分两种情况
①就是队尾rear指针大于队头指针front,length = rear - front
②队尾rear指针小于队头指针front
length1 = 数组长度 - front
length2 = rear
length = length1 + length2 = rear - front + 数组长度
③可以总结出
lenght = (rear - front + 数组长度)% 数组长度
//获取循环队列长度 public int GetLength() { int maxLength = this._maxLength + 1; return (this._rear - this._front + maxLength) % maxLength; }