How to create a variable name at runtime?

Question

I am not able to create the name of the object at runtime. My statement is:

Map<String,String>  objectName+""+lineNumber = new HashMap<String,String>();

It's giving me compiletime error. I want to create the HashMap object at runtime depending upon the line number.

You can create an Array instead. I don't think what you are trying to achieve is possible! — Shashank Kadne, Oct 18 '12 at 06:48
This is not possible. Can you explain the context of your problem - what are you trying to achieve by doing this? Also, objects don't have names. Variables have names. — Jesper, Oct 18 '12 at 06:48
@Jesper : Possible when generating java source but don't know what user is doing. — Nandkumar Tekale, Oct 18 '12 at 06:50
@Nandkumar Yes, speculation is fun. But information is useful, and here, it must come from the OP. — Andrew Thompson, Oct 18 '12 at 06:53
have you looked into this question http://stackoverflow.com/q/6729605/713414 — Jayy, Oct 18 '12 at 06:54

score 1 · Accepted Answer · answered Oct 18 '12 at 07:00

Java is not a interpreted but rather a compiled language. So the compiler does not knows how to handle this. Such a thing might make sense in a scripting language.

If you need a custom Name for a "variable" maybe a construct like the following might make sense:

Map<String,Map<String,String>> varMap = new HashMap<String,Map<String,String>>();
varMap.put(objectName+" "+lineNumber, new HashMap<String, String>());

score 0 · Answer 2 · answered Oct 18 '12 at 06:57

You can't do this directly in Java (without major tricks)

What you can (and probably should) do:

Put your Map in another map which has the 'variable' name as a key.

If you really want to do that you have to do code generation. For this again you have multiple options:

Generate Java Source Code and compile it
Generate Java Byte Code on the fly. You might wanna look at this list: http://java-source.net/open-source/bytecode-libraries for libraries available.

score -1 · Answer 3 · answered Oct 18 '12 at 06:52

Having a dynamic object name is of No Use.

At first, it's not possible to give reference a dynamic name. The bigger question is Why do you want to do it?

If, just for learning and doing experiments, I'll suggest you should follow proper exercises.

But, if you are trying to achieve some project requirement, Pls. explain the requirement. There will be some other way to achieve that.

How to create a variable name at runtime?

3 Answers3