Sort all words in a file by length in one reading. (Java)

Question

The purpose for my class of data structures is to find the shortest path from one word to another.

i.e. Start: bleed → blend → blond → End: blood, with a cost of 3.

I am given a list of words that I need to group using a map. Where:

Key: word length, Meaning: a set of all words with this length.

I have already finished the program, but I think I can improve the performance if I change the way the sets are stored on the map. Right now I am browsing a text file and saving every single word in an ArrayList, then browsing through an ArrayList and saving all the words of length x in the set, removing every word from the list. I continue from the first element in the ArrayList until the List is empty.

I was wondering if I can do this sorting while I am reading in a file, and generally avoid ArrayList.

This is the code I have:

ArrayList<String> wordList = new ArrayList<String>();
Map<Integer, Set> setMap = new HashMap<Integer, Set>();
Graph pathGraph = new Graph();

private void readFile(String file) {
    try {
        FileReader f = new FileReader(file);
        BufferedReader reader = new BufferedReader(f);
        String line = "";
        while ((line = reader.readLine()) != null) {
            wordList.add(line);
        }

    } catch (Exception e) { //Done in case of an exception
        System.out.println("No file found.");
    }
}

private void mapMaker() {
    int wordLength = 1;
    Set<String> wordSet = new HashSet<String>();
    while (!wordList.isEmpty()) {
        wordSet = setBuilder(wordLength);
        if (!wordSet.isEmpty()) {
            setMap.put(wordLength, wordSet);
        }
        wordLength++;
    }
}

private Set<String> setBuilder(int x) {
    Set<String> wordSet = new HashSet<String>();
    int counter = 0;
    while (counter < wordList.size()) {
        if (wordList.get(counter).length() == x) {
            wordSet.add(wordList.get(counter));
            wordList.remove(counter);
        } else {
            counter++;
        }
    }
    return wordSet;
}

Thank you for any input.

Answer 1

private void readFile(String file) {
    try {
        FileReader f = new FileReader(file);
        BufferedReader reader = new BufferedReader(f);
        String word = "";
        while ((word = reader.readLine()) != null) { 
            int length = word.length();
            if(setMap.containsKey(length)) {
                setMap.get(length).add(word);
            } else {
                Set set = new HashSet<String>();
                set.add(word); 
                setMap.put(length, set);
            }
        }

    } catch (Exception e) { //Done in case of an exception
        System.out.println("No file found.");
    }
}

Answer 2

You can use Guava MultiMap :

Example:

        String[] words={"world","hello","abc","bcd","abc"};
        SetMultimap<Integer,String> lenMap=HashMultimap.create();
        for(String str:words)//instead read word from file in your case
            lenMap.put(str.length(),str);

Conclusion:

{3=[abc, bcd], 5=[hello, world]}