Unique Word Abbreviation(Easy)

An abbreviation of a word follows the form . Below are some examples of word abbreviations:

a) it                      --> it    (no abbreviation)

     1
b) d|o|g                   --> d1g

              1    1  1
     1---5----0----5--8
c) i|nternationalizatio|n  --> i18n

              1
     1---5----0
d) l|ocalizatio|n          --> l10n

Assume you have a dictionary and given a word, find whether its abbreviation is unique in the dictionary. A word's abbreviation is unique if no other word from the dictionary has the same abbreviation.

Given dictionary = [ "deer", "door", "cake", "card" ]

isUnique("dear") -> false
isUnique("cart") -> true
isUnique("cane") -> false
isUnique("make") -> true

public class ValidWordAbbr {
    private Set<String> uniqueDict;
    private Map<String, String> abbrDict;

    public ValidWordAbbr(String[] dictionary) {
        uniqueDict = new HashSet<>();
        abbrDict = new HashMap<>();

        for (String word : dictionary) {
            if (!uniqueDict.contains(word)) {
                String abbr = getAbbr(word);
                if (!abbrDict.containsKey(abbr)) {
                    abbrDict.put(abbr, word);
                } else {
                    abbrDict.put(abbr, "");
                }

                uniqueDict.add(word);
            }
        }
    }

    public boolean isUnique(String word) {
        if (word == null || word.length() == 0) {
            return true;
        }

        String abbr = getAbbr(word);
        if (!abbrDict.containsKey(abbr) || abbrDict.get(abbr).equals(word)) {
            return true;
        } else {
            return false;
        }
    }

    private String getAbbr(String word) {
        if (word == null || word.length() < 3) {
            return word;
        }

        StringBuffer sb = new StringBuffer();
        sb.append(word.charAt(0));
        sb.append(word.length() - 2);
        sb.append(word.charAt(word.length() - 1));

        return sb.toString();

    }
}