Array_Queue.java

//Implementation and operations on Queue using Arrays.

import java.util.*;

class arrayQueue
{
    protected int Queue[] ;
    protected int front, rear, size, len;
 
    public arrayQueue(int n) 
    {
        size = n;
        len = 0;
        Queue = new int[size];
        front = -1;
        rear = -1;
    }    

    public boolean isEmpty() 
    {
        return front == -1;
    }    
  
    public boolean isFull() 
    {
        return front==0 && rear == size -1 ;
    }    
 
    public int getSize()
    {
        return len ;
    }    
 
    public int peek() 
    {
        if (isEmpty())
           throw new NoSuchElementException("Underflow Exception");
        return Queue[front];
    }    
    
    public void insert(int i) 
    {
        if (rear == -1) 
        {
            front = 0;
            rear = 0;
            Queue[rear] = i;
        }
        else if (rear + 1 >= size)
            throw new IndexOutOfBoundsException("Overflow Exception");
        else if ( rear + 1 < size)
            Queue[++rear] = i;    
        len++ ;    
    }    

    public int remove() 
    {
        if (isEmpty())
           throw new NoSuchElementException("Underflow Exception");
        else 
        {
            len-- ;
            int ele = Queue[front];
            if ( front == rear) 
            {
                front = -1;
                rear = -1;
            }
            else
                front++;                
            return ele;
        }        
    }

    public void display()
    {
        System.out.print("\nQueue = ");
        if (len == 0)
        {
            System.out.print("Empty\n");
            return ;
        }
        for (int i = front; i <= rear; i++)
            System.out.print(Queue[i]+" ");
        System.out.println();        
    }
}
 
public class Array_Queue
{
    public static void main(String[] args)
    {
        Scanner scan = new Scanner(System.in);
 
        System.out.println("Array Queue Test\n");
        System.out.println("Enter Size of Integer Queue ");
        int n = scan.nextInt();
  
        arrayQueue q = new arrayQueue(n);        
     
        char ch;
        do{
            System.out.println("\nQueue Operations");
            System.out.println("1. Insert");
            System.out.println("2. Remove");
            System.out.println("3. Peek");
            System.out.println("4. Check empty");
            System.out.println("5. Check full");
            System.out.println("6. Size");
            System.out.println("7. Exit");
            int choice = scan.nextInt();
            switch (choice)
            {
            case 1 : 
                System.out.println("Enter integer element to insert");
                try
                {
                    q.insert( scan.nextInt() );
                }
                catch(Exception e)
                {
                    System.out.println("Error : " +e.getMessage());
                }                         
                break;                         
            case 2 : 
                try
                {
                    System.out.println("Removed Element = "+q.remove());
                }
                catch(Exception e)
                {
                    System.out.println("Error : " +e.getMessage());
                }
                break;                         
            case 3 : 
                try
                {
                    System.out.println("Peek Element = "+q.peek());
                }
                catch(Exception e)
                {
                    System.out.println("Error : "+e.getMessage());
                }
                break;                            
            case 4 : 
                System.out.println("Empty status = "+q.isEmpty());
                break;                
            case 5 : 
                System.out.println("Full status = "+q.isFull());
                break;                          
            case 6 : 
                System.out.println("Size = "+ q.getSize());
                break; 
            case 7:
            	System.exit(0);
            	break;
            default : System.out.println("Wrong Entry \n ");
                break;
            }
            scan.close();
            
            q.display();            
            System.out.println("\nDo you want to continue (Type y or n) \n");
            ch = scan.next().charAt(0);
 
        } while (ch == 'Y'|| ch == 'y');                                                        
    }    
}