There are countless places online to learn about this. Probably numerous MOOCs that teach OOP and probably Java. Here is one possibility, I have no idea how it compares to others, that's just from a quick google search.
A few things I'd also highly recommend you spend some time wrestling with, after you learn some of the basics of Java:
SOLID principles (wiki (article)
Software design patterns (wiki) (java examples)
(Keep in mind that the design patterns should not be overzealously used. A lot of people go nuts trying to wedge them into every solution, as if they'll reach Nirvana if only they combine the right design patterns the right way. 80-20 rule comes to mind here, as well as using the right tool for the job, and KISS principle. Do what is most effective given what the problem actually demands. This doesn't mean take shortcuts on writing clean code, though.)