Over the year, here are the top websites that i visit very frequently..
stackoverflow.com - for the code that doesn't work.
github.com - source code repository, list of open projects to help my code.
spring.io - to get references to java(Spring framwork), docs and guides.
dzone.com - so many blogs, many things to read and increase your knowledge.
journaldev.com - specially for java, there is so many tutorials that can help you understand core concepts of java and different frameworks.
sitepoint.com - great resource about ideas, tip and article.
scotch.io - (has well written article) for me it is great place to find dummy projects. which i can change further.
hackerrank.com - coding practice and challenges.
techgig.com - technical challenges, quiz, practice and you may also earn money if you win any challange.
hashnode.com - to share knowledge with each other around the world.
There is many more websites but the first came into my mind is here.