Data-Structures/CircularQueue.java at master · mchao409/Data-Structures · GitHub

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publicclassCircularQueue<E> {
publicArrayList<E> elements;

/**
 * the index of the front of the CircularQueue
 */
privateintfront;

/**
 * the index of the rear of the CircularQueue
 */
privateintrear;

/**
 * The number of elements currently in the CircularQuue
 */
privateintnumElements;

/**
 * The size of the CircularQueue - maximum number of elements it can hold
 * without resizing
 */
privateintsize;

/**
 * Constructs a CircularQueue with an initial capacity of 10
 */
publicCircularQueue() {
elements = newArrayList<E>();
front = 0; rear = 0; numElements = 0; size = 10;
 }

/**
 * Constructs a CircularQueue with an initial capacity of size num
 * @param num the initial size of the CircularQueue
 */
publicCircularQueue(intnum) {
elements = newArrayList<E>(num);
front = 0; rear = 0; numElements = 0; size = num;
 }

/**
 * Clears the CircularQueue, default size is the same as it was before it
 * was cleared
 */
publicvoidclear() {
elements = newArrayList<E>(size);
front = 0; rear = 0; numElements = 0;
 }

/**
 *
 * @param num the value to check if contained in the CircularQueue
 * @return true, if num is in the CircularQueue, or false, if num is not
 */
publicbooleancontains(Objecte) {
for(inti = 0; i < elements.size(); i++) {
if(e.equals(elements.get(i))) returntrue;
 }
returnfalse;
 }

/**
 *
 * @param arr the array to copy the elements of the CircularQueue
 * over to (shallow copy)
 * @param ind the index to begin copying from
 *
 */
publicvoidcopyTo(E[] arr, intind) {
for(inti = 0; i < elements.size(); i++) {
arr[ind+i] = elements.get(i);
 }
 }

/**
 *
 * @return the element at the front of the CircularQueue
 */
publicEdequeue() {
if(numElements == 0){
thrownewNullPointerException();
 }
Eelement = elements.get(front);
elements.set(front, null);
if(front == size-1) front = 0;
elsefront++;
numElements--;
returnelement;
 }

/**
 *
 * @param element the element to be placed at the rear of the queue
 */
publicvoidenqueue(Eelement){
if(rear < front) {
elements.add(rear, element);
numElements++;
rear++;
return;
 }
elements.add(rear, element);
numElements++;
rear++;
 }

/**
 *
 * @param ind the index of the CircularQueue to retrieve
 * @return the value of the CircularQueue at index ind
 */
publicEget(intind) {
inttempf = front;
intindex = (tempf + ind)% numElements;
returnelements.get(index);
 }

/**
 *
 * @return the element at the front of the CircularQueue, does not remove
 */
publicEpeek() {
if(numElements == 0) {
thrownewNullPointerException();
 }
returnelements.get(front);
 }

publicStringtoString() {
if(front == rear) return"[]";
intstart = front, end = rear;
Stringstr = "" + elements.get(start);
intadd = 0;
if(start > rear) {
start -= elements.size();
add = elements.size();
 }
for(inti = start+1; i < end; i++) {
if(i + add >= size()) {
str += ", " + elements.get(i);
 }
elsestr += ", " + elements.get(i+add);

 }
str = "[" + str + "]";
returnstr;
 }

/**
 *
 * @return the size of the CircularQueue
 */
publicintsize() {
returnsize;
 }
}