2.1. Introduction¶

In Java, a package allows you to organize classes that have related functionality. Proper code organization becomes increasingly important as the size of the project increases.

More formally, a package is a grouping of related types providing access protection and name space management. Note that types refers to classes, interfaces, enumerations, and annotation types [1].

When a class is contained within a package, its fully qualified name (or FQN for short) consists of two parts: the name of the package followed by the class name (sometimes referred to as the simple class name to differentiate it from the FQN). By convention, the simple class name will always begin with a capital letter.

For example, you have likely used the Scanner class in the past. You may also remember importing java.util.Scanner at the top of some of your programs. Here, the simple class name is Scanner and its package is java.util.

Note

When you import a class, you have to use its FQN, but once the class is imported, you can use its simple class name.

The two primary benefits of packages are:

Name Space Management:

Packages allow you to give a common name to a group of related types. For example, java.util.Scanner and java.util.Random are two utility classes provided in the java.util package. You and other programmers can easily determine that these types are related based on their package. They are both utilities that you have probably used in your code.

Note

You could have two types with the same simple name that are located in different packages. For example, you could have a java.util.Random class and a edu.cs.uga.Random class. Both classes have the same simple class name (Random) but they can be differentiated by their package names.
Access Protection:

Visibility in Java is not limited to public and private. Packages and additional visibility modifiers enable programmers to declare entities as visible only within a package. We will discuss this in more detail when we cover visibility.

In this chapter, you will create multiple classes, group them into a package, then compile and run them. The expectation is that you will follow along with this tutorial in a terminal emulator on Odin or some Unix machine. You should ask questions on Piazza if you are unable to proceed or if some aspect of the tutorial is particularly confusing.