There are hundreds of websites available for students in internet. Some of them teaches the core concepts so clearly that, it make students very easy to learn and remember the concepts. Though youtube provides educational channels these sites also help students to a very large extend. So don't forget to check the links. Happy Learning :)
http://www.java2s.com/ http://www.c-sharpcorner.com/ http://www.sqlcourse.com/index.html
http://docs.oracle.com/ www.w3schools.com/ www.java-samples.com/