Java Internals

Java Threading:
Thread, Concurrency, and Synchronization

Java Design Pattern: 
http://www.programcreek.com/category/design-patterns/
http://javarevisited.blogspot.in/2012/06/20-design-pattern-and-software-design.html
http://www.programcreek.com/java-design-patterns-in-stories/

Java Memory Model and Memory Leaks:

http://www.cubrid.org/blog/dev-platform/understanding-jvm-internals/

http://coding-geek.com/jvm-memory-model/

http://www.programcreek.com/2011/11/what-do-java-objects-look-like-in-memory/
http://www.programcreek.com/2013/04/what-does-a-java-array-look-like-in-memory/
http://www.programcreek.com/2011/10/how-java-compiler-generate-code-for-overloaded-and-overridden-methods/
http://www.programcreek.com/2013/10/the-introduction-of-memory-leak-what-why-and-how/
http://www.programcreek.com/2011/10/java-class-instance-initializers/

Java Garbage Collection:

https://www.interviewcake.com/concept/java/lazy

https://www.interviewcake.com/concept/java/slice?

https://www.interviewcake.com/concept/java/garbage-collection?

Java Advanced:

http://www.programcreek.com/advanced-topics/

Java Framework:

http://www.programcreek.com/2011/09/what-is-the-difference-between-a-java-library-and-a-framework/

http://www.programcreek.com/2011/09/how-to-design-a-java-framework/

http://www.programcreek.com/2011/07/build-a-java-library-for-yourself/

http://www.programcreek.com/2012/08/reflection-problem-on-java-framework/

Java Misc:

https://www.interviewcake.com/concept/java/mutable?

http://javarevisited.blogspot.in/2011/09/difference-hashmap-vs-hashset-java.html