Anonymous type can be replaced with lambda

Reports anonymous classes which can be replaced with lambda expressions.

Example:

  new Thread(new Runnable() {
    @Override
    public void run() {
      // run thread
    }
  });

After the quick-fix is applied:

  new Thread(() -> {
    // run thread
  });

Note that if an anonymous class is converted into a stateless lambda, the same lambda object can be reused by Java runtime during subsequent invocations. On the other hand, when an anonymous class is used, separate objects are created every time. Thus, applying the quick-fix can cause the semantics change in rare cases, e.g. when anonymous class instances are used as HashMap keys.

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.

Convert2Lambda

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.

Use the Report when interface is not annotated with @FunctionalInterface option to ignore the cases in which an anonymous class implements an interface without @FunctionalInterface annotation.

This inspection depends on the Java feature 'Lambda expressions', which is available since Java 8.

Inspection options

Here you can find the description of settings available for the Anonymous type can be replaced with lambda inspection, and the reference of their default values.

Report when interface is not annotated with @FunctionalInterface: Default: Selected

Inspection Details
By default bundled with:	IntelliJ IDEA 2024.3, Qodana for JVM 2024.3,
Can be installed with plugin:	Java, 243.26483

01 April 2025