Hashtable和Dictionary性能比较

最新推荐文章于 2018-10-19 16:03:49 发布

lele0923

最新推荐文章于 2018-10-19 16:03:49 发布

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本文链接：https://blog.youkuaiyun.com/lele0923/article/details/5517940

本文通过实验比较了在.NET框架中Dictionary与Hashtable两种数据结构在不同数据类型下的性能表现。结果显示，当键为整数时，Dictionary的检索速度远超Hashtable；而键为字符串时，两者性能相近。

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在.net1.1里经常会使用到Hashtable,到里.net 2.0以后我发现有了一个很好用的IDictionary<TKey,TValue>实现类Dictionary<TKey,TValue>。但还是会担心Dictionary<TKey,TValue>的检索效率是否跟Hashtable相当，

据我了解ArrayList的检索效率是非常差的，BinarySearch也不如Hashtable.所以做了一个测试。

class Program { static void Main(string[] args) { IntTest(); StringTest(); IntTryGetValueTest(); Console.WriteLine("========="); IntTest(); StringTest(); IntTryGetValueTest(); Console.ReadLine(); } static void IntTest() { IDictionary<int, int> id = new Dictionary<int, int>(); Hashtable ht = new Hashtable(); int count = 1000000; for (int i = 0; i < count; i++) { id.Add(i, i); ht.Add(i, i); } ////////////// Stopwatch st = Stopwatch.StartNew(); for (int i = 0; i < count; i++) { int str = id[i]; } st.Stop(); Console.WriteLine(string.Format("int类型，Directory:{0}", st.ElapsedMilliseconds)); ////////////// st = Stopwatch.StartNew(); for (int i = 0; i < count; i++) { object obj = ht[i]; } st.Stop(); Console.WriteLine(string.Format("int类型，Hashtable:{0}", st.ElapsedMilliseconds)); } static void StringTest() { IDictionary<string, string> id = new Dictionary<string, string>(); Hashtable ht = new Hashtable(); int count = 1000000; for (int i = 0; i < count; i++) { string str = i.ToString(); id.Add(str, str); ht.Add(str, str); } ////////////// Stopwatch st = Stopwatch.StartNew(); for (int i = 0; i < count; i++) { string i2 = id[i.ToString()]; } st.Stop(); Console.WriteLine(string.Format("string类型，Directory:{0}", st.ElapsedMilliseconds)); ////////////// st = Stopwatch.StartNew(); for (int i = 0; i < count; i++) { object obj = ht[i.ToString()]; } st.Stop(); Console.WriteLine(string.Format("string类型，Hashtable:{0}", st.ElapsedMilliseconds)); } static void IntTryGetValueTest() { IDictionary<int, int> id = new Dictionary<int, int>(); Hashtable ht = new Hashtable(); int count = 1000000; for (int i = 0; i < count; i++) { id.Add(i, i); ht.Add(i, i); } ////////////// Stopwatch st = Stopwatch.StartNew(); for (int i = 0; i < count; i++) { int i2 = 0; id.TryGetValue(i, out i2); } st.Stop(); Console.WriteLine(string.Format("IntTryGetValue，Directory:{0}", st.ElapsedMilliseconds)); ////////////// st = Stopwatch.StartNew(); for (int i = 0; i < count; i++) { object obj = ht[i]; } st.Stop(); Console.WriteLine(string.Format("int类型，Hashtable:{0}", st.ElapsedMilliseconds)); } }

输出为：

int类型，Directory:49
int类型，Hashtable:254
string类型，Directory:1112
string类型，Hashtable:511
IntTryGetValue，Directory:50
int类型，Hashtable:251
=========
int类型，Directory:48
int类型，Hashtable:201
string类型，Directory:944
string类型，Hashtable:505
IntTryGetValue，Directory:51
int类型，Hashtable:167

~~~~~~~~~~~~~~~~~~·

从结果我们可以发现如果key是整数型Dictionary的效率比Hashtable快3到4倍，

如果key是字符串型，Dictionary的效率只有Hashtable的一半。

另外使用TryGetValue对效率没什么影响。