I started learning programming in school with C++. But, currently, I am taking Data Structures and Algorithm course, and it is only given in Java. I also have a mobile app development course which uses Java. Some jobs also requires Java. I want to be flexible. Are there any good forum for Java which members are very helpful and has a lot of active members like this site. If you know also good forums for other languages, let me know as well for future reference.
java and js are scattered. There are forums but nothing big, or pieces of multi-language ones. I would instead just say to search very precisely what you want to know and you will get an answer quickly. SO is fine, they just have low tolerance for repeated questions or simple LMGTFY questions so search before you ask there.
BTW, Java and Javascript are two very different languages, with a wholly different object model. (JS's, in particular, will throw you for a loop if you don't read up on it first.