Tips For Reading Code

As developers, we spend more time reading code than writing it, and this video provides tips to enhance your code-reading skills within the IntelliJ IDEA IDE. Learn how to leverage features like syntax highlighting, inlay hints, and code formatting to navigate and understand code effortlessly. Discover techniques to quickly scan code, collapse and expand sections for efficient navigation, and use powerful search functionalities to locate specific elements.

Whether you’re a beginner or an experienced developer, these tips will empower you to read and comprehend code with confidence, making your coding journey in IntelliJ IDEA a seamless and productive experience.

Links

IntelliJ IDEA Pro Tips: Selectively Commit Changes to a File

While working on a new feature, you find some small other things to fix. Since these changes are unrelated, you probably shouldn’t commit them together. You could revert these changes to redo them separately, but who wants to do extra work? Fortunately, you can now select which chunks or even lines of changes to add to your commit. You can commit the rest separately or even move it to a new change list.

Links

IntelliJ IDEA: Explore project structure with the Dependency Matrix

When working with large, complex software projects, we need to understand the dependencies between components in your projects.

#IntelliJIDEA‘s Dependency Structure Matrix (DSM), or Dependency Matrix, that can help us with this! Let’s take a look at how to use the Dependency Structure Matrix to see dependencies between different components, like modules, packages, and classes. See how to identify dependencies, find cyclic or mutual dependencies, and visualize the flow of dependencies to see which components use or depend on other components and vice versa.

Overview of IntelliJ IDEA 2023

IntelliJ IDEA is designed to help developers like us stay in the flow while we’re working. Like all IDEs, it has a lot of functionality available, but it’s designed to get out of your way to let you focus on the code.

Take a look at this overview of IntelliJ IDEA.

Introduction

  • Find Action: ⌘ ⇧ A (on macOS) / Ctrl+Shift+A (on Windows/Linux)
  • Feature Trainer
  • Hide all windows: ⌘ ⇧ F12 (on macOS) / Shift+Command+F12 (on Windows/Linux)
  • Project tool window: ⌘1 (on macOS) / Alt+1 (on Windows/Linux)
  • Quick Switch Scheme: ^`(on macOS) / Ctrl+` (on Windows/Linux)
  • IDE viewing modes
  • Preferences: ⌘, (on macOS) / Ctrl+Alt+S (on Windows/Linux)

Coding assistance

  • Code completion
  • Complete Current Statement: ⌘ ⇧ ⏎ (on macOS) / Shift+Ctrl+Enter (on Windows/Linux)
  • Show Context Actions: ⌥ ⏎ (on macOS) / Alt+Enter (on Windows/Linux)
  • Intention actions
  • Navigate to next highlighted error: F2
  • Navigate to previous highlighted error: Shift F2
  • Generate code: ⌘ N (on macOS) / Alt + Insert (on Windows/Linux)
  • Live templates

Refactoring

  • Rename: Shift F6
  • Extend selection: ⌥ Up (on macOS) / Ctrl+W (on Windows/Linux)
  • Extract variable: ⌘ ⌥ V on macOS) / Ctrl+Alt+V (on Windows/Linux)
  • Postfix completion
  • Reformat code: ⌘ ⌥ L (on macOS) / Ctrl+Alt+L (on Windows/Linux)
  • Move statement up: ⇧⌘ Up (on macOS) / Ctrl+Shift+Up (on Windows/Linux)
  • Surround with: ⌘ ⌥ T (on macOS) / Ctrl+Alt+T (on Windows/Linux)
  • SmartType Completion: ^ ⇧ Space  (on macOS) / Shift+Ctrl+Space (on Windows/Linux)
  • Inline: ⌘ ⌥ N (on macOS) / Ctrl+Alt+N (on Windows/Linux)
  • Extract method: ⌘ ⌥ M on macOS) / Ctrl+Alt+M (on Windows/Linux)

Testing & Debugging

Navigation

  • Navigate backwards: ⌘ [ (on macOS) / Ctrl+Alt+Left (on Windows/Linux)
  • Navigate forwards: ⌘ ] (on macOS) / Ctrl+Alt+Right (on Windows/Linux)
  • Find usages / declaration: ⌘ B (on macOS) / Ctrl+B (on Windows/Linux)
  • Recent Files: ⌘E (on macOS) / Ctrl+E (on Windows/Linux)
  • Recent locations: ⇧⌘E (on macOS) / Ctrl+Shift+E (on Windows/Linux)
  • Search everywhere: ⇧⇧ (on macOS) / Shift Shift (on Windows/Linux)
  • Find in files: ⇧⌘F (on macOS) / Ctrl+Shift+F (on Windows/Linux)

