String S = new string ("XYZ"); how many string instances are created?

This is a very interesting and in-depth topic in the ghost broadcaster dotnetw.baodian ().pdf ).pdf.

String S = new string ("XYZ"); how many string instances are created?

The teacher told the students that the answer is two: one is "XYZ" and the other is a reference object pointing to "XYZ.

It seems to be correct. It makes sense. Yes, "XYZ" is a string, and the DOTNET string (in fact, Java is also) has a mechanism such as intern.

Sorry, the teacher of Chuanzhi did not expect that the student or company who asked this question was too bad. The question is wrong, and the answer is wrong.

You can use Visual Studio to create a console.ProgramTry it. Can it be compiled ?!

As for why the answer is not correct, let's take a look at this very detailed explanation, although the author explains it for the Java language.

Http://www.iteye.com/topic/774673

Why can I write in Java like this? Because Java has such ConstructorString(String original) but the string class in DOTNET does not.

Slightly modified to enable compilation

Static void main (string [] ARGs) {char [] chars = {'w', 'O', 'R', 'D '}; string S2 = new string (chars); string S3 = new string (chars); int I = s2.length; Int J = s3.length; console. writeline (I + J );}

 

If we use ilspy, the result is as follows. Note that only newobj is called twice, for S2 and S3 respectively.

. Method private hidebysig static
Void main (
String [] ARGs
) Pencil
Managed
{
// Method begins at RVA 0x2058
// Code size 57
(0x39)
. Maxstack 3
. Entrypoint
. Locals Init (
[0] char []
Chars,
[1] string S2,
[2] string S3,
[3] int32 I,
[4] int32 J
)
Il_0000: LDC. i4.4
Il_0001: newarr [mscorlib] system. Char
Il_0006: DUP
Il_0007: ldtoken
Field
Int64' <privateimplementationdetails> {06fae1c3-0e45-4ae7-a401-b8a7d1eff5d6} ':' $ method0x6000001-1'
Il_000c: Call
Void [mscorlib] system. runtime. compilerservices. runtimehelpers: initializearray (class [mscorlib] system. array, valuetype [mscorlib] system. runtimefieldhandle)
Il_0011: stloc.0

Il_0012: ldloc.0
Il_0013: newobj instance
Void [mscorlib] system. String:. ctor (char [])
Il_0018: stloc.1

Il_0019: ldloc.0
Il_001a: newobj instance
Void [mscorlib] system. String:. ctor (char [])
Il_001f: stloc.2

Il_0020: ldloc.1
Il_0021: callvirt instance
Int32 [mscorlib] system. String: get_length ()
Il_0026: stloc.3

Il_0027: ldloc.2
Il_0028: callvirt instance
Int32 [mscorlib] system. String: get_length ()
Il_002d: stloc. S J

Il_002f: ldloc.3
Il_0030: ldloc. S J
Il_0032: add
Il_0033: Call
Void [mscorlib] system. Console: writeline (int32)
Il_0038: Ret
} // End
Of method program: Main