Compact source file can be replaced with a regular class

Reports compact source files and suggests replacing them with regular classes.

Example (in file Sample.java):

  void main() {
      String a = "Hello, world!";
  }

After the quick-fix is applied:

public class Sample {
    void main() {
        String a = "Hello, world!";
    }
}

Locating this inspection

By ID

Can be used to locate inspection in e.g. Qodana configuration files, where you can quickly enable or disable it, or adjust its settings.

ImplicitToExplicitClassBackwardMigration

Via Settings dialog

Path to the inspection settings via IntelliJ Platform IDE Settings dialog, when you need to adjust inspection settings directly from your IDE.

This inspection can help to downgrade for backward compatibility with earlier Java versions.

This inspection depends on the Java feature 'Compact source files', which is available since Java 21-preview.

Inspection ID: ImplicitToExplicitClassBackwardMigration

New in 2024.1

Suppressing Inspection

You can suppress this inspection by placing the following comment marker before the code fragment where you no longer want messages from this inspection to appear:

//noinspection ImplicitToExplicitClassBackwardMigration

More detailed instructions as well as other ways and options that you have can be found in the product documentation:

IntelliJ IDEA 2025.3

Inspection Details
By default bundled with:	IntelliJ IDEA 2025.3, Qodana for JVM 2025.3,

Last modified: 03 December 2025