Reading Code

  • Folding -> Expand: ⌘ + (on macOS) / Ctrl+ + (on Windows/Linux)
  • Folding -> Collapse: ⌘ – (on macOS) / Ctrl+ – (on Windows/Linux)
  • Folding -> Expand All : ⇧ ⌘ + (on macOS) / Ctrl+Shift+ + (on Windows/Linux)
  • Folding -> Collapse All: ⇧ ⌘ + (on macOS) / Ctrl+Shift+ – (on Windows/Linux)
  • File Structure: ⌘ F12 (macOS) / Ctrl+F12 (Windows/Linux) – Twice to expand list
  • Quick documentation: F1 (macOS) / Ctrl+Q (Windows/Linux)
  • Toggle Rendered View:  ^ ⌥ Q (macOS) / Ctrl+Alt+Q (Windows/Linux)

Version Control support (Git)

  • Commit: ⌘ 0 (macOS) / Alt+0 (Windows/Linux)
  • Jump to last tool window: F12
  • Show diff: ⌘ D (macOS) / Ctrl+D (Windows/Linux)
  • Commit Anyway and Push: ⌥ ⌘ K (on macOS) / Ctrl+Alt+K (on Windows/Linux)
  • Git tool window: ⌘9 (on macOS) / Alt+9 (on Windows/Linux)
  • Terminal: ⌥ F12 (on macOS) / Alt+F12 (on Windows/Linux)
  • Git integration

Language and technology support

Integrated tools support

public static void main 🎶

On June 23, 2023 Hanno Embregts and I performed a lightning talk / pop music quiz called “public static void main 🎶 “. This was based on a Tweet that said “I realized that you can sing “public static void main” like “Everybody dance now” and I can’t stop doing it”. Hanno found 15(!!) songs that would also work, and we created a pop music quiz.

On June 23, 2023 Hanno Embregts and I performed a lightning talk / pop music quiz called “public static void main 🎶 “.

Hanno and I met at Joy of Coding 2022, where he gave his talk “What “Stairway to Heaven” Can Teach Us About Software Development“. In this talk, he plays parts of the song on stage with his travel guitar, and then explains how the lyrics are about software development.

How it started

A few weeks later, I saw a tweet that said “I realized that you can sing “public static void main” like “Everybody dance now” and I can’t stop doing it”. (And, I’ve been doing just that ever since.) Someone responded to my retweet by pointing out that this also works for Vamos a la playa.

I love it when a plan comes together

So I pitched the idea to Hanno of doing a “pop music quiz” with different songs where we would replace the lyrics with “public static void main” and we could have the audience guess what the original song was. A few months later, Hanno contacted me to say he had found at least 15(!!) songs where this would work. Apparently, he had gone through the Top 2000 looking for songs he thought might work. So we got together to discuss this idea, write an abstract and figure out where to submit it too. We submitted to several conferences that offered lightning talks slots and … got accepted to Joy of Coding 2023! Coincidentally, this is also where I got started speaking, so I was very excited to return.

Time constraints

Unfortunately, we had to cut some songs due to the 5-minute limit, so we selected the 6 we thought would work best. We selected a quiz tool, created the questions, and some videos to go with them using IntelliJ IDEA‘s live templates.
The Joy of Coding organizers were extremely helpful in allowing us to take the last slot in the lightning talk line-up, letting us use our own laptop to run the quiz, and talking to the venue to get Hanno an audio monitor at the last minute.

Joy of Coding 2023

On the day of the conference, we had a lot of fun playing and singing along.

And to our surprise, we ended up with a tie for first place! Fortunately, we had some back-up songs we could use to settle this tie in a kind of “sudden death” match between the two top contestants.

We also got some positive feedback from the crowd, as well as an invitation to perform again elsewhere.

Thanks

Many thanks to original tweeters for the idea (I’ll forgive you for also getting the song stuck in my head), Hanno Embregts for the awesome collaboration, Yosuf Haydary for pictures and videos of the event and Joy of Coding for having us!

