Q:

Recursive method works in java with console, but not with android

I wrote a recursive method that gets all possible character combinations from the characters in a string. I also have a method to access it and return a list of the combos:
public static void uns(String word, StringBuilder s, List combos)
{
    for(char c: word.toCharArray())
    {
        s.append(c);
        if(word.length() != 1) 
            {
            uns(removeChar(word, c),s,combos);
            }
        else
        {
            combos.add(s.toString());
        }
        s.deleteCharAt(s.toString().length()-1);
    }

}

public static List getCombinations(String word)
{
    List<String> combinations = new ArrayList<String>();
    uns(word,new StringBuilder(),combinations);
    return combinations;
}

public static String removeChar(String s, char c)
{
    int index = s.indexOf(c);
    return s.substring(0,index)+s.substring(index+1);
}

When testing it in Java, it ran with no flaws. For some reason, when I use it in Android, the list is populated with the correct number of elements, but every element is the same. For instance, for the word "here", it returns a list filled with "eerh".

A:

This is a very weird glitch (definitely reproducible) and you may want to file a bug report on this.
However, here is a temporary workaround; instead of using .toString(), which appears to somehow reuse the reference (even if I do .substring(0) with it), so all of them get updated; if you print out the list after each iteration, you'll see what I mean.
Here is my hacky/inefficient solution. Change:
combos.add(s.toString());

... to:
combos.add(s + "");

This effectively clones the string properly into the array, so that they are not manipulated:

02-17 19:33:48.605: I/System.out(6502): [Combos]: [here, heer, hree, hree, here, heer, ehre, eher, erhe, ereh, eehr, eerh, rhee, rhee, rehe, reeh, rehe, reeh, ehre, eher, erhe, ereh, eehr, eerh]
  

