```java package ds.impl; import ds.Queue; import java.util.Iterator; public class ArrayQueue<T> implements Iterable<T>,Queue<T> { private T[] array; private int size; private int first; private int last; public ArrayQueue() { array = (T[]) new Object[2]; size = 0; first = 0; last = 0; } @Override public int size() { return size; } @Override public void enqueue(T data) { if (size == array.length) { resize(2 * array.length); } array[last++] = data; if (last == array.length) { last = 0; } size++; } @Override public T dequeue() { notEmptyCheck(); T result = array[first]; array[first] = null; size--; first++; if (first == array.length) { first = 0; } if (size > 0 && size == array.length / 4) { resize(array.length / 2); } return result; } @Override public T peek(){ notEmptyCheck(); return array[first]; } private void resize(int capacity) { assert capacity >= size; T[] tmp = (T[]) new Object[capacity]; for (int i = 0; i < size; i++) { tmp[i] = array[(first + i) % array.length]; } array = tmp; first = 0; last = size; } @Override public Iterator<T> iterator() { return new ds.util.ArrayIterator(array,size); } } ```