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What's the difference between Dictionary and Hashtable and how do I work with the Dictionary class in Java?
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A Dictionary<TKey,TValue> of a specific type (other than Object) provides better performance than a Hashtable for value types. This is because the elements of Hashtable are of type Object; therefore, boxing and unboxing typically occur when you store or retrieve a value type.
In Python, dictionaries (or “dicts”, for short) are a central data structure: Dicts store an arbitrary number of objects, each identified by a unique dictionary key. Dictionaries are often also called maps, hashmaps, lookup tables, or associative arrays.
In Java the HashMap implements the Map interface while the Dictionary does not. That makes the Dictionary obsolete (according to the API docs). That is, they both do a similar function so you are right that they seem very similar...a HashMap is a type of dictionary.
Dictionary is a generic type and returns an error if you try to find a key which is not there. The Dictionary collection is faster than Hashtable because there is no boxing and unboxing.
Dictionary is an abstract base class of Hashtable. Both are still in JDK for backwards compatibility with old code. We are expected to use HashMap and other implementations of Map interface introduced in Java 1.2.
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