package « Java Source And Data Type « SCJP

1.3.1.The package name is a series of elements separated by periods.
1.3.2.Packages are identified by the package statement.
1.3.3.Use only alphanumeric characters in package names. package is imported by default and does not need to be imported by an import statement.
1.3.5.Other than java.lang, every other package you use must be named in an import statement