Java hashmaps without the value?
Let's say I want to put words in a data structure and I want to have constant time lookups to see if the word is in this data structure.  All I want to do is to see if the word exists.  Would I use a HashMap (containsKey()) for this?  Hashmaps use key->value pairings, but in my case I don't have a value.  Of course I could use null for the value, but even null takes space.  It seems like there ought to be a better data structure for this application.

The collection could potentially be used by multiple threads, but since the objects contained by the collection would not change, I do not think I have a synchronization/concurrency requirement.

Can anyone help me out?

Thanks in advance.

jbu
Java hashmaps without the value?
===

Let's say I want to put words in a data structure and I want to have constant time lookups to see if the word is in this data structure.  All I want to do is to see if the word exists.  Would I use a HashMap (containsKey()) for this?  Hashmaps use key->value pairings, but in my case I don't have a value.  Of course I could use null for the value, but even null takes space.  It seems like there ought to be a better data structure for this application.

The collection could potentially be used by multiple threads, but since the objects contained by the collection would not change, I do not think I have a synchronization/concurrency requirement.

Can anyone help me out?

Thanks in advance.

jbu