Java Modules

Modularization introduced in Java 9 is to help developers call out explicitly what are they going to use in their application and what features are they ready to expose.

You can see that JDK itself now is viewed as a combination of modules rather than a single monolith unit. One can mention all modules they are going to use in the application and keep the application lightweight. This can be done by adding a “requires” section in the module-info file.

Another problem Modules solve is when you are sharing your library (a jar), it exposes all the packages, though you might not want users to play around with internal helper files. The “exports” keyword gives you control over what is being exposed from the package.


module java.mymodule {
  requires java.sql;
  exports java.util.string;

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