Unique Word Abbreviation

An abbreviation of a word follows the form <first letter><number><last letter>. 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.

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

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

class ValidWordAbbr(object):
    def __init__(self, dictionary):
        """
        initialize your data structure here.
        :type dictionary: List[str]
        """
        self.dict = collections.defaultdict(list)
        for word in dictionary:
            if len(word)>2:
                temp = word[0] + str(len(word) - 2 ) + word[-1]
            else:
                temp = word
            if word not in self.dict[temp]:
                self.dict[temp].append(word)

    def isUnique(self, word):
        """
        check if a word is unique.
        :type word: str
        :rtype: bool
        """
        if len(word) > 2:
            temp = word[0] + str(len(word) - 2) + word[-1]
        else:
            temp = word
        if self.dict[temp] == [] or (self.dict[temp]==[word]):
            return True
        else:
            return False

public class ValidWordAbbr {
    Map<String, String> dict;
    public ValidWordAbbr(String[] dictionary) {
        dict = new HashMap<>();
        String abbr;
        for (String word : dictionary) {
            abbr = getAbbr(word);
            if (!dict.containsKey(abbr)) //first time to encounter the new abbr
                dict.put(abbr, word);
            else if (!dict.get(abbr).equals(word)) // next time, original word is different
                dict.put(abbr, "-1"); // -1: not unique
        }
    }

    public boolean isUnique(String word) {
        String abbr = getAbbr(word);
        if (!dict.containsKey(abbr))
            return true;
        else
            return dict.get(abbr).equals(word) ? true : false;
    }

    private String getAbbr(String word) {
        int n = word.length();
        if (n < 3)
            return word;
        return "" + word.charAt(0) + (n - 2) + word.charAt(n - 1);
    }
}