How can I set the name of a variable at runtime in Java?

Question

I want to make the user able to name a String variable at runtime.

Scanner input = new Scanner(System.in);
String name = input.nextLine();

The program asks me to type a word. How can I then create a variable whose identifier is the user's input?

I have tried this:

String (name) = "blah";

But it does not work.

Are you saying to want the variable name to be determined at runtime? That doesn't even make sense, you aren't running the source code. — azurefrog, Oct 07 '14 at 18:19
I'm not sure what are you trying to do, but I think you want to do: `word[1] = "word[2]";` — Konstantin Yovkov, Oct 07 '14 at 18:19
@kocko: it sounds like that if the user writes `blub`, then `word[1]` should be changed to `blub`. And like @azurefrog said, it doesn't make any sense. — Tom, Oct 07 '14 at 18:22
@GeorgeEpicGen java is not interpreted... What's running is the bytecode (the .class files). — Alboz, Oct 07 '14 at 18:22
Right... okay, I think I understand. Thank you for helping though ! — mgthomas99, Oct 07 '14 at 18:30
possible duplicate of [Assigning variables with dynamic names in Java](http://stackoverflow.com/questions/6729605/assigning-variables-with-dynamic-names-in-java) — Dennis Meng, Oct 07 '14 at 20:24

score 2 · Accepted Answer · edited Oct 07 '14 at 18:24

2

You can use a Map

String input1 = ...;
String input2 = ...;
Map m = new HashMap<String,String>();
m.put(input1, input2);

edited Oct 07 '14 at 18:24

Rahul

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answered Oct 07 '14 at 18:21

ControlAltDel

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I was going to suggest this. It feels like Maps are practical for 90% of the things we answer! – Compass Oct 07 '14 at 18:23
Thank you, I will have to try this out as I have never done a map before ... – mgthomas99 Oct 07 '14 at 18:24

score 1 · Answer 2 · answered Oct 07 '14 at 18:22

This does not work in java, cause variable names are "gone" during runtime. The compiled version does no longer use them.

In PHP it is possible, because PHP is interpreted during runtime.

The "closest" you can get is the usage of a hashmap:

Map<String,String> kvps = new HashMap<String,String>();
kvps.put ("varname", "varvalue");
kvps.put ("hello", "world");
kvps.put ("foo", "bar");

for (Map.Entry<String, String> kvp: kvps.getEntrySet()){
  System.out.println(kvp.getKey() + " = " + kvp.getValue());
}

score 0 · Answer 3 · edited Oct 27 '17 at 09:16

0

There is a way you can get a name of a variable - if it is a field of a class, then you can use reflection:

Field[] classFields = classInstance.getDeclaredFields();

Now you can get the field names:

classFields[index].getName();

edited Oct 27 '17 at 09:16

mgthomas99

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answered Oct 07 '14 at 18:35

user265732

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How can I set the name of a variable at runtime in Java?

3 Answers3