Question

I am having problems with creating HashTable in my program, I am creating WordLadder game.
Basically I want my HashTable to contain key which is unique word and value would be words which are one letter difference. Problem is that when I print out to check what I am putting into it, it prints perfectly what I want, however when I return HashTable it returns me nonsense.

My code for generating HashTable is following:

public Hashtable<String, ArrayList<String>> findNeighbors(){
      Hashtable<String, ArrayList<String>> data = new Hashtable<String, ArrayList<String>>();
      ArrayList<String> neighb = new ArrayList<String>();
      for(int i=0; i < 5; i++){
       for(int j=0; j < 5; j++){
        if (isNeighbor(words.get(i), words.get(j))) {
         neighb.add(words.get(j));
        }
       }
       data.put(words.get(i), neighb);
       //System.out.println(words.get(i)+ " "+data.get(words.get(i))); <This Works perfectly fine
       System.out.println(data.toString()); //<This returns nonsense
       neighb.clear();
      }

      return data;
     }

public boolean isNeighbor(String a, String b){
      int diff = 0;
      for (int i = 0; i < a.length(); i++){
       if(a.charAt(i) != b.charAt(i)){
        diff++;
       }
      }
      return diff==1;
     }

Answer 1

Look at neighb.clear();, You are calling on the same object you put in your Hashtable. You are clearing your list soon after putting it in the Hashtable. May you want to create a new local arraylist, add all elements to the new arraylist add then add the new arraylist in Hashtable and then clear your neighb e.g.

      List<String> newList = new ArrayList<String>();
      newList.addAll(neighb);
      data.put(words.get(i), newList);
      newList.clear();