IntelliJ IDEA: Analyzing Dependencies

If you’re working on a real world project, you’re probably using external dependencies. You might need to analyze which dependencies your application uses. For example, you may want to find out how a particular version of a dependency ended up in your application. Let’s take a look at how IntelliJ IDEA can help you to analyze dependencies.

Links

Using bots to keep our dependencies up to date

Any real world Java project will likely use external dependencies. As we’ve seen over the last few years, it’s important to keep these dependencies up to date. We used to have to manually check for updates, but fortunately these days there are tools available that can help us with this. Because, let’s be honest, most developers don’t enjoy maintaining applications. We’d much rather be using cool new tools and/or language features, and solving interesting problems. Sorry, I mean: delivering business value! But we are responsible for keeping our dependencies up to date, so let’s make that as easy as possible. In this blog post we will look at one category of tools that can help us: bots that can automatically create pull requests (PRs) to keep dependencies secure and up to date. 

For Java, we currently have three options: Dependabot, Renovate and Snyk Open Source. They each support other programming languages too, but as I mostly use Java and other JVM languages I have limited myself to these. Let’s take a look at which features they provide and their similarities and differences.

Sidenote: In order to try out and compare these bots, I’ve added them one by one to my personal GitHub profile and will describe here how to add them to your GitHub profile, as well as link to information about other integration options.

Dependabot

The first bot we will look at is Dependabot. Since Dependabot is GitHub native, we can enable most of its features from the Settings > Security > Code security and analysis. Here we can enable (or disable) the available features, and select which ones we would like to automatically enable for new repositories. 

Dependabot settings on GitHub
Dependabot settings on GitHub

Features

Dependabot offers the following features: Alerts, security updates and vulnerability updates. 

When Dependabot is enabled, it provides a Dependency Graph under the Insights tab of your project. The Dependencies tab shows any alerts to the owner of the repository. The Dependents tab shows any projects that depend on your project. In the Dependabot tab version updates can be configured.

When we enable Dependabot alerts, we will receive alerts for vulnerabilities in our repositories and we can manually generate pull requests (PRs) to resolve them. We can configure how we would like to receive these alerts. We can also view them in the Dependency Graph in the Dependencies tab.

GitHub project Insights tab with the Dependabot Dependencies graph Dependencies tab open and yellow alert stating We found potential security vulnerabilities in your dependencies.
Dependabot Dependencies graph

We can click the button to View Dependabot alerts to see more information about the alerts.

Details of Dependabot alerts on GitHub, listing several Critical updates
Dependabot alerts

Pull requests

When we enable Dependabot security updates, Dependabot will open pull requests (PRs) automatically to resolve vulnerabilities. These PRs provide information about the severity of the vulnerability, CVSS base metrics, and CVEs. We can hover over the CVSS base metrics and CVEs to get more information. We can review the changes, or dismiss the alert.

Dependabot pull request for a security update on jackson-databind with information about the vulnerabilities found.
Dependabot security update

To enable version updates, you need to add a dependabot.yml file to your repository.

Configuration

In this configuration file, you need to provide the package manager, the directory that contains your manifest file and a scheduling interval (daily, weekly, or monthly). You can configure more options, like when it should be scheduled (date, time, timezone), the maximum number of PRs (the default is 5), rebase strategy, settings that can help you manage the PRs like target branch, assignees, reviewers, commit messages and labels, and more. For more information on configuration options, see the Dependabot documentation on configuration.

Integration

While Dependabot is GitHub native, it is possible to run it locally or on GitLab too. 

Renovate 

Like Dependabot, Renovate offers security updates and version updates. In addition, Renovate will also create a project dashboard listing all updates needed on a particular project.

Renovate is available on GitHub via a GitHub app. To configure Renovate for your GitHub account, go to https://github.com/apps/renovate. Renovate allows you to set Repository access to either All repositories or Only select repositories. Renovate is the only one of these three options that allows you to try it out on only one repository first, so if you’ve never used one of these bots, I’d recommend starting with Renovate on one repository.

