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Class explicitly extends a 'Collection' class

Reports classes that extend concrete subclasses of the java.util.Collection or java.util.Map classes.

Subclassing concrete collection types is a common yet poor practice. It is considerably more brittle than delegating collection calls.

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.

ClassExtendsConcreteCollection
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.

Settings or Preferences | Editor | Inspections | Java | Inheritance issues

Inspection ID: ExtendsConcreteCollection

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 ClassExtendsConcreteCollection

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

Inspection Details

By default bundled with:

IntelliJ IDEA 2025.3, Qodana for JVM 2025.3,

Last modified: 03 December 2025