最近在看《CLR via C#》,有关泛型的优势,感觉说的挺不错的特记录一下,以供以后查看。
泛型为开发人员提供的优势:
为了理解泛型的优势,写了一个程序来比较泛型List算法和FCL的非泛型ArrayList算法的性能。同时使用值类型和引用类型的对象来测试这两个算法的性能: static void Main(string[] args) { ValueTypePerfTest(); ReferenceTypePerfTest(); Console.ReadLine(); } public static void ValueTypePerfTest() { const Int32 count = 10000000; using (new OperationTimer("List<Int32>")) { List<Int32> l = new List<Int32>(count); for (Int32 i = 0; i < count; i++) { l.Add(i); Int32 x = l[i]; } l = null; } using (new OperationTimer("ArrayList of Int32")) { ArrayList a = new ArrayList(); for (Int32 i = 0; i < count; i++) { a.Add(i); Int32 x = (Int32)a[i]; } a = null; } } public static void ReferenceTypePerfTest() { const Int32 count = 10000000; using (new OperationTimer("List<string>")) { List<string> l = new List<string>(); for (Int32 i = 0; i < count; i++) { l.Add("X"); string x = l[i]; } l = null; } using (new OperationTimer("ArrayList of string")) { ArrayList a = new ArrayList(); for (Int32 i = 0; i < count; i++) { a.Add("X"); string x = (String)a[i]; } a = null; } Console.ReadLine(); } } internal sealed class OperationTimer : IDisposable { private Int64 m_startTime; private string m_text; private Int32 m_collectionount; public OperationTimer(string text) { PrepareForOperation(); m_text = text; m_collectionount = GC.CollectionCount(0); m_startTime = Stopwatch.GetTimestamp(); } public void Dispose() { Console.WriteLine("{0,6:###.00} seconds (GCs={1,3}) {2}", (Stopwatch.GetTimestamp()-m_startTime)/(Double)Stopwatch.Frequency, GC.CollectionCount(0)-m_collectionount,m_text); } private static void PrepareForOperation() { GC.Collect(); GC.WaitForPendingFinalizers(); GC.Collect(); }
这个输出结果证明:将泛型list算法应用于Int32类型,速度比将非泛型ArrayList算法应用于Int32快的多,用ArrayList来操作值类型(Int32),会造成大量装箱操作,最终要进行44次垃圾回收次数(GC)。相应地,List算法需要的垃圾回收次数是0。使用引用类型来测试,差别就没有那么明显了。 |
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来自: 昵称10504424 > 《C#》