You can create a hierarchy of packages using a qualified name. We mentioned this term in the previous section without going into its details.
A qualified name is a sequence of identifiers separated by dots. Here are some examples of qualified names.
java.lang
java.util
java.io
com.onecube
com.onecube.model
com.onecube.module.storage
zen.core
javafx.stage
Here is the general form of a hierarchical package statement.
package level1.level2.level3;
Each identifier in a qualified name, separated by a dot, creates a node or level in your hierarchy. A package hierarchy must be reflected in your file system. Which means, if you change the name of your package, you should change the directory structure, too.
For example, a package declared as package com.example should be stored in
the com/example directory.