a good recommendation!

By reading it.

Yes.

Yes.  The JavaDoc is supposed to be a comprehensive reference, which is
completely different from a tutorial guide.

Yes.  It's the only source of most of the information you'll need.

In general, if you are starting out to learn a new part of the Java library
(like Swing, or the security stuff, or networking, or...) it's better to find a
tutorial if you can.  Start with that, but don't stop there -- the tutorial
(even if its a whole book) is /not/ intended to give you all the information
you need to be able to program Java in that area.  A tutorial is intended to
give you an introduction to the area, and an overview of it, so that you can
find your own way around afterwards.

In some cases you won't need a tutorial, and in other cases you won't be able
to find one.  In either case you'll have to start with the JavaDoc.  A general
approach is to start by reading the package comments, and the brief
descriptions of each class.  That should give you at least /some/ idea of what
the package is all about and how it is structured.  (And if it doesn't then
remember how confusing it is when that happens, so that you can avoid giving
other people the same problem when they try to use /your/ software.)

Don't try to memorise everything in one go.  Don't even try to understand
everything in one go.  The idea is to try to get an overview of what's in the
package and roughly what it does, so that when you need the details of any
operation, you know roughly where find them.  Learning is a skill which
improves with practice -- in time you will get better and better at skimming
off
the important information from the JavaDoc without wasting too much time or
effort.

Expect to be reading the JavaDoc every single day of your life as a working
Java programmer.

   -- chris