Java Projects - Second Edition

Why modules are needed

We have already seen that there are four levels of access in Java. A method or field can be private, protected, public, or default (also known as package private) when no modifier is supplied inside a class. When you develop a complex library to be used in several projects, the library itself will contain many classes in many packages. There will certainly be classes and methods, fields in those that are supposed to be used solely inside the library by other classes from different packages. These classes are not to be used by the code outside the library. Making them anything less visible than public will render them unusable inside the library. Making them public will make them visible from outside. This is not good. ...