As I say every time someone asks (that would make it a FAQ) IMNSHO:

The Programmer's certification is basically worthless. It is a better
indicator of how well you can memorize and regurgitate the Java language
specification and covered portions of the platform API than it is an
indicator of how well you can actually program in Java -- ie, it tests
factual knowledge rather than how to go about producing quality software.
Having said that, it is a pre-requisite to every other Java certification.

The Developer's certification is worth something; the task is a small-medium
programming assignment with somewhat ill-defined requirements, and is
something akin to an assignment one might find in the real world. The
assignment itself should take 12-20 hours of design and coding; the
follow-up exam allows several hours, but is very generous time-wise.

Pointers: get a refresher reference for the Programmer's test, and memorize
it. When you're taking the exam, follow all instructions to the letter.
Multiple choice questions sometimes ask you to mark ALL the correct
statements; you must find and mark each one for the question to count at
all. Other times, they ask for the THE MOST CORRECT statement. Be sure you
know which variety you're answering for each question.

For the Developer's certification: do your best. Follow all the
instructions. Take the "exam" that is required for it soon after completing
and submitting the assignment. The "exam" wants free-form rationale for
design decisions you took in completing the assignment. It is a big help if
you take this exam soon after completing the assignment, so that you
remember all of the details.

Neither certification has ever helped me in any way in gaining a job. If I
were sorting resumes, a certification might pique my interest a little but
it wouldn't put any candidate over the top.

-- Adam Maass