Best tutorials online

Following are some of best free tutorials that I come across online. These are super cool to follow.

Java tutorials:

Java Brains:

Official website: https://javabrains.io
Youtube channel: https://www.youtube.com/channel/UCYt1sfh5464XaDBH0oH_o7Q

jenkov tutorials:

Official website: http://tutorials.jenkov.com/

Design Patterns:

Youtube channel(Christopher Okhravi): https://www.youtube.com/channel/UCbF-4yQQAWw-UnuCd2Azfzg

System Design:

Tech Dummies channel on youtube: 

https://www.youtube.com/channel/UCn1XnDWhsLS5URXTi5wtFTA

Educative Course on System design:

https://www.educative.io/courses/grokking-the-system-design-interview

Gaurav Sen's channel on youtube:

https://www.youtube.com/channel/UCRPMAqdtSgd0Ipeef7iFsKw

Object Oriented Design:

Educative course:

https://www.educative.io/courses/grokking-the-object-oriented-design-interview