package Queue;

import org.omg.CORBA.Object;

public class CircleQueue<T> implements _Queue<T> {

public T[] arr;

public int size;

public int tail;

public int head;

public static final int DEFAULT = 10;

public CircleQueue() {

this.arr = (T[]) new Object[DEFAULT];

head = tail = 0;

}

public CircleQueue(int capacity) {

this.arr = (T[]) new Object[capacity];

head = tail = 0;

}

/*

环状会有一个unit space 不会被存储内容

cause： 差1 tail == head（队列空）

环状满时，（tail+1）% size = head

*/

public void getLargeQueue(int capacity) {

if (capacity < size)

return;

T[] old = this.arr;

this.arr = (T[]) new Object[capacity];

int j = 0;

//copy the element

for (int i = this.head;i != this.tail; i =(i+1) % old.length) {

arr[j++] = old[i];

}

this.head = 0;

this.tail = j;

}

@Override

public boolean isEmpty() {

return head == tail;

}

@Override

public int size() {

return size;

}

@Override

public boolean add(T data) {

//满环队列。

if (this.head == (this.tail + 1) % this.arr.length ) {

getLargeQueue(arr.length*2);

}

//添加data

arr[this.tail] = data;

this.tail = (this.tail+1) % arr.length;

size++;

return true;

}

@Override

public T peek() {

return arr[head];

}

@Override

public T poll() {

T temp = this.arr[this.head];

this.head = (this.head + 1) % this.arr.length;

size--;

return temp;

}

@Override

public void clear() {

for (int i = this.head ; i != this.tail; i=(i+1)%arr.length) {

arr[i] = null;

}

this.head = this.tail = 0;

size = 0;

}

}