exit(0);
                default:System.out.println("Invalid option!!!");
            }
            System.out.println("Do you want to continue(y/N) :");
            ch=s.next();
        }
    }
}