Provides access to the content of a module.

A module reader is intended for cases where access to the resources in a module is required, regardless of whether the module has been loaded. A framework that scans a collection of packaged modules on the file system, for example, may use a module reader to access a specific resource in each module. A module reader is also intended to be used by ClassLoader implementations that load classes and resources from modules.

A resource in a module is identified by an abstract name that is a '/'-separated path string. For example, module java.base may have a resource "java/lang/Object.class" that, by convention, is the class file for java.lang.Object. A module reader may treat directories in the module content as resources (whether it does or not is module reader specific). Where the module content contains a directory that can be located as a resource then its name ends with a slash ('/'). The directory can also be located with a name that drops the trailing slash.

A ModuleReader is open upon creation and is closed by invoking the close method. Failure to close a module reader may result in a resource leak. The try-with-resources statement provides a useful construct to ensure that module readers are closed.

A ModuleReader implementation may require permissions to access resources in the module. Consequently the find, open, read, and list methods may throw SecurityException if access is denied by the security manager.