Oracle Technology Network - Java

The Java section of Oracle Technology Network is the official site for Java developers. It includes links to Products, Downloads, Documentation, APIs and other useful information.

java.net

java.net - The Source for Java Technology Collaboration - A site for developers interested in participating in various Java technology projects.

JavaRanch

JavaRanch hosts discussion forums and FAQs for a wide range of Java related topics. JavaRanch has a separate discussion forum for every professional certification in Java technologies. These forums can be helpful for developers preparing for the corresponding certification exams.

IBM developerWorks - Java technology

IBM developerWorks - Java technology is a great resource for information on Java technologies and Java-based products. It includes online tutorials, technical articles, and IBM Redbooks.

www.java2s.com

Programming tutorials and source code examples includes a large number of online tutorials and source code examples organized by topic. The Java source code examples are located under the Java link.