Question

Is it possible to set a variable, if i want to have it flexible? I think an exmaple makes it easier to understand.

String hallo1;
String hallo2;

for(int i = 0; i < 2; i++) {
 hallo & i = Integer.toString(i);
}

Answer 1

If you really have a need to have variables with names not known at compile time, you can achieve this effect by creating a structure that holds arbitrary names and values. Like, you could create a HashMap where the key is the name. Then your example above becomes something like:

  HashMap myData=new HashMap();
  for (int i=0;i<2;++i)
  {
    myData.put("hallo"+i,Integer.toString(i));
  }

Later you’d pull them out with:

  String whatever=myData.get("hallo1");

etc.

Of course you can’t access values from the map as variables directly, you’d always have to do put and get to update and retrieve them, but the concept is the same.

That said, I’d be very cautious about doing this, because it makes the code difficult to maintain. If the names that you need are really coming out of the blue — if you’re writing generic code to read an arbitrary database table whose name was typed in by the user at runtime or something like that — cool. But if you’re thinking that this is a handy shortcut for something like:

  if (region.equals("1"))
    region1Total+=amount;
  else
    region2Total+=amount;

My simple answer would be DON’T!! The code is much easier to maintain if you use the IF statement and normal variables. Then anyone reading the code can look at your declarations and see what all the possible variables are. You can do text searches to find everywhere they’re used. If you mis-spell a variable name, instead of magically creating a new variable you will get a clean compile-time error message. Etc.

On the other hand, if you COULD write something like

  String n=getInputFromScreen();
  String s=getAnotherInputFromScreen();
  hallo & n = s;

you would have no idea what variables exist in your program and no way to track where they are used.