Java probably still has a long future ahead, especially because Android app dev is done in Java. There are also lots of jobs around.
On the other hand, a lot of Java jobs involve stuff like enterprise Java, which can be horrible to work with.
C is probably good to know, so I'd play around with it for a few weeks and then move on to Rust. Knowing C probably lets you appreciate Rust even more.
Java is also good to know and not hard to get into. But for hobby projects I'd choose something else, unless you want to do Android apps.
Edit: Python is also a great all-round high level language and there are many Python jobs around :)
On the other hand, a lot of Java jobs involve stuff like enterprise Java, which can be horrible to work with.
C is probably good to know, so I'd play around with it for a few weeks and then move on to Rust. Knowing C probably lets you appreciate Rust even more.
Java is also good to know and not hard to get into. But for hobby projects I'd choose something else, unless you want to do Android apps.
Edit: Python is also a great all-round high level language and there are many Python jobs around :)