JAVA A_Z

http://congdongjava.com/forum/threads/42-b%C3%A0i-t%E1%BA%ADp-java-c%C6%A1-b%E1%BA%A3n-c%C3%B3-%C4%91%C3%A1p-%C3%A1n-tham-kh%E1%BA%A3o.2555/
http://uet.vnu.edu.vn/tltk/Learning/File_PDF/BTjava_full.pdf
http://developersoftwares.blogspot.com/search/label/lap%20trinh%20java
http://ksec.info/forums/java.2/
http://hoidapit.com.vn/Questions/Questions/22345/cau-hoi-moi-nhat.html?q=java
http://toithacmac.wordpress.com/2013/12/12/phan-i-interface-va-abstract-trong-java/
http://tranhoangminh.wordpress.com/2012/10/18/su-khac-biet-giua-ham-equals-va-operator/
http://www.ddth.com/showthread.php/77568-L%C3%A0m-%C6%A1n-gi%E1%BA%A3i-th%C3%ADch-abstract-class-abstract-method-and-interface
http://www.khamphacntt.com.vn/linh-vuc/java.html
http://kythuatlaptrinh.com/noi-dung/phan-biet-interface-va-lop-abstract-trong-oop.html
http://nguyenhuuhai53.blogspot.com/
http://kythuatlaptrinh.com/noi-dung/phan-biet-interface-va-lop-abstract-trong-oop.html
lí thuyết 

http://www.javatpoint.com/java-oops-concepts
http://www.ibm.com/developerworks/vn/edu/j-introjava/section7.html
http://www.khamphacntt.com.vn/linh-vuc/java.html
http://www.daonho.com/search/label/Java
lí thuyết C# gần giống java
http://www.codeproject.com/Articles/838365/Basic-Csharp-OOP-Concept