Install Renovate on your personal account with the option to select All repositories or Only select repositories.
Install Renovate

Renovate will create an onboarding pull request to the selected repositories. The onboarding PR contains basic configuration for Renovate to run. It describes the configuration in a Configuration Summary, and provides some information about What to Expect when the PR is merged (in this example, a list of PRs that will be opened).

Renovate onboarding PR with Configuration Summary
Renovate Onboarding PR
What to Expect section of Renovate's onboarding PR listing which PRs will be opened.
Renovate What to Expect
Renovate basic configuration
Renovate basic configuration

Note: These screenshots were taken from the PR created in September 2022. It may have changed since then.

Configuration

Renovate offers additional configuration options. In addition to setting a maximum number of PRs, Renovate allows you to to set a maximum number of concurrent branches or even an hourly limit, which can help to keep the number of open PRs and branches manageable. Renovate also lets you configure when to rebase (or not), and settings to help you manage the PRs assignees, reviewers, commit messages, labels, and more. Overall, Renovate offers more configuration options, and these options are more fine-grained than Dependabot’s options.

For more information, see the Renovate documentation on configuration options.

Once the onboarding PR is merged and the configuration file is added to your repository, Renovate will start opening pull requests with updates on the selected repositories.

Renovate pull request for jackson-databind security update
Renovate pull request

Pull requests

These PRs contain information about the reason a PR was created including which package was updated, the current and new version, as well as the following information to help you decide whether or not to merge the PR and apply the update (apart from your build being green).

  • Age: The age of the package
  • Adoption: The percentage of this package’s users (within Renovate) which are using this release
  • Passing: The percentage of updates which have passing tests for this package
  • Confidence: The confidence level for this update

For more information, see the Renovate documentation on merge confidence.

Auto merging PRs

In addition, Renovate offers the option for rule based auto merging of PRs; a feature that lets you automate upgrading dependencies. When auto merging is enabled, Renovate tries to merge the proposed update once the tests pass. Renovate recommends that you enable auto merge only for any type of dependency updates which you would just merge anyway, and keeping auto merge disabled for updates where you want to review the release notes and/or code before merging. Of course, great test coverage is also very helpful here! Renovate is currently the only of these three options that offers this feature.

Dashboards

Finally, Renovate will add a Dependency Dashboard to your project, listing all Renovate updates and detected dependencies. This dashboard can be enabled or disabled as desired. 

GitHub project Issues tab with a Renovate Dependency Dashboard link
Renovate Dependency Dashboard
Renovate project Dashboard with a list of all outdated dependencies that can be updated.
Renovate project Dashboard

In addition, Renovate provides a general dashboard with all projects & jobs run, which you can find under https://app.renovatebot.com/dashboard if you have Renovate enabled.

Integration

Note: If you are not using GitHub, Renovate currently also supports other platforms. For more information, see the Renovate documentation on supported platforms.

Snyk Open Source

Snyk Open Source is available from Snyk. There are more steps to enable it for your GitHub Profile, but it also offers more features. To enable Snyk Open Source, go to https://snyk.io/product/open-source-security-management/ and select Start free. You will need to Authorize snyk on your GitHub profile, select repository access (either Public and private repos or Public repos only), select other available features you want to use, and provide a Personal access token on GitHub.

Snyk Open Source website with the option to Start free
Snyk Open Source Start free

Features

In addition to security updates, version updates, and dashboards, Snyk Open Source offers to test for new vulnerabilities and/or test for vulnerabilities in source code. These options are currently not offered by Dependabot or Renovate. As this blog post focussed on tools to help you detect possible vulnerabilities in your dependencies and automatically create PRs to upgrade them, we will not look at scanning the source code for vulnerabilities here.

Snyk Open Source screen to Select GitHub repository access for Public and private repos or Public repos only with additional features to select
Snyk Open Source GitHub repository access and additional features

Pull requests

When enabled, Snyk Open Source will open PRs on the selected repositories. These PRs also include information about the reason for the PR, severity of a vulnerability, priority score and why it has this score, details of the version upgrade (current and new version), and more.

Snyk Open Source pull request for jackson-databind with information about the vulnerability found.
Snyk Open Source pull request

By default, Snyk Open Source will combine related updates into one single PR to help reduce the noise. Dependabot does not currently offer this option, while Renovate can be configured to do something similar.

