Because I’m in my very early 20s I missed out on the huge Java craze. Everything was Python when I started getting a more formal education and before then all my work was in C++. Knowing more languages would obviously look better on a CV but I mean if I would benefit in a practical sense? I have two friends who are long time Java devs. And recently another friend who generally works with legacy C++ based systems from the early 2000s late 90s period had to work on a bunch of stuff in Java. Java is clearly still in large scale use among older systems. So would it be likely that eventually I would need to work on Java systems myself when my job is mostly JavaScript currently?
I’m a full-stack web developer. I mainly focus on frontend TypeScript/Angular at the moment, but we still support older products made with JavaScript/AngularJS. Across different projects I have had backends using php, Python/Django, Java/JSP, C#/asp.net, JavaScript/Express. Some languages have features or frameworks that make them easier for certain use cases, but sometimes I don’t have any choice and one type of server is required to interface with external code or applications.
I don’t know how likely it is that you will encounter a situation where Java is required, but that situation did arise for me and I am still forced to use it to support one of our products. If I had a choice though I would always pick C# over Java, since C# is pretty similar, but in my opinion every change is an improvement, and I feel like it has a lot of extra features.
Your preferences might be different though so I agree with the other sentiment that you should give everything a try, and see which languages/frameworks appeal to you and you want to learn more about.