What is the best way to learn Java?

What is the best way to learn Java? I am a development-oriented person and am interested in learning Java “quickly and painlessly”. I have a couple of years experience developing in C and Access, and more recent experience in mainframe languages (JCL, COBOL, etc.).

Also, should I get certified? How long will it take? What is certification “worth” in the field, as opposed to no certification?