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Cleaner captures object reference

Reports Runnable passed to a Cleaner.register() capturing reference being registered. If the reference is captured, it will never be phantom reachable and the cleaning action will never be invoked.

Possible sources of this problem:

  • Lambda using non-static methods, fields, or this itself

  • Non-static inner class (anonymous or not) always captures this reference in java up to 18 version

  • Instance method reference

  • Access to outer class non-static members from non-static inner class

Locating this inspection


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

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 | Probable bugs

Sample of code that will be reported:

int fileDescriptor; Cleaner.Cleanable cleanable = Cleaner.create().register(this, () -> { System.out.println("adsad"); //this is captured via fileDescriptor fileDescriptor = 0; });

This inspection only reports if the language level of the project or module is 9 or higher.

New in 2018.1


By default bundled with

IntelliJ IDEA 2024.1, Qodana for JVM 2024.1,

Can be installed with plugin

Java, 241.18072

Last modified: 18 June 2024