Call of Java mutator method on immutable Kotlin collection

Reports Java mutator methods calls (like fill, reverse, shuffle, sort) on an immutable Kotlin collection.

This can lead to UnsupportedOperationException at runtime.

Example:

  import java.util.Collections

  fun test() {
      val immutableList = listOf(1, 2)
      Collections.reverse(immutableList)
  }

To fix the problem make the list mutable.

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.

JavaCollectionsStaticMethodOnImmutableList

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 | Kotlin | Java interop issues

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 JavaCollectionsStaticMethodOnImmutableList

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