Question

Collect/finish the Java code (interface and the complete working classes) from lecture slides for the for the following ADT:

3) Queue ADT that uses an array internally (call it AQueue)

Make sure you keep the same method names as in the slides (automatic testing will be performed)! Make sure your classes implement the corresponding interfaces. Put your classes in a package called cse11. Try to make the code robust and try to use generics.

The Queue ADT The Queue ADT stores arbitrary objects Auxiliary queue operations: object front(): returns the element at the front without Insertions and deletions follow removing it the first-in first-out (FIFO) integer size(): returns the number of elements stored scheme Insertions are at the rear of the boolean isEmpty(): indicates whether no elements are stored queue and removals are at the front of the queue Exceptions Main queue operations: Attempting the execution of dequeue or front on an empty queue throws an EmptyQueueException enqueue(object): inserts an element at the end of the queue object dequeue(): removes and returns the element at the front Attempting to enqueue an element on a queue that is full can be signaled with a FullQueueException of the queue Queue Interface in Java public interface Queue{ Java interface public int size(); corresponding to our Queue ADT public boolean isEmpty(); public Object front() throws EmptyQueueException; Requires the definition of class public void enqueue(Object o); public Object dequeue() throws EmptyQueueException; EmptyQueueException NB: The java.util.Queue interface uses quite different signatures, and does not insist that the queue be FIFO.

Answer 1

//Queue.java
//Queue interface
public interface Queue
{
   public int size();
   public boolean isEmpty();
   public Object front() throws EmptyQueueException;
   public void enqueue(Object o) throws FullQueueException;
   public Object dequeue() throws EmptyQueueException;
}

//EmptyQueueException.java
class EmptyQueueException extends Exception
{
   public EmptyQueueException(String s)
   {
       super(s);
   }
}

//FullQueueException.java
class FullQueueException extends Exception
{
   public FullQueueException(String s)
   {
       super(s);
   }
}

//AQueue.java
//Implementation of the Queue class
public class AQueue implements Queue
{
   //array of objects
   private Object[] queue;
   //front, rear, capacity and size of the queue
   private int front;
   private int rear;
   private int capacity;
   private int size;
   //constructor with capacity of queue
   AQueue(int length)
   {
       //initialize all data fields
       queue = new Object[length];
       capacity = length;
       front = 0;
       size = 0;
       rear = capacity - 1;
   }
   //function to get size of queue
   public int size()
   {
       return size;
   }
   //function to check queue is empty or not
   public boolean isEmpty()
   {
       return size() == 0;
   }
   //function that returns front value in the queue
   public Object front() throws EmptyQueueException
   {
       if(isEmpty())
       {
           throw new EmptyQueueException("Queue is Empty");
       }
       else
       {
           return queue[front];
       }
   }
   //function to insert in queue
   public void enqueue(Object o) throws FullQueueException
   {
       //if capcity and size are equal then queue is full
       if(capacity == size)
       {
           throw new FullQueueException("Queue is Full");
       }
       else
       {
           //else increment rear value and insert in the queue
           rear = (rear + 1) % capacity;
           queue[rear] = o;
           size ++;
       }
   }
   //function to dequeue from queue
   public Object dequeue() throws EmptyQueueException
   {
       //if queue is empty throw empty queue exception
       if(isEmpty())
       {
           throw new EmptyQueueException("Queue is Empty");
       }
       else
       {
           //or else store the front and incremenet the front index
           Object o = queue[front];
           front = (front + 1) % capacity;
           size --;
           return o;
       }
   }
   //function to print queue
   public void printQueue()
   {
       if(isEmpty())
       {
           System.out.println("Queue is Empty");
       }
       else
       {
           for(int i = front;i<rear+1;i++)
           {
               System.out.print(queue[i]+" ");
           }
           System.out.println();
       }
      
      
   }
}

//Tester.java
class Tester
{
   public static void main(String args[])
   {
       AQueue myQueue = new AQueue(5);
       System.out.println("Before inserting values into Queue:");
       myQueue.printQueue();
       System.out.println("\nEnqueue 3 values into Queue");
       for(int i = 0;i< 13;i++)
       {
           try
           {
               myQueue.enqueue(i);
           }
           catch(FullQueueException e)
           {
               System.out.println("Exception Caught:"+e.getMessage());
           }
       }
       System.out.println("\nAffter Insertion:");
       myQueue.printQueue();
       Object ob;
       System.out.println("\nDequeue 5 values from Queue.It should caught exception");
       for(int i = 0;i<5;i++)
       {
           try
           {
               ob = myQueue.dequeue();
               System.out.println("Value Dequeued from Queue: "+ob);
           }
           catch(EmptyQueueException e)
           {
               System.out.println("Exception Caught:"+e.getMessage());
           }
          
       }
       System.out.println("\nEnqueue 12");
       try
       {
           myQueue.enqueue(12);
       }
       catch(FullQueueException e)
       {
           System.out.println("Exception Caught:"+e.getMessage());
       }
       try
       {
           System.out.println("\nFront in Queue: "+myQueue.front());
       }
       catch(EmptyQueueException e)
       {
           System.out.println("Exception Caught:"+e.getMessage());
       }
   }
}
//sample output

C\Windows\SYSTEM32\cmd.exe c:. Before inserting values into Queue Queue is Empty A Enqueue 3 values into Queue Affter Insertion: C 1 2 Dequeue 5 values f rom Queue.It should caught exception Ualue Dequeued from Queue: 0 Ualue Dequeued from Queue: 1 Ualue Dequeued from Queue: 2 Exception Caught:Queue is Empty Exception Caught:Queue is Empty Enqueue 12 Front in Queue 12 program exited with code: 0) Press any key to continue