Java/DataStructures/Queues/Queues.java at master · SetGeek/Java · GitHub

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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
 *
 */
classQueue{
/** Max size of the queue */
privateintmaxSize;
/** The array representing the queue */
privateint[] queueArray;
/** Front of the queue */
privateintfront;
/** Rear of the queue */
privateintrear;
/** How many items are in the queue */
privateintnItems;

/**
 * Constructor
 *
 * @param size Size of the new queue
 */
publicQueue(intsize){
maxSize = size;
queueArray = newint[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
 */
publicbooleaninsert(intx){
if(isFull())
returnfalse;
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++;
returntrue;
	}

/**
 * Remove an element from the front of the queue
 *
 * @return the new front of the queue
 */
publicintremove(){ //Remove an element from the front of the queue
if(isEmpty()){
System.out.println("Queue is empty");
return -1;
 }
inttemp = queueArray[front];
front++;
if(front == maxSize) //Dealing with wrap-around again
front = 0;
nItems--;
returntemp;
	}

/**
 * Checks what's at the front of the queue
 *
 * @return element at the front of the queue
 */
publicintpeekFront(){
returnqueueArray[front];
	}

/**
 * Checks what's at the rear of the queue
 *
 * @return element at the rear of the queue
 */
publicintpeekRear(){
returnqueueArray[rear];
	}

/**
 * Returns true if the queue is empty
 *
 * @return true if the queue is empty
 */
publicbooleanisEmpty(){
return(nItems == 0);
	}

/**
 * Returns true if the queue is full
 *
 * @return true if the queue is full
 */
publicbooleanisFull(){
return(nItems == maxSize);
	}

/**
 * Returns the number of elements in the queue
 *
 * @return number of elements in the queue
 */
publicintgetSize(){
returnnItems;
	}
}

/**
 * This class is the example for the Queue class
 *
 * @author Unknown
 *
 */
publicclassQueues{
/**
 * Main method
 *
 * @param args Command line arguments
 */
publicstaticvoidmain(Stringargs[]){
QueuemyQueue = newQueue(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
	}
}