Java equivalent of Perl's hash

Question

I\'ve been using a lot Perl hashes due to super flexibility and convenient. for instance, in Perl I can do the following:

$hash{AREA_CODE}->{PHONE}->{S         


        

Answer 1

You can easily subclass your hash to add a method that'll autovivify for you.

From: $hash{AREA_CODE}->{PHONE}->{STREET_ADDR}

To: hash.vivifyingGet(areaCode).put(phone, streetAddr).

Assuming I've created the hash with:

/**
  * A two-level autovivifying hashmap of X and Y to Z. Provides
  * a new method #vivifyingGet(X) which creates the next level of hash.
  */
Map> hash =
    new HashMap>() {
    /**
      * Convenience method to get or create the next level of hash.
      * @param key the first level key
      * @return the next level map
      */
    public Map vivifyingGet(Phone key) {
        if (containsKey(key)) {
            return get(key);
        } else {
            Map = hash = new HashMap();
            put(key, hash);
            return hash;
        }
    }
};