Snyk Open Source pull request that bundles several updates.
Snyk Open Source combined PR

Snyk Open Source also has the option to test for new vulnerabilities. When enabled, incoming PRs will be checked for known vulnerabilities to make sure that no known vulnerabilities are added to the code base. Dependabot and Renovate do not currently offer this feature.

GitHub screen saying All checks have passed including a Snyk Open Source security test has passed
Snyk Open Source security test on PRs

Configuration

We can configure the frequency with which Snyk Open Source should run (daily, weekly, never). We can enable or disable scanning for new and/or known vulnerabilities, so we can clear our backlog of known vulnerabilities separately from making sure we don’t get any new vulnerabilities. This might help getting started with updating outdated dependencies without getting overwhelmed with too many updates. Dependabot and Renovate do not currently offer this option. Finally, we can also enable or disable PRs for a single project, so we can start using Snyk Open Source on a single project like we can with Renovate, but this is not a default option. 

Dashboards

The dashboards offered by Snyk Open Source are the most extensive of these three options. The dashboards provide an overview of known vulnerabilities found in your repositories with the number of vulnerabilities and their severity visible per project and overall.

Snyk Open Source Dashboard listing pending tasks and vulnerable projects and an issues summary, listing number and severity of vulnerabilities found.
Snyk Open Source Dashboard

Integration

You can use Snyk Open Source in the Snyk Web UI, with the Snyk CLI, in your IDE, or with an API. For more information, see the Snyk Open Source documentation.

Conclusion

As we have seen, the different bots offer different features. All of the options discussed here can automatically open pull requests for vulnerable dependencies and version upgrades. The information they provide with these PRs differs, as do the number and type of configuration options. Which bot is right for you will depend on needs and preferences.

Links / sources:

Managing dependencies in IntelliJ IDEA

In this tutorial, we’re going to take a look at managing dependencies in IntelliJ IDEA. We’ll look at different ways to add dependencies to your project, and how to add, upgrade and remove dependencies using Package Search.

Add dependencies

There are several ways to add new dependencies to your project.

From the build file using copy-paste

You have probably copied a dependency from Maven Repository (or another website) and pasted into your build file.

For example, we can copy the Gradle format for this dependency and paste it into our build.gradle file.

MvnRepository Gradle format

Copy dependency into build.gradle

Or, if we are using Maven, we can copy the Maven xml format into our pom.xml.

MvnRepository Maven format

Copy dependency into pom.xml

Did you know that if you copy-paste a Maven XML dependency into your build.gradle file, IntelliJ IDEA automatically turns it into the correct format for Gradle?

From the build file using code completion

We can also add dependencies to our build file using code completion. For example, let’s add a new dependency to our pom.xml.

Code completion in pom.xml

Code completion in pom.xml

Code completion in pom.xml

Code completion in pom.xml

We see that IntelliJ IDEA autocompletes the dependency xml, and we can search for the dependency we want, in this example AssertJ. If needed, the version number will also be added. Since this is a test dependency, we need to add the test scope, still using code completion.

Code completion in pom.xml

Code completion in pom.xml

Code completion works in Gradle too, as you can see below.

Code completion in build.gradle

Code completion in build.gradle

From the build file using code generation

We can also use code generation from the build file to add dependencies. In the build file, the pom.xml in a Maven project, invoke Package Search using ⌘N (on macOS) or Alt+Insert (on Windows & Linux) and in the menu that opens, select Add dependency. This will open the Dependencies tool window.

Invoke Package Search in pom.xml

Note that if we are using Gradle, we can do the same in our build.gradle file.

Invoke Package Search in build.gradle

From the Dependencies tool window

Alternatively, we can open the Dependencies tool window directly. There is no shortcut to open the Dependencies tool window, so we can either use Recent Files, ⌘E (on Mac) or Ctrl+E (on Windows/Linux), and type in “dependencies” to open the Dependencies tool window.

Recent Files Dependencies

Alternatively, we can open it by clicking Quick Launch in the bottom-left and selecting Dependencies.

Quick Launch Dependencies

In the Dependencies tool window, we can search for a dependency. For example, let’s search for AssertJ.

Search AssertJ

Note that we can select a scope for this dependency. The names of the scopes are based on the build tool with which you are working. Since this is a test dependency, and we are using Gradle in this project, we can set the scope to testImplementation.

