IntelliJ IDEA supports new Java versions from day one. Several features were added to make working with Java 25 language features in IntelliJ IDEA easier.

New project

Create a new project in IntelliJ IDEA.

You can use the New Project Wizard to create a new project in IntelliJ IDEA. If you select the option to Add sample code, IntelliJ IDEA will add sample code to your project, containing a class with a main method.

If you select IntelliJ as your Build system, set JDK to 25, the sample code will be a compact source file and instance main method, introduced in Java 25.

Compact source file

Create a compact source file in IntelliJ IDEA.

Compact source files were introduced in Java 25. To create a compact source file, right-click the Project tool window (or press ⌘N (macOS) / Alt+Ins (Windows/Linux)) and select New | Java Class. In the New Java Class popup, select the option Compact source file.

This compact source file is created in the root directory of your project, even if you create it from another package. IntelliJ IDEA automatically adds an instance main method void main() to the file.

Java Compact File

Create a compact source file in IntelliJ IDEA.

To create a Java Compact File, introduced in Java 25, right-click the src/main/java directory in the Project tool window and select New | Java Compact File. IntelliJ IDEA will provide a default name for the file, so your thought process is not disrupted when you want to quickly try something out. IntelliJ IDEA automatically adds an instance main method void main() to the file.

Convert compact source file to class

Convert a compact source file to a class in IntelliJ IDEA.

Java 25 introduced the concept of implicit classes or compact source files. We can convert an implicit class to a regular class as needed. Invoke Context Actions by pressing ⌥⏎ (macOS) / Alt+Enter (Windows/Linux) and select Convert an implicitly declared class of a compact source file into a regular class.

The reverse is also possible, should you prefer to use an implicit class at any point. To do so, use the quick-fix Convert into compact source file.

New live templates for main methods

Create an instance main method using a live template.

IntelliJ IDEA has some new live templates to add a main method to an implicit class, either with or without arguments: main, maina, psvm, psvma. Using the live templates psvm or main inside a compact source file will add the new main method, while they will continue to add the classic main method inside a class, as you can see in the preview.

Add arguments

Add args to your main method.

The new void main() method, introduced in Java 25, does not need String[] args. However, should you decide to use the args in your code, IntelliJ IDEA will help you by also adding them to the main method. Type args and press ⏎ (macOS) / Enter (Windows/Linux) to select args from code completion.

Live templates for simple IO

Add simple IO methods using live templates.

Java 25 introduces simple IO methods, such as IO.println() and readln() to make interacting with the console more convenient. IntelliJ IDEA introduces two new live templates to use these methods: iop for println() and ior for readln().

In addition, there are quick-fixes available to convert IO.println() to System.out.println(), and vice versa. Invoke Context Actions ⌥⏎ (macOS) / Alt+Enter (Windows/Linux) on the method and select the option Replace with System.out.println() or Replace with IO.println().

Add static import for simple IO

Add a static import for simple IO methods.

Java 25 introduces simple IO methods, such as IO.println() and readln() to make interacting with the console more convenient. To use these methods in a compact source file, you don’t need to add an import. However, you can add a static import the java.lang.IO class if you prefer. Invoke Context Actions ⌥⏎ (macOS) / Alt+Enter (Windows/Linux) on the method and select the option Add on-demand static import for java.lang.io.

Module Import

Using module import in IntelliJ IDEA.

Java 25 introduces module imports. When adding a module import, use Jump Down to see the contents of the module. When using Optimized Imports, IntelliJ IDEA will automatically remove any imports that are added by the module import. If you prefer to use single class imports, invoke Context Actions ⌥⏎ (macOS) / Alt+Enter (Windows/Linux) and select Replace with single class imports.

If desired, it is possible to delete unused module imports when using Optimized Imports. To configure this option, open Settings | Editor | Code Style | Java and go to the Imports tab. Select the option Delete unused module imports. When this option is selected, Optimized Imports will remove unused module imports.

Conclusion

Support for Java language features in IntelliJ IDEA makes it easy to adopt and work with new Java language versions.

Recently my friend Piotr posted a question on social media about how to format records in IntelliJ IDEA…

Sidenote: I don’t know why he wouldn’t just ask me directly, but I guess this was more fun 😉

Configuring code style

IntelliJ IDEA can format your code for you. Code will be formatted as you type it, and if needed you can Reformat the code (⌘⌥L on macOS) / Ctrl+Alt+L on Windows/Linux). If the (pre)defined code style isn’t to your liking, you can change it.

By default, IntelliJ IDEA will format records with the curly braces {} on two lines. When you apply Reformat to a record, IntelliJ IDEA will let you know “No lines changed: content is already properly formatted”.

To change the formatting for records so that the curly braces {} will be on the same line, open Settings (⌘, on macOS / Ctrl+Alt+S on Windows/Linux) and go to Editor | Code style | Java. Open the tab Wrapping and Braces and in the section Keep when reformatting select the option Simple classes in one line. Don’t forget to Save Changes.

Now if we have any code with a record (or any other simple class), we can use the Reformat the code (⌘⌥L on macOS) / Ctrl+Alt+L on Windows/Linux) to reformat the simple class accordingly. Note that you’ll need to use the shortcut twice to remove custom line breaks.

The same formatting will be applied in other situations. For example, when we add another record to the file, and use Complete Current Statement (⌃⇧⏎ on macOS / Ctrl+Shift+Enter on Windows/Linux), our new record will be completed with the curly braces {} on one line. 

What about generating a new Record?

From the Project tool window, we can generate a new record. Use Generate New (⌘N  on macOS / Alt+Ins on Windows/Linux) and select Java class. In the New Java Class dialog, type the name of your new record, and select Record. Note this record is still generated with the curly braces {} on 2 lines.

To make sure a newly created record is also formatted with the curly braces {} on one line, we can change the File template for Record.

Open Settings (⌘, on macOS / Ctrl+Alt+S on Windows/Linux) and go to Editor | Code style | File and Code Templates. Open the template for Record and change the template to have the curly braces {} on one line. Again, don’t forget to Save Changes.

Now when we generate a new record it will be formatted with the curly braces {} on one line.

Note that changing only the File Template for Record is not enough to format records with the curly braces {} on one line. For one, it will be immediately reformatted upon creation according to the code style, as long as the Reformat according to style box is checked for this file template. Even if we uncheck this option, reformatting a file with a record would reformat it to the code style (which by default is {} on 2 lines).

Links

• IntelliJ IDEA Code Style (documentation)