Online Oracle J2EE books

Oracle® Application Server Containers for J2EE Enterprise JavaBeans Developer's Guide

Other online books

and more books

Have to read

Check this forum http://forums.dzone.com/ and this http://www.javalobby.org/java/forums/t103829.html

http://docs.rinet.ru/JWP/ch16.htm

All about interview

This is helpful one for interviews.

Java Topics

1. Core API
2. String StringBuffer StringBuilder
3. Threading and concurrency
4. Serialization and Externalization
5. Util package
6. Garbage Collection
7. Java 5.0 and 6.0 features
     Generics
     Annotations
     Enhanced For Loop
     Autoboxing and unboxing
     Typesafe Enums
8. JVM and Code Optimization
9. Class Loader Architecture
10. Java Security Sandbox
11. JMX
12. Cloning , Comparator Vs Comparable
13. Memory Model
14. Problems faced with multi threaded programs
15. General Java Design Patterns

FAQ

http://technologiquepanorama.wordpress.com/

Cloning

http://macchiato.com/columns/Durable6.html

Behind scenes of enhanced for loop

The for-each loop can be used with identifiers whose type is Iterable or its an Array type.
From JLS

The Expression must either have type Iterable or else it must be of an array type (§10.1), or a compile-time error occurs.


Now that following in the java.lang.Iterable javadoc

All Known Subinterfaces:
BeanContext, BeanContextServices, BlockingQueue, Collection, List, Queue, Set, SortedSet

Java 5 and 6 enhancements

http://java.sun.com/j2se/1.5.0/docs/relnotes/features.html
http://java.sun.com/javase/6/webnotes/features.html

and a nice link to show diff between Java 5 and 6 beta
http://java.sun.com/javase/6/jcp/beta/apidiffs/index-diffs.html

Must reads on Threads and synchronization

Some of the excellent links that I have come across and which I wouldn't love to miss

Java Memory Model
Jermey Manson Blog
JMM from IBM Library
Volatile from IBM library
If I weee King: A proposal for fixing the Java programming language's threading problems
Writing multi threaded java apps
Multi threading