package Queue;

/*
 @author: Roderland
 @create: 2020年08月11日---18:17
*/
public class MyArrayQueue<E> {

 private static final int DEFAULT_CAPACITY = 10;

 private E[] array;

 private int head;

 private int limit;

 public MyArrayQueue() {
 array = (E[]) new Object[DEFAULT_CAPACITY];
 }

 public MyArrayQueue(int capacity) {
 array = (E[]) new Object[capacity];
 }

 public void push(E o) {
 if (isOutOfLength()) expansion();
 array[limit++] = o;
 }

 public E peek() {
 if (isEmpty()) throw new IndexOutOfBoundsException("队列空");
 return array[head];
 }

 public E pop() {
 if (isEmpty()) throw new IndexOutOfBoundsException("队列空");
 return array[head++];
 }

 public boolean isOutOfLength() {
 return limit >= array.length;
 }

 public boolean isEmpty() {
 return head >= limit;
 }

 public void expansion() {
 E[] newArray = (E[]) new Object[(limit - head) * 2];
 for (int i = head, j = 0; i < limit; i++, j++) {
 newArray[j] = array[i];
 }
 array = newArray;
 limit = limit - head;
 head = 0;
 }
}