Imports and Libraries

Created By: Geoffrey Challen
/ Updated: 2022-05-23

This may be the most important lesson of the entire semester! All kinds of other people are creating and freely sharing useful Java code! And now you'll learn how to build on top of those contributions. Don't try to do it yourself! You are not alone...

Objects Beyond String

So far our understanding of Java objects has focused on Strings. We've seen how to create them using new:

And how to access useful String methods, like length, substring, and split. And we've used these methods to solve problems:

Strings are built in to Java, meaning that we don't need to use import statements to access them. But Java allows you to access lots of other kinds of objects that might be useful for solving other kinds of problems! This lesson looks at how to access these other objects in your own code and provides some examples of useful objects and libraries.

import and Libraries

Computer science is a remarkably collaborative field. In no other pursuit are millions of people all across the world so freely willing to share their creations!

Because of this, changing the world through your code has never been easier. Let's see how!

First, let's see how we find interesting and useful Java code that is part of the Java standard library.

Provide an overview of the Java Standard Library.

Next, let's see how to actually load those library classes into our project.

Show how to use the import keyword.

Show how to complete the homework problem above. Feel free to cover multiple approaches!

Example Libraries

Now let's look at a few useful parts of the Java Standard Library. No claim that these are the most useful parts! They're just a few examples of code that is already out there for you to use!


Looking to make your Java programs more interesting? Try introducing some randomess! Let's see how.

Provide a Javadoc overview of java.util.Random.

Provide a code overview of java.util.Random.


Arrays are useful, but they seem to be missing a few features. Let's explore where they are hiding out!

Provide a Javadoc overview of java.util.Arrays.

Provide a code overview of java.util.Arrays.


Computers can do math, right? That might be useful! Let's get past +, -, *, and /.

Provide a Javadoc overview of java.math.

Provide a code overview of java.math.


One of the most important part of the Java Standard Library is the collections framework. It provides a variety of different ways of store things.

We certainly couldn't do it justice here. But we'll be covering several of these incredibly useful classes over the next few lessons!

Show how to complete the homework problem above. Feel free to cover multiple approaches!

More Practice

Need more practice? Head over to the practice page.