Collections

[Vallabhaneni Suresh Kumar]

What is a difference between Hashtable, HashMap and TreeMap? How do you decide which one to use?

Thank you

[Srinivasa Raghavan]

Hashtable, HashMap and TreeMap are map implementations these collection classes should be used when you need to store data in key/value pairs.

Unlike the other two classes TreeMap is a Sorted map , sorts the element in the natural order. Hash Map & Hashtable are Unsorted & Unordered , Difference between Hashmap & hashtable is Hash map allows one null key & many null values but hash table does not . Also Hash table is synchronized

[Stian Almaas]

Try reading the Collections trail at sun. That should answer your question.

[Tim McGuire]

I also recommend the Collections chapter in Bruce Eckel's Thinking in Java. Reading it and doing the provided exercises will help a lot.

[Mr. C Lamont Gilbert]

Hashtable is passe.