Set Scope

We can also select the version we want to use.

Set Version

We can do the same in Maven.

Search AssertJ

Note that the names of scopes for Maven are different from Gradle. In Maven, we can set the scope for a test dependency to test.

Scope Maven

When we click Add, we see that the dependency is added to the build file.

Add AssertJ

If the version number is shown in red, that means IntelliJ IDEA hasn’t downloaded this library before. Click Load Maven Changes so IntelliJ IDEA will update its dependencies based on the changes to the pom.xml or build.gradle file.

Go back to the Dependencies tool window and clear the search box by clicking the x on the right-hand side. You’ll see the project’s dependencies are updated with your new dependency.

Next, let’s look for jackson-databind. We see that there are several versions available. Since we have selected Only stable, only stable versions are shown in the list.

Jackson-Databind Versions

If we uncheck this option, we see that the list of versions also includes the release candidates.

Jackson-Databind Only Stable Versions

For production code, we probably want to use stable versions, so let’s select the Only stable checkbox again. With this option enabled, IntelliJ IDEA will exclude any dependencies that have no stable versions, and hide them from the list. Now we can select the latest stable version and add this to our project. Let’s also Load Maven Changes again.

Finally, let’s also add a new dependency to the Kotlin module. Let’s switch to the Kotlin module and open the pom.xml for this module. Open the Dependencies Tool Window and search for Ktor.

Search Ktor

Notice that some dependencies are marked as Multiplatform.

Show Kotlin Multiplatform

If we want to see only Kotlin multiplatform dependencies, we can select the Kotlin multiplatform checkbox, as shown below.

Select Kotlin Multiplatform

When we click Add to the right of the Ktor dependency, we see that Ktor is added to the list of dependencies and to the pom.xml for the Kotlin module.

Add Ktor

Upgrade dependencies

We will also need to keep our dependencies up to date. To show you how IntelliJ IDEA can help, we are using this extremely outdated project as an example. In the pom.xml below, we see that several dependencies are marked with squiggly lines underneath them.

Outdated Dependencies in pom.xml

IntelliJ IDEA will show the suggestion to upgrade when we hover over the dependency, and we can click the suggestion to upgrade the dependencies.

Hover over outdated dependency

Alternatively, we can use Context Actions ⌥⏎ (on macOS) or Alt+Enter (on Windows & Linux) to upgrade these dependencies.

Context Actions

We can also upgrade our dependencies using the Dependencies tool window. The Dependencies tool window will tell us if there’s a newer version of a dependency, as we can see here.

Dependencies with newer versions

We can choose the version to upgrade to by clicking on the version number in the list. Note that we don’t have to use the latest version.

Select version

We can also automatically upgrade a dependency to the latest version by clicking Upgrade for that particular dependency.

Upgrade individual dependency

Or, we can even upgrade all our dependencies at once, by clicking the Upgrade all link.

Upgrade all dependencies

Remove dependencies

Finally, we can remove dependencies we no longer need. In the Dependencies tool window, let’s remove jackson-databind from the Java module. We select the dependency we want to remove (jackson-databind) and in the Dependency details pane on the right, click the More button (three dots) and select Remove.

Remove Dependency

We will see that the dependency is removed from the pom.xml and the dependency list. To remove a dependency from the whole project, select All Modules on the left.

Summary and Shortcuts

Now we know the different ways in which we can view our project’s dependencies in IntelliJ IDEA, and the different focus for each view.

IntelliJ IDEA Shortcuts Used

Here are the IntelliJ IDEA shortcuts that we used.

NamemacOS ShortcutWindows / Linux Shortcut
Open / Close Project Tool Window⌘1Alt+1
Recent Files⌘EControl+E
Invoke Package Search⌘NAlt+Insert
Context Actions⌥⏎Alt+Enter
Shortcuts used

Related Links

IntelliJ IDEA: Managing Dependencies

In this screencast, we’re going to take a look at managing dependencies in IntelliJ IDEA. We’ll look at different ways to add dependencies to your project, and how to add, update and remove dependencies using Package Search.

Related Links

Pair programming in Java with an 8 year old

Recently I asked my 8 year old if he would be interested in doing some Java programming with me, and he was. This was such a fun experience, I wanted to share it with you.

Why Java?

