C#手写简单的Queue（参考源码）

using System;

namespace DataStructure
{
    public class MyQueue<T>
    {
        private T[] _array;
        private int _head;
        private int _tail;
        private int _size;

        public MyQueue(int capacity)
        {
            if (capacity < 0)
                throw new Exception("默认长度不可小于零");
            this._array = new T[capacity];
            this._head = 0;
            this._tail = 0;
            this._size = 0;
        }

        public int Count
        {
            get { return _size; }
        }

        public bool IsEmpty()
        {
            return _size == 0;
        }

        public void Clear()
        {
            if (this._head < this._tail)
            {
                Array.Clear(this._array, this._head, this._size);
            }
            else
            {
                Array.Clear(this._array, this._head, this._array.Length - this._head);
                Array.Clear(this._array, 0, this._tail);
            }

            this._head = 0;
            this._tail = 0;
            this._size = 0;
        }

        public void Enqueue(T item)
        {
            if (this._size == this._array.Length)
            {
                int capacity = (int) ((long) this._array.Length * 200L / 100L);
                if (capacity < this._array.Length + 4)
                    capacity = this._array.Length + 4;
                this.SetCapacity(capacity);
            }

            this._array[this._tail] = item;
            this._tail = (this._tail + 1) % this._array.Length;
            ++this._size;
        }

        public T Dequeue()
        {
            if (this._size == 0)
                throw new Exception("队列里没有数据了");
            T obj = this._array[this._head];
            this._array[this._head] = default(T);
            this._head = (this._head + 1) % this._array.Length;
            --this._size;
            return obj;
        }

        public T Peek()
        {
            if (this._size == 0)
                throw new Exception("队列里没有数据了");
            return this._array[this._head];
        }

        private void SetCapacity(int capacity)
        {
            T[] objArray = new T[capacity];
            if (this._size > 0)
            {
                if (this._head < this._tail)
                {
                    Array.Copy(this._array, this._head, objArray, 0, this._size);
                }
                else
                {
                    Array.Copy(this._array, this._head, objArray, 0, this._array.Length - this._head);
                    Array.Copy(this._array, 0, objArray, this._array.Length - this._head, this._tail);
                }
            }

            this._array = objArray;
            this._head = 0;
            this._tail = this._size == capacity ? 0 : this._size;
        }

        public bool Contains(T item)
        {
            int index = this._head;
            int size = this._size;
            while (size-- > 0)
            {
                if (item == null)
                {
                    if (this._array[index] == null)
                        return true;
                }
                else if (this._array[index] != null && this._array[index].Equals(item))
                    return true;

                index = (index + 1) % this._array.Length;
            }

            return false;
        }

        public void TrimExcess()
        {
            if (this._size >= (int) ((double) this._array.Length * 0.9))
                return;
            this.SetCapacity(this._size);
        }
    }
}