Calling and Importing Classes Defined in Unnamed Packages

JDK Tutorials - Herong's Tutorial Examples

∟Calling and Importing Classes Defined in Unnamed Packages

This chapter provides tutorial notes and example codes on localization methods and resource bundles. Topics include using java.text.SimpleDateFormat and java.text.DecimalFormat locale sensitive methods; using java.util.ResourceBundle class to define localization resource bundles; using java.util.PropertyResourceBundle class to read properties files as resource bundles.

What Is an Unnamed Package?

One Class in an Unnamed Package - Hello.java

Two Classes in Unnamed Packages - Hello.java and CallingHello.java

Importing Classes Defined in Unnamed Packages

Importing Classes from Unnamed to Named Packages

Importing Classes from Unnamed to Named Packages - JDK 1.4.1

Conclusion:

The JDK compiler will compile the imported classes if not compiled yet and source codes are available in the class path.
There is really only one unnamed package. All classes defined without a package name are considered to be in this single unnamed package.
With JDK 1.3.1 and lower versions, import statement is allowed on classes defined in the unnamed package.
With JDK 1.4.1 and higher versions, import statement is not allowed on classes defined in the unnamed package.
If you have an old class defined in the unnamed package which cannot be directly imported to any classes in named packages with JDK 1.4.1, and you don't have the source code for that old class, you can create a wrapper class in a named package, and compile it with JDK 1.3.1. The wrapper class can then be imported to any classes with JDK 1.4.1.