With a solid background in C/C++, Java should be relatively straight forward to pick up. I think one of the best free resources for learning java is the java website, http://java.sun.com , which has the API documentation and lots of great tutorials.
In terms of books I would probably recommend starting with something that describes the differences and similarities between C++ and Java. I actually learned Java first and then went onto C++, and the book I used was C++ for Java Programmers by Mark Allen Weiss. I'm sure there would be a similar book out there for "Java for C++ Programmers".
Also, check out the sticky at the top of this forum for more great learning resources.
Have look on this post (sticky post on top of Java forum section), it does explain what you need for Java development, where to get it, but also mention few free ebooks plus hard copies to get from the library/shop
-Java, How To Program 7th edition (Deitel & Deitel)
-Head First Design Patterns
I suggest reading both in parallel. You will find both to be an easy read (in my opinion at least) until you get to harder concepts in the 16+ chapters of Deitel&Deitel book or occasionally in the Design Patterns book.
You'll, of course want to read Java, How To Program more often than Design Patterns (up to Inheritance/Polymorphism) then you may want to start reading Design Patterns.