[FIXED] JavaFX and IntelliJ no errors althought the documentation says I should have some

Issue

I'm currently following this tutorial: https://openjfx.io/openjfx-docs/ (JavaFX and IntelliJ IDEA). I use Intellij 2021.3.2.

I have created a project (1. Create a JavaFX project), which worked out great and didn't need to 2. Set JDK 16 because it was already set to 17 (which I guess is fine).

But here begin the weird stuff (and I'm very new to programming so I'm sorry if it sounds silly). "You can also set the language level to 11 or greater." I don't have this option. Because it's "can" I felt like it wasn't a big deal but if someone can explain what this is all about? Just out of curiosity, because I'm at the very beginning of the tutorial and I kinda only understand half of it.

Then 3. Create a library, and I don't have what they have, and my stuff is red:

So when they said "add the JavaFX 17 SDK as a library to the project" I didn't know what to do. I also didn't know what to do to fix the red stuff.

And finally, they say "Warning: If you run now the project it will compile but you will get this error: ..." but if I click on this button

everything works! which you know i'm not complaining about but I would like to understand a bit more what is happening.

And then they suggest I should 4. Add VM options to fix the problem that I don't have. So I figured maybe my computer set the VM options correctly without me knowing it but there is currently no VM option (and it works). Should I add them nonetheless?

Thank you for your help, I'm very lost and feel like I don't really understand anything.

Solution

The current documentation in the openjfx tutorial for getting started with JavaFX using Idea is incorrect, at least for recent Idea releases (2021.3 +).

The tutorial is written as though a new Java project was created, rather than a new JavaFX project. Once a new JavaFX project has been created, most of the rest of the steps in the tutorial are either redundant or wrong.

Step 1, “Create a JavaFX project", does a lot more than just “Create a Java project”, which is why everything else is different from the tutorial.

A better tutorial for getting started with JavaFX with Idea, is the official Idea documentation:

• Create a new JavaFX project.

Differences between creating a new Java project and creating a new JavaFX project

The new JavaFX project:

1. Provides a build script for Maven (pom.xml) or Gradle (build.gradle).

2. Adds the appropriate dependencies for JavaFX base, graphics, controls and fxml.

3. Provides an example application and controller code that you can run immediately.

4. The example project is modular and provides a module-info.java

5. Because the program is modular and dependencies are downloaded via maven and recognized by the IDE, you don’t need to manually configure VM runtime options for the module path and adding modules.

6. Idea will recognize the Maven or Gradle projects and automatically synchronize the initial transitive dependent libraries with the Idea project.

7. There are options in the Idea Maven tool window which will allow you to synchronize further changes to dependent libraries or javadoc and source code in libraries.

8. Selects a JDK and attaches it to the project, automatically downloading the selected JDK version if not already present.

9. Sets an appropriate language level for the project.

When you just use the create new Java Project option, it doesn’t do any of those things, so you need to do things manually instead, which is what the rest of that tutorial is about:

1. Manually download the JDK and configure it in the SDK.

2. Manually download the JavaFX SDK and add the libraries from it to your project.

3. Manually configure VM modular arguments.

4. Manually maintain any other dependencies.

5. Manually associate javadoc and source code.

6. Manually write the code for a basic application.

7. Manually set the project language level.

Doing all this stuff manually is more work and more error prone. The manual work usually leads to a worse outcome and a project that is more difficult to maintain for many people getting started with JavaFX, so I do not recommend it.

Versions

In terms of the versions to use, I recommend using the most recent stable (non-beta) releases of both JDK and JavaFX, regardless of what versions may be referenced in any tutorials you may be using.

You can set JavaFX versions in the Maven file generated by the new JavaFX project wizard, then press the button in the Maven Tool window to synchronize the Maven project with the Idea project.

Language level settings

These are important later on, but pretty irrelevant when just getting started.

The language level settings:

1. Tell the compiler what version of the java byte code to compile the application to.

2. Tell the IDE what language syntax rules to enforce and provide help with.

If you use Java 17 only features, the app won’t run on a Java 11 VM.

You can define the settings in Idea manually:

• language setting level.

But it is better to set them in the compiler section of the maven project and synchronize the project with Idea, which will also configure the settings in the IDE.

IMO, set it to the most recent stable version and have a requirement that your application be run with that Java version as a minimum (you can enforce that by using jlink or jpackage to bundle the JRE version you choose with your packaged app).

Answered By - jewelsea
Answer Checked By - Timothy Miller (JavaFixing Admin)