In terms of Java, both the class
HashMap and the class
Dictionary are implementations of the “Map” abstract data type. Abstract data types are not specific to any one programming language, and the Map ADT can also be known as a Hash, or a Dictionary, or an Associative Array (others at http://en.wikipedia.org/wiki/Associative_array). (Notice we’re making a distinction between the
Dictionary class and the Dictionary ADT.)
Dictionary class has been marked as obsolete, so it’s best not to use it.