Total number of messages in the queue can be found using
queue.browse() method. This method basically reads the queue without
deleting values from the queue as deletion happens with
queue.receive() message. browsing the queue might be helpful to
determine the queue length though this approach is feasible for
smaller (and fixed length) queues where there is not much overhead
timing vise.

I don't understand what do you mean by messages pending! as only
measurable thing in JMS Queue in number of messages contained. If you
mean that messages pending are those which are waiting to be written
into the fixed-length-queue, I don't 've exact answer to this as it
will depend upon how insertion functionality works.
Note: queue is an instance of Weblogic's JMS Queue implementation.

Also Weblogic's console provide JMS Monitoring page where you can see
number of messages present in the queue plus some other details.

With Regards

I notice that you did get a reply later, but a thought about how
to do better another time, maybe:  If your question is specific
to JMS / Weblogic (and I can't really tell since I don't know
anything about either of these), maybe it would help to put that in
the subject line -- "read messages from JMS server" or something.
That way people who don't read all the threads but have the right
background to answer your question would be more likely to notice it.