In the past, we have done part of a Scratch course by Felienne. So I know there are other programming languages out there that are made specifically for kids. However, I wanted to show him something that is a bit more like what his dad (also a software developer) and I do all day.

It was an explicit decision on my part not to bore him with Java syntax just yet, but instead to focus on what the program should do and getting a bit of understanding of how programming works. While most of the code was written by me, the behavior of our little application was based on our collective ideas.

Hello world!

We used IntelliJ IDEA Community Edition 2022.3, and I opened a new project using Java and Maven, thinking we would get started with a simple Hello World program (as you do).

New Project wizard in IntelliJ IDEA with Java and Maven selected, as well as JDK temurin-17
New Project wizard

It turned out that IntelliJ IDEA already includes the Hello World example when opening a new project, which was a nice surprise.

Hello world! program in Java
Hello world!

First, I asked him to run the program by clicking the run button (green triangle) in the gutter. He asked me what it means to “run” the program, so I explained this means having the computer execute the program, doing the thing the code tells it to do.

When we ran the program, we saw that the text “Hello world!” was printed in the command line. I tried explaining that “public static void main” is the main method, telling the computer where to start, but to be honest I’m not sure he understood that just yet.

Asking for user input

Next, I asked him whether he would like to print something else and what we would need to change in order to do so. He knew we had to change the green text (the String) to something else. He changed the word “world” in this String to his name and ran the program again.

My next suggestion was to ask the user for their name so the computer would be able to greet other people too. Here I briefly explained we would need some way to capture the user’s input. To do so, I added a Scanner and the variable “name”. After I made these changes, he ran the program and tested that it worked when he input his name.

A simple Java program using Scanner to output a question, capture the input and print the result
Asking for user’s name

Next, we discussed what else to ask the user. He wanted to ask for their favorite color and provide the “computer’s” favorite color as a response to their answer. We added another question and captured another variable to return to the user.

A simple Java program using Scanner to output a question, capture the input and print the result
Asking for name and favorite color

Selecting a language

Of course, while the kids speak some English, it is not their native language. So we decided to translate the output to Dutch to make it a little easier for him to understand. Next, he suggested we should give the user the option of using the program either in Dutch or in English. We started with a simple if/else statement and duplicated code blocks of asking the same questions in either Dutch or English, depending on the input.

A Java programming using an if/else statement to select a language
Selecting a language

He was quick to point out that we should think about what to do if the user provided a language or input we didn’t know. Good question! So we proceeded to add logic for that as well.

A Java program checking that input is a valid option before proceding.
Validate input

Next, we ran the program several times to check that it worked for each valid option, as well as (multiple) invalid options.

Next steps

Finally, we discussed what potential next steps we could take with this program. We had several ideas:

  • He wanted to know if it would be possible to remove the duplication somehow; for example, by getting the Dutch or English text from somewhere so we wouldn’t have to duplicate all the code. In our current program, the code for the Dutch version and English version is duplicated, meaning that for every additional question we want to ask the user, we have to make sure to duplicate that.
  • In one of my tests, I showed him that the computer would just capture and return whatever the user’s input was. The example I used was to answer “Hello, what is your name?” with a full sentence: “Hi, my name is Marit” to which the computer would reply “Hello Hi, my name is Marit, what is your favorite color?” which is a bit weird. So that is something to think about.

Takeaways

The most important thing is that we had fun. He was motivated to add new things to the program and to test that they worked. My choice to not focus on the details of Java syntax, but on the general program instead seems to have worked because he had fun and wanted to continue. He is already asking me when we can do this again, and has ideas of what we could do next.

The program was written based on his ideas and he did write some of it himself, mainly the Strings and some of the “System.out.println()” lines, after I showed him how to use IntelliJ IDEA live templates to do so; if you type “sout” and press Enter (or Return on Mac), IntelliJ IDEA will expand that to “System.out.println()” which he thought was very helpful.

What I noticed was that he was able to think about what the program should do, and had a rough understanding of how the code worked. Once we were done, he was able to explain our little program to his dad, and pointing to the relevant points in the code while explaining what they did. So I have the impression he has some understanding of how it works.

Overall, we had fun together coding and it was awesome to see how his mind worked when thinking about what the program should do and how, and how to test it. We are very much looking forward to continuing our little experiment.

Our code can be found on GitHub.