Comparing Collection object with a string

Question

Hi everyone,
There is my problem: I have a program that generate all possible combinations of a certain number of letters for example: -ABC- will gives A, B, C, AB, AC, BC, ABC. Everything is fine at this point. But then the user can input a string like "AB" and I have to tell him if this string is contained in the generated set. My set is in a Collection, but when I used : LetterCombination.Contains(TextString), it returns always false. Even if I know that the string is contained in the set.
Here is the code to generate the set:
public class Recursion
     Collection LetterCombination;
/*String Letters is the letters which I have to generate the combination, and
the LetterNumber is the number of letters contained in my string.*/
     public Recursion(Set ItemLetters, String Letters, int LetterNumbers)
          ItemLetters = new TreeSet();
String[] Token = Letters.split(" ");
/*Adding the letters in the TreeSet*/
for (int i = 0; i < LetterNumbers; i++)
     ItemLetters.add(Token);
LetterCombination = BuildLetterSet(ItemLetters);
private Collection BuildLetterSet(Set ItemLetters)
Set NotUsedYet = new TreeSet();
Set thisPowerSet = new TreeSet();
Collection Letterresult = new ArrayList();
NotUsedYet.addAll(ItemLetters);
BuildByRecursion(NotUsedYet, thisPowerSet, Letterresult);
return Letterresult;
private void BuildByRecursion(Set notUsedYet, Set thisPowerSet, Collection result)
if(notUsedYet.isEmpty())
if(!thisPowerSet.isEmpty())
Set copy = new TreeSet();
copy.addAll(thisPowerSet);
result.add(copy);
return;
Object item = notUsedYet.iterator().next();
notUsedYet.remove(item);
BuildByRecursion(notUsedYet, thisPowerSet, result);
thisPowerSet.add(item);
BuildByRecursion(notUsedYet, thisPowerSet, result);
thisPowerSet.remove(item);
notUsedYet.add(item);
And if I print out the LetterCombination collection, it gives me:
[C]
[B, C]
[A]
[A, C]
[A, B]
[A, B, C]
Which are the good combination needed. But I really don't understand how to compare this collection with the string entered by the user.
I'm really lost. can somebody help me! Thanks in advance...

Answer 1

You don't show where you call this constructor, or what your arguments are:
public Recursion(Set ItemLetters, String Letters, int LetterNumbers)
   ItemLetters = new TreeSet();
   String[] Token = Letters.split(" ");
   /*Adding the letters in the TreeSet*/
   for (int i = 0; i < LetterNumbers; i++)
      ItemLetters.add(Token[ i ]);
   LetterCombination = BuildLetterSet(ItemLetters);
}But, the constructor doesn't make sense, anyway. itemLetters is immediately set to a new TreeSet, so whatever you passed in (if anything) for the first argument is unchanged by the constructor (and the new TreeSet is lost when you finish the constructor). Also, you split your input Letters on space, but rely on LetterNumbers for the length of the split array (which may or may not be accurate). Why not do a 'for' loop testing for "i < Token.length", and eliminate LetterNumbers parameter? Your input for the second parameter to this constructor would have to be "A B C D" (some letters delimited by spaces). Your constructor only needs one parameter--that String.
The capitalization of your variables doesn't follow standard coding conventions. Your code is hard to read without the "code" formatting tags (see "Formatting Tips"/ [ code ] button above message posting box).