This sounds great for applications. But for libraries, you'll likely end up with the diamond dependency problem: an application uses two libraries, and each library uses their own copy of a third library.
So basically with Java you would need to flatten all dependencies and resolve version conflicts in some way (sometimes you must downgrade one library or even declare that some libraries are not compatible with each other, but that's a rare occasion).
AFAIK npm uses hierarchical dependencies, so few libraries with a different versions are not a problem at all (at least if those libraries are good citizens and don't pollute global namespace or use it carefully).
> Dependency mediation - this determines what version of an artifact will be chosen when multiple versions are encountered as dependencies. Maven picks the "nearest definition". That is, it uses the version of the closest dependency to your project in the tree of dependencies. You can always guarantee a version by declaring it explicitly in your project's POM. Note that if two dependency versions are at the same depth in the dependency tree, the first declaration wins.