Project Jigsaw vs Maven

Very simplified answer

After Jigsaw, public will be public only within the JAR scope. To see the class outside the JAR it must be exported.

Java will force modularization because any inter module interaction will have to be specified in the module-info file.

For example, if you produce a WAR it will remain almost unchanged but all JARs packages in the WAR must define a module-info (or not define it and be treated as automatic or unnamed modules).

Maven has 2 main features: dependency management and building:

• Dependency management means Maven can determine versions of libraries and download them from repositiories.
• Building means Maven can compile code and package it into artifacts.

To conclude: Maven will still be responsible for building, but one must learn how to compile and package using Jigsaw modules.

Modules are not in any way a threat to build tools. Modules complement build tools because build tools construct a dependency graph of artifacts and their versions at build time while modules enforce dependencies of artifacts/modules (not including versions) at build time and run time.

From the State of the Module System:

"A module’s declaration does not include a version string, nor
constraints upon the version strings of the modules upon which it
depends. This is intentional: It is not a goal of the module system
to solve the version-selection problem, which is best left to build
tools and container applications."