------------BOOKS---------------

https://github.com/EbookFoundation/free-programming-books/blob/master/free-programming-books.md

------------EXERCISES---------------

https://www.e-olymp.com/en/

https://leetcode.com/

http://exercism.io/

------------JAVASCRIPT---------------

http://voidcanvas.com/

------------JAVA---------------

http://skipy.ru/technics/synchronization.html#monitors

http://www.angelikalanger.com/GenericsFAQ/FAQSections/ProgrammingIdioms.html#FAQ104

https://www.geeksforgeeks.org/java/

http://www.javenue.info/post/84

https://www.tutorialspoint.com/java/lang/system_arraycopy.htm

-----OTHER---