Keyboard Row

Given a List of words, return the words that can be typed using letters of alphabet on only one row's of American keyboard like the image below.

Example 1:

Input: ["Hello", "Alaska", "Dad", "Peace"]
Output: ["Alaska", "Dad"]

Note:

1. You may use one character in the keyboard more than once.
2. You may assume the input string will only contain letters of alphabet.

public class Solution {
    public String[] findWords(String[] words) {
        List<String> result = new ArrayList<String>();
        Character[] row1 = {'Q', 'W', 'E', 'R', 'T', 'Y', 'U', 'I', 'O', 'P'};
        Character[] row2 = {'A', 'S', 'D', 'F', 'G', 'H', 'J', 'K', 'L'};
        Character[] row3 = {'Z', 'X', 'C', 'V', 'B', 'N', 'M'};
        List<Character> list1 = Arrays.asList(row1);
        List<Character> list2 = Arrays.asList(row2);
        List<Character> list3 = Arrays.asList(row3);
        
        for (String word : words) {
            String newWord = word.toUpperCase();
            
            int i = 0, key = -1, n = newWord.length(); 
            int counter1 = 0, counter2 = 0, counter3 = 0;
            while (i < n) {
                if (list1.contains(newWord.charAt(i))) counter1++;
                else if (list2.contains(newWord.charAt(i))) counter2++;
                else if (list3.contains(newWord.charAt(i))) counter3++;
                
                i++;
            }
            
            if (counter1 == n || counter2 == n || counter3 == n)
                result.add(word);
        }
        return result.toArray(new String[result.size()]);
    }
}