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package rd222dv_assign2.Queues;
import java.util.Iterator;
import java.util.NoSuchElementException;
public class ArrayQueue implements Queue {
private int size = 0;
private Object[] values = new Object[5];
private int first = 0;
private int last = 0;
/* Constructor */
public ArrayQueue() {
}
@Override
public int size() {
return size;
}
@Override
public boolean isEmpty() {
return size == 0;
}
@Override
public void enqueue(Object element) {
/*
* Resize if size is equal to array length. During first time add
* element at position 0, this will be the first and last element of the
* queue. Increase the size. Otherwise, add the element at position size
* and increase the size.
*
*/
if (size == values.length) {
resize();
}
if (isEmpty() == true) { // during first element
values[size] = element;
first = size;
last = first;
} else {
values[size] = element;
last = size;
}
size++;
}
@Override
public Object dequeue() {
/*
* Throw error if array is empty. Otherwise use the private method and
* remove and return the object at position first.
*/
if (isEmpty() == true) {
throw new NoSuchElementException();
}
Object obj = remove();
// shrink(); //will shrink the array and no empty spaces left
return obj;
}
@Override
public Object first() {
/*
* Throw error if array is empty. Otherwise return the object at
* position first.
*/
if (isEmpty() == true) {
throw new NoSuchElementException();
}
return values[first];
}
@Override
public Object last() {
/*
* Throw error if array is empty. Otherwise return the object at
* position last.
*/
if (isEmpty() == true) {
throw new NoSuchElementException();
}
return values[last];
}
@Override
public Iterator iterator() {
return new ArrayQueueIterator();
}
@Override
public String toString() {
StringBuilder str = new StringBuilder();
str.append("[ ");
for (int i = 0; i < size; i++) {
str.append(values[i] + " ");
}
str.append("]");
return str.toString();
}
// double the array
private void resize() {
Object[] temp = new Object[values.length * 2];
for (int i = 0; i < size; i++) {
temp[i] = values[i];
}
values = temp;
}
/*
* First take the first element and save it in a variable, then put rest of
* the element in new array
*/
private Object remove() {
Object[] temp = new Object[values.length];
Object a = values[first];
for (int i = 0; i < size - 1; i++) {
temp[i] = values[i + 1];
}
values = temp;
last = last - 1;
/*
* change the last position, as we shift the second element to position
* first, so we automatically changed the first position.
*/
size--;
return a;
}
/* Iterator */
private class ArrayQueueIterator implements Iterator {
private int total = 0;
@Override
public boolean hasNext() {
return total < size;
}
@Override
public Object next() {
return values[total++];
}
}
public static void main(String[] args) {
Queue arrQueue = new ArrayQueue();
arrQueue.enqueue("cat");
arrQueue.enqueue("turtle");
arrQueue.enqueue("mouse");
arrQueue.enqueue("butterfly");
System.out.println("Is Empty? " + arrQueue.isEmpty());
System.out.println("Current size: " + arrQueue.size());
System.out.println("Current queue: " + arrQueue.toString());
System.out.println("First: " + arrQueue.first());
System.out.println("Last: " + arrQueue.last());
System.out.println("Dequeue: " + arrQueue.dequeue());
System.out.println("Current size: " + arrQueue.size());
System.out.println("Current queue: " + arrQueue.toString());
}
}
/*public static final int MAX = 8; // default capacity of array
private Object[] queue; // has elements of queue
private int capacity; // capacity of array
private int head; // index where the next element will be dequeued
private int tail; // index where the next element will be enqueued
public ArrayQueue() {
this(MAX);
}
public ArrayQueue(int capacity) {
this.capacity = capacity;
this.queue = new Object[capacity];
this.head = 0;
this.tail = 0;
}
@Override
public int size() {
int size = tail - head;
if (size < 0)
size += queue.length;
return size;
}
// return ((capacity - head + tail) % capacity);
// }
@Override
public boolean isEmpty() {
if (size() == 0)
// if (head == -1 && tail == -1) {
return true;
// }
return false;
}
@Override
public void enqueue(Object element) {
if (size() == capacity - 1) {
throw new NoSuchElementException("Array is Full");
} else
queue[tail] = element;
tail = (tail + 1) % capacity;
}
@Override
public Object dequeue() {
if (isEmpty()) {
throw new NoSuchElementException("Array is Empty");
} else if (tail == head) {
Object element = queue[tail];
tail = head = -1;
return element;
} else {
Object element = queue[head];
head = (head + 1) % size();
return element;
}
}
@Override
public Object first() {
if (isEmpty()) {
throw new NoSuchElementException("Array is Empty");
} else {
return queue[head];
}
}
@Override
public Object last() {
if (isEmpty()) {
throw new NoSuchElementException("Array is Empty");
} else {
return queue[tail - 1];
}
}
@Override
public String toString() {
String rep = "";
for (int i = 0; i < size(); i++) {
rep += queue[(head + i) % capacity].toString();
rep += " ";
}
return rep;
}
@Override
public Iterator<Object> iterator() {
Iterator<java.lang.Object> iterator = Arrays.stream(queue).iterator();
return iterator;
}*/
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