| DTMStringPool is an "interning" mechanism for strings. It will
create a stable 1:1 mapping between a set of string values and a set of
integer index values, so the integers can be used to reliably and
uniquely identify (and when necessary retrieve) the strings.
Design Priorities:
- String-to-index lookup speed is critical.
- Index-to-String lookup speed is slightly less so.
- Threadsafety is not guaranteed at this level.
Enforce that in the application if needed.
- Storage efficiency is an issue but not a huge one.
It is expected that string pools won't exceed about 2000 entries.
Implementation detail: A standard Hashtable is relatively
inefficient when looking up primitive int values, especially when
we're already maintaining an int-to-string vector. So I'm
maintaining a simple hash chain within this class.
NOTE: There is nothing in the code that has a real dependency upon
String. It would work with any object type that implements reliable
.hashCode() and .equals() operations. The API enforces Strings because
it's safer that way, but this could trivially be turned into a general
ObjectPool if one was needed.
Status: Passed basic test in main().
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