为什么要保存在默认情况下，实习生池只包含文字字符串？ [英] Why only literal strings saved in the intern pool by default?

问题描述

为什么默认只有文字字符串保存在实习生池？

从 MSDN 的例子：

 字符串S1 =MyTest的;
。字符串s2 =新的StringBuilder（）追加（我）追加（测试）的ToString（）。
串S3 =的String.intern（S2）;
Console.WriteLine（S1 = ='{0}'，S1）;
Console.WriteLine（S2 = ='{0}'，S2）;
Console.WriteLine（S3 =='{0}'，S3）;
Console.WriteLine（为S2相同的参考为S1？：{0}（对象）S2 = =（对象）S1）;
Console.WriteLine（是S3相同基准为S1？：{0}（对象）S3 ==（对象）S1）;

/ *
该示例产生以下结果：
S1 =='MyTest的
S2 =='MyTest的
S3 =='MyTest的
为S2相同的附图为S1 ?:假
是S3相同的附图为S1？：真
* /
 

解决方案

简短的回答：实习文字字符串是的便宜，运行时和节省内存的。实习非文字字符串是的贵在运行时的，因此节省内存微量换取使得在多数情况下慢得多的。

在实习弦，在运行时优化的成本不支付的利益，因此不是真正的优化。实习文字字符串的成本低廉，因此它支付的利益。

我的回答更详细的问题在这里：

<一个href="http://blogs.msdn.com/b/ericlippert/archive/2009/09/28/string-interning-and-string-empty.aspx">http://blogs.msdn.com/b/ericlippert/archive/2009/09/28/string-interning-and-string-empty.aspx

Why by default only literal strings are saved in the intern pool?

Example from MSDN:

String s1 = "MyTest";
String s2 = new StringBuilder().Append("My").Append("Test").ToString(); 
String s3 = String.Intern(s2); 
Console.WriteLine("s1 == '{0}'", s1);
Console.WriteLine("s2 == '{0}'", s2);
Console.WriteLine("s3 == '{0}'", s3);
Console.WriteLine("Is s2 the same reference as s1?: {0}", (Object)s2==(Object)s1); 
Console.WriteLine("Is s3 the same reference as s1?: {0}", (Object)s3==(Object)s1);

/*
This example produces the following results:
s1 == 'MyTest'
s2 == 'MyTest'
s3 == 'MyTest'
Is s2 the same reference as s1?: False
Is s3 the same reference as s1?: True
*/

解决方案

The short answer: interning literal strings is cheap at runtime and saves memory. Interning non-literal strings is expensive at runtime and therefore saves a tiny amount of memory in exchange for making the common cases much slower.

The cost of the interning-strings-at-runtime "optimization" does not pay for the benefit, and is therefore not actually an optimization. The cost of interning literal strings is cheap and therefore does pay for the benefit.

I answer your question in more detail here:

http://blogs.msdn.com/b/ericlippert/archive/2009/09/28/string-interning-and-string-empty.aspx

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