Redundant usage of unmodifiable collection wrappers

Reports redundant calls to unmodifiable collection wrappers from the Collections class.

If the argument that is passed to an unmodifiable collection wrapper is already immutable, such a wrapping becomes redundant.

Example:

  List<String> x = Collections.unmodifiableList(Collections.singletonList("abc"));

After the quick-fix is applied:

List<String> x = Collections.singletonList("abc");

In order to detect the methods that return unmodifiable collections, the inspection uses the org.jetbrains.annotations.Unmodifiable and org.jetbrains.annotations.UnmodifiableView annotations. Use them to extend the inspection to your own unmodifiable collection wrappers.

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.

RedundantUnmodifiable

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 | Verbose or redundant code constructs

New in 2020.3

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 RedundantUnmodifiable

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

IntelliJ IDEA 2025.2

Inspection Details
By default bundled with:	IntelliJ IDEA 2025.2, Qodana for JVM 2025.2,

Last modified: 18 September 2025