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/**

* This implements Queues by using the class Queue.

*

* A queue data structure functions the same as a real world queue.

* The elements that are added first are the first to be removed.

* New elements are added to the back/rear of the queue.

*

* @author Unknown

*

*/

class Queue{

/** Max size of the queue */

private int maxSize;

/** The array representing the queue */

private int[] queueArray;

/** Front of the queue */

private int front;

/** Rear of the queue */

private int rear;

/** How many items are in the queue */

private int nItems;

/**

* Constructor

*

* @param size Size of the new queue

*/

public Queue(int size){

maxSize = size;

queueArray = new int[size];

front = 0;

rear = -1;

nItems = 0;

}

/**

* Inserts an element at the rear of the queue

*

* @param x element to be added

* @return True if the element was added successfully

*/

public boolean insert(int x){

if(isFull())

return false;

if(rear == maxSize-1) //If the back of the queue is the end of the array wrap around to the front

rear = -1;

rear++;

queueArray[rear] = x;

nItems++;

return true;

}

/**

* Remove an element from the front of the queue

*

* @return the new front of the queue

*/

public int remove(){ //Remove an element from the front of the queue

if(isEmpty()){

System.out.println("Queue is empty");

return -1;

}

int temp = queueArray[front];

front++;

if(front == maxSize) //Dealing with wrap-around again

front = 0;

nItems--;

return temp;

}

/**

* Checks what's at the front of the queue

*

* @return element at the front of the queue

*/

public int peekFront(){

return queueArray[front];

}

/**

* Checks what's at the rear of the queue

*

* @return element at the rear of the queue

*/

public int peekRear(){

return queueArray[rear];

}

/**

* Returns true if the queue is empty

*

* @return true if the queue is empty

*/

public boolean isEmpty(){

return(nItems == 0);

}

/**

* Returns true if the queue is full

*

* @return true if the queue is full

*/

public boolean isFull(){

return(nItems == maxSize);

}

/**

* Returns the number of elements in the queue

*

* @return number of elements in the queue

*/

public int getSize(){

return nItems;

}

}

/**

* This class is the example for the Queue class

*

* @author Unknown

*

*/

public class Queues{

/**

* Main method

*

* @param args Command line arguments

*/

public static void main(String args[]){

Queue myQueue = new Queue(4);

myQueue.insert(10);

myQueue.insert(2);

myQueue.insert(5);

myQueue.insert(3);

//[10(front), 2, 5, 3(rear)]

System.out.println(myQueue.isFull()); //Will print true

myQueue.remove(); //Will make 2 the new front, making 10 no longer part of the queue

//[10, 2(front), 5, 3(rear)]

myQueue.insert(7); //Insert 7 at the rear which will be index 0 because of wrap around

// [7(rear), 2(front), 5, 3]

System.out.println(myQueue.peekFront()); //Will print 2

System.out.println(myQueue.peekRear()); //Will print 7

}

}