[Advanced-java] improving performance of recursive algorithm

[chase@xxxxxxxxxxxxx (David Chase)]

> i'm wondering how i can increase the performance of a recursive
>algorithm..It takes data from a database and perform some tasks. It
>takes quite a while to complete the tasks when dealing with a large
>amount of data. The algorithm makes use of: 

> string concatenation
> type casting
> use of hashtable/Vector (necessary)
> use of labels

> does any of these affect the performance?

It could be the database, of course.  Be sure that you only
create one connection, instead of logging in multiple times
(that would be a big mistake, but you never know, so I mention it).

Hashtable and Vector are both synchronized datastructures.
Synchronization (especially on a multiprocessor) can be
very expensive (figure 10-80 CPU cycles, depending on
architecture, bus, clock rate, etc).

Unless you need synchronization at that fine grain, you
should (for performance) use HashMap and ArrayList.  If you
need larger-grained synchronization, use your own lock,
but wrapped around several of the simpler operations.

For string manipulation, be sure to do most of your work
in StringBuffers.  Once you are only examining them, they
can be Strings.

Now, of course, there's also the possibility that there's
problems with your algorithm, but that is another matter.

David Chase