01.线性表 ArrayList

   public class MyArrayList
     {
         //容量
         private const int _defaultCapacity = ;
         //存放数组元素
         private object[] _items;
         //数组大小
         private int _size;
         //元素个数为0的数组状态
         private static readonly object[] emptyArray = new object[];

         public MyArrayList()
         {
             this._items = emptyArray;
         }

         public MyArrayList( int capacity)
         {
             if (capacity<)
             {
                 throw new ArgumentOutOfRangeException("capacity","ArrayList的容量不可为负数！");
             }
             this._items = new object[capacity];
         }

         //索引器
         public virtual object this[int index]
         {
             get
             {
                 if (index<||index>=this._size)
                 {
                     throw new ArgumentOutOfRangeException("index","索引超出范围！");
                 }
                 return this._items[index];
             }

             set
             {
                 if (index <  || index >= this._size)
                 {
                     throw new ArgumentOutOfRangeException("index", "索引超出范围！");
                 }
                 this._items[index] = value;
             }

         }

         //当前数组元素个数
         public virtual int Count
         {
             get {return this._size ;}
         }

         //数组的容量
         public virtual int Capacity
         {
             get { return this._items.Length; }
             set
             {
                 if (value!=this._items.Length)
                 {
                     if (value<this._size)
                     {
                         throw new ArgumentOutOfRangeException("value","容量太小");
                     }
                     if (value > )
                     {//开辟新内存空间存储元素
                         object[] dest = new object[value];
                         if (this._size > )
                         {//搬动元素
                             Array.Copy(this._items, , dest, , this._size);
                         }
                         this._items = dest;
                     }
                     else//数组最小的空间为4
                     {
                         this._items=new object[_defaultCapacity];
                     }
                 }
             }
         }

         //元素的添加
         public virtual int Add(object value)
         {//当空间已满
             if (this._size==this._items.Length)
             {
                 this.EnsureCapacity(this._size+);
             }
             this._items[this._size] = value;
             return this._size++;
         }

         //扩容
         private void EnsureCapacity(int p)
         {
             if (this._items.Length<p)
             {//空间加倍
                 int num = (this._items.Length == ) ? _defaultCapacity : (this._items.Length * );
                 if (num < p)
                 {
                     num = p;
                 }
                 this.Capacity = num;
             }
         }

         //指定位置插入元素
         public virtual void Insert( int index,object value)
         {
             if (index<||index>this._size)
             {
                 throw new ArgumentOutOfRangeException("index","索引超出范围！");
             }
             if (this._size==this._items.Length)
             {
                 this.EnsureCapacity(this._size + );
             }
             if (index<this._size)
             {
                 Array.Copy(this._items, index, this._items, index + , this._size - index);
             }
             this._items[index] = value;
             this._size++;
         } 

         //移除指定索引的元素
         public virtual void Remove(int index)
         {
             if (index <  || index > this._size)
             {
                 throw new ArgumentOutOfRangeException("index", "索引超出范围！");
             }
             this._size--;
             if (index<this._size)
             {
                 Array.Copy(this._items,index+,this._items,index,this._size-index);
             }
             this._items[this._size]=null;
         }

         //裁剪空间
         public virtual void TrimToSize()
         {
             this.Capacity = this._size;
         }
     }