Java package
Java package is a mechanism for organizing Java classes into namespaces similar to the modules in Modula.
There is package-access level - it is default if there is no other access specified.
Classes from the same package could access to default (package-access level) and protected members of classes in the same package.
Core packages in Java SE6:
java.lang
java.util
java.io
java.math
java.nio
java.net
java.security
java.sql
java.awt
java.swing
java.applet