Hi there!! I am actually new to JAVA Lang. From here till now, I have learned how to code in C++ quite well. Thanks to coders like @Ashishgup, @mango_lassi for their clean coding style. If someone can point out other clean coders like them but who do it in JAVA, that would be of great help.
SecondThread also codes in java, you can have a look at his code. https://codeforces.net/profile/SecondThread
But I wouldn't really call his code clean. From my memory, some of the cleanest Java programmers on this site are Petr and Egor (although they have switched to C++, you can still read their older codes).