How to Easily Use Custom Java Library Across Multiple Projects in IntelliJ IDEA

Learn how to turn your custom Java library into a reusable dependency for multiple projects using IntelliJ IDEA.
---
This video is based on the question https://stackoverflow.com/q/70439895/ asked by the user 'NightStorm' ( https://stackoverflow.com/u/8678114/ ) and on the answer https://stackoverflow.com/a/70439974/ provided by the user 'evren' ( https://stackoverflow.com/u/16635445/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How to use classes from one project in another project

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Easily Use Custom Java Library Across Multiple Projects in IntelliJ IDEA

When developing software, efficiency is key; you don't want to reinvent the wheel every time you start a new project. If you're working with Java and have a collection of reusable utilities—like file handling, string processing, and other common tasks—you might find yourself copying and pasting code from one project to another repeatedly. This not only increases the likelihood of errors but also makes your codebase harder to maintain.

In this guide, we will explore a more efficient way to use classes from one project in another: by turning your custom Java library into a dependency. You'll learn how to set up your IntelliJ IDEA to manage dependencies easily, ensuring code reuse without the hassle.

The Problem: Code Duplication

When building applications, it's common to create utility functions or classes that can be reused in multiple projects. Instead of copying these classes into every project where they are needed, you can streamline the process by turning them into a dependency. This not only saves time but also helps keep your projects organized.

The Solution: Adding Your Custom Library as a Dependency

Step 1: Build Your Custom Library as a JAR

First, you need to compile your custom library into a JAR (Java ARchive) file. A JAR file is a package file format that aggregates many Java class files and associated metadata into a single file. Here's how to do it:

Open your custom library project in IntelliJ IDEA.

Navigate to File Project Structure.

Under the Artifacts tab, click on the + icon to create a new artifact.

Choose JAR and then From modules with dependencies.

Select your main module and specify the output directory for the JAR.

Click OK to generate the JAR file.

Step 2: Add the JAR as a Dependency in Your New Project

Now that you have your JAR file, you need to include it as a dependency in your other Java projects:

Open the project where you want to use your custom library in IntelliJ IDEA.

Navigate to File Project Structure again.

Under the Libraries section, click the + icon and select Java.

Choose the JAR file you created and add it to your project.

Step 3: Configure Classpath

To ensure that your project recognizes the classes from the library, double-check that the JAR file is included in the module dependencies:

In the Project Structure window, go to the Modules section.

Select your module, then navigate to the Dependencies tab.

Make sure your newly added JAR is visible in the dependencies list.

Step 4: Use the Classes from Your Library

With everything set up:

You can now use any class from your custom library in your new project just like you would with any other library.

Simply import the required classes at the beginning of your Java files.

[[See Video to Reveal this Text or Code Snippet]]

This method allows you to maintain a single source of truth for your utility methods. If you ever need to update the logic in your library, you can do so in one place, and all projects will benefit from the change.

Conclusion

Making your custom Java library a reusable dependency across multiple projects not only saves time but also enhances the maintainability of your code. By following the steps outlined above, you can streamline your development process and minimize code duplication. Remember, effective use of libraries and dependencies is a best practice in software development that can greatly improve your productivity.

Now, stop copying and pasting and start building smart with your Java projects!

Видео How to Easily Use Custom Java Library Across Multiple Projects in IntelliJ IDEA канала vlogize