Coding Guidelines Reference:

http://www.iwombat.com/standards/JavaStyleGuide.html

http://www.javaexperience.com best for all topics

http://newjavafaqs.blogspot.in/p/core-java.html -- just FAQs, good one

http://howtodoinjava.com - one of the best for everything from core java to frameworks.

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http://javaconceptoftheday.com/

http://what-when-how.com/Tutorial/Java-SE-6/Java-SE-6-index.html

http://geekexplains.blogspot.in/2008/05/archives-from-category-java-10.html

http://javabynataraj.blogspot.in/ - ameerpet materials

http://instanceofjava.com

http://java2s.com/Book/Java/CatalogJava.htm

http://java2s.com/Book/Oracle/CatalogOracle.htm

http://programmingbydoing.com/

http://home.cogeco.ca/~ve3ll/jatutor0.htm#

http://web.stanford.edu/class/cs108/handouts141/ stanford java slides

http://www.javawithus.com/programs/

http://www.java-examples.com/

http://www.fluffycat.com/Java/Basics/

http://www.java2novice.com/

http://leepoint.net/

http://www.digizol.com/2008/07/java-sorting-comparator-vs-comparable.html

http://xahlee.info/java-a-day/java.html

http://www.jusfortechies.com/java/core-java/static-blocks.php

http://newtechnobuzzz.blogspot.in/ - also nice one

http://www.java-tips.org/java-se-tips-100019/24-java-lang.html

http://tutorials.jenkov.com/ - best for theoretical reading and understanding

http://www.mkyong.com/ - one of the best one, includes android as well

http://beginnersbook.com/

http://viralpatel.net/blogs/static-import-java-example-tutorial/

http://examplesofjava.com/exceptions/user-defined-exception-example.html

http://java2s.com/Tutorials/Java/String/Centers_a_String_for_a_large_size.htm

http://www.javatpoint.com/java-string

http://www.javaspecialists.eu/archive/archive.jsp

http://www.codejava.net/java-se/jdbc -- for good examples with projects

http://stackoverflow.com/questions/2784514/sort-arraylist-of-custom-objects-by-property - comparable, comparator examples

http://javahash.com/transform-xml-with-xstl-using-java/

http://mrjoelkemp.com/2011/11/java-hashset-with-custom-objects/