We've looked at two language constructs you can use in the module descriptor--requiring modules and exporting packages. Together, they give you sufficient control over the interface of your modules and they address the two main goals of modularity--reliable configuration and strong encapsulation. However, in many real-world situations, you might sometimes find that these two alone are not enough to achieve certain things you want to do. For example, you may want to export a package from a module, only for it to be consumed by a certain other module, and not for public consumption. To handle many such special cases, the module system has some powerful features that we'll take a look at in this part of the chapter.
We looked at the problem of dependency leakage in Chapter 5, Using Platform APIs. The module that you depend on might have APIs that might also require you to use another module. Here's an example:
module A {
requires B;
}
...