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.

Lambda syntax is not supported in Java 1.7 and earlier JVMs.

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.

Inspection options

Option	Type	Default
Report when interface is not annotated with @FunctionalInterface	Checkbox	true

Inspection Details
Available in:	IntelliJ IDEA 2023.3, Qodana for JVM 2023.3
Plugin:	Java, 233.SNAPSHOT

Last modified: 13 July 2023