Using Packages - kleinay/arieloop2026 GitHub Wiki

A Few words on Java Packages

Java code is organized into packages. We will learn more about packages later in this class.

For now, however, note that java classes may have long names, for example, there are classes named java.awt.Color and java.util.Random.

You can use these long names (a.k.a the class' fully-qualified name):

public class Example {
   public static void main(String[] args) {
      java.util.Random rand = new java.util.Random();
   }
}

but it might be inconvenient because that's a lot to type.

We call the part before the last period the package name, and the part after the last period the last name.

The import keyword tells java that, in this file, you can use only the last name of some of the classes.

import java.util.Random;

tells java that in this file, you can use Random instead of java.util.Random.

import java.util.Random;

public class Example {
   public static void main(String[] args) {
      Random rand = new Random();
   }
}

import java.util.*;

Tells java that in this files, you can use the last name of every class with the package name java.util., including Random.

It is better to not use the * version, because it makes it hard to understand where the names come from.