public class Project2 {

    // I changed this to strings because it's easier to work with strings vs characters
    private static String[][] letterRelationships = {{},  //0
                                                   {},  //1
                                                   {"a", "b", "c"},  //2 THIS IS THE ROW
                                                   {"d", "e", "f"},  //3
                                                   {"g", "h", "i"},  //4
                                                   {"j", "k", "l"},  //5
                                                   {"m", "n", "o"},  //6
                                                   {"p", "q", "r", "s"}, //7
                                                   {"t", "u", "v"},  //8
                                                   {"w", "x", "y", "z"}}; //9

    public static void test() {

    }

public static ArrayList<String[]> getResults(String phoneNum){
    ArrayList<String[]> possibleLetters = new ArrayList<>();
    for (int i = 0; i < phoneNum.length(); i++){

        // Get the first number
        char c = phoneNum.charAt(i);

        // Convert character into String
        String s = Character.toString(c);

        // Convert String into int
        int position = Integer.parseInt(s); // This corresponds to the ROW in your 2D array above

        // Create an array to hold the row
        String[] row = new String[letterRelationships[position].length];

        // Fill the row
        for (int j = 0; j < row.length; j++) {
            row[j] = letterRelationships[position][j];
        }



        // Add this array to the ArrayList
        possibleLetters.add(row);


        /*
        if (phoneNum.charAt(i) == '2'){
            sequence.append(letterRelationships[2]);
        }
        if (phoneNum.charAt(i) == '3'){
            sequence.append(letterRelationships[3]);
        }
        if (phoneNum.charAt(i) == '4'){
            sequence.append(letterRelationships[4]);
        }
        if (phoneNum.charAt(i) == '5'){
            sequence.append(letterRelationships[5]);
        }
        if (phoneNum.charAt(i) == '6'){
            sequence.append(letterRelationships[6]);
        }
        if (phoneNum.charAt(i) == '7'){
            sequence.append(letterRelationships[7]);
        }
        if (phoneNum.charAt(i) == '8'){
            sequence.append(letterRelationships[8]);
        }
        if (phoneNum.charAt(i) == '9'){
            sequence.append(letterRelationships[9]);
        }
        */
    }


    return possibleLetters;
}

// Replace hashset with your vector.
public static HashSet<String> getPossibleWords(ArrayList<String> words, ArrayList<String[]> possibleLetters){
    HashSet<String> results = new HashSet<>();

    // Get the first word in the list
    for (int i = 0; i < words.size(); i++) {
        String aWord = words.get(i);

        // Keep track if the word is legal
        boolean isLegal = true;

        // Traverse the word
        for (int j = 0; j < aWord.length(); j++) {
            // Get the first letter of the word
            String s = Character.toString(aWord.charAt(j)).toLowerCase();

            // Check if the array contains this letter. If it doesn't, word is not legal
            if (!testLetters(s, possibleLetters.get(j))) {
                isLegal = false;
            }
        }

        // Add to array if legal
        if (isLegal) {
            results.add(aWord);
        }
    }


    return results;
}

public static boolean testLetters(String letterToTest, String[] row) {

    for (int h = 0; h < row.length; h++) {
        if (letterToTest.toLowerCase().equals(row[h].toLowerCase())) {
            // Is the letter part of the row? Yes, return true
            return true;
        }

    }

    // Reached here, not part of the letter
    return false;
}

public static void main(String[] args) {

    // Sample word list
    ArrayList<String> sampleWordStrings = new ArrayList<>();
    sampleWordStrings.add("Perfect");
    sampleWordStrings.add("Tuesday");
    sampleWordStrings.add("Country");
    sampleWordStrings.add("Pumpkin");
    sampleWordStrings.add("Special");
    sampleWordStrings.add("America");
    sampleWordStrings.add("Freedom");
    sampleWordStrings.add("Picture");
    sampleWordStrings.add("Husband");
    sampleWordStrings.add("Monster");
    sampleWordStrings.add("Seventy");
    sampleWordStrings.add("Nothing");

    // Sample Test

    // Sample number
    ArrayList<String[]> myPossibleLetters = getResults("2637422");
    // This should give us the following possibilities
    /*
     * SLOT         LETTERS
     * 0            A B C
     * 1            M N O
     * 2            D E F
     * 3            P Q R S
     * 4            G H I
     * 5            A B C
     * 6            A B C
     */

    // Test against the word list
    HashSet<String> myPossibleWords = getPossibleWords(sampleWordStrings, myPossibleLetters);

    // Print the results
    for (String word : myPossibleWords) {
        System.out.println(word);
    }

    // The only word in my small list that can be made is AMERICA so the output should be america

}

/*
public static MyVector compareResults(MyVector words, MyVector results){
    MyVector matches = new MyVector();                              //vector to store final (matching) results
    for (int i = 0; i < words.size(); i++){                         //so long as there are words in the list
        String currentWord = (String) words.elementAt(i);           //convert the word we're on to a String to iterate over
        for (int j = 0; j < currentWord.length(); j++)              //iterate over the char of the current word
            for (int k = 2; k < results.size(); k++){               //iterate over the results array elements
            char[] charOfDigit = (char[]) results.elementAt(k);     //convert the current sub-array to a single element
                for (int l = 0; l < charOfDigit.length ; l++){      //and iterate over the sub-array elements
                    if (currentWord.charAt(j) == charOfDigit[l])    //compare the word char to the digit's char
                        matches.append(currentWord);                //add matches to the list
                }
            }
        }
    return matches;
    }
    */
}