There are a lot of options when It comes to Java artifact repositories.
The most common public repo is maven central, but you can host also your own repo using archiva, Nexus, artifactory...
A repo must follow a well defined layout (how the files are organized), for example "maven layout", which is again the most common.
You can download libraries from the repos by directly downloading them or using build systems like maven itself or gradle.
So as you can see, in Java there are a lot of options. In contrast to npm, it's a bit more complicated to get started since Java relies on complex automation systems to provide dependency management.