IsInstanceLambdaUsage

SUGGESTION

Simplification

View source code on GitHub

Summary

Prefer Class::isInstance method reference over equivalent lambda expression

Suppression

Suppress false positives by adding the suppression annotation @SuppressWarnings("IsInstanceLambdaUsage") to the enclosing element.

Disable this pattern completely by adding -Xep:IsInstanceLambdaUsage:OFF as compiler argument. Learn more.

Samples

Replacement

Shows the difference in example code before and after the bug pattern is applied.

 import java.util.stream.Stream;
 
 class A {
   void m() {
-    Stream.of(1).filter(i -> i instanceof Integer);
+    Stream.of(1).filter(Integer.class::isInstance);
   }
 }
 

Identification

Shows code lines which will (not) be flagged by this bug pattern.
A //BUG: Diagnostic contains: comment is placed above any violating line.

import java.util.stream.Stream;
import reactor.core.publisher.Flux;

class A {
  void m() {
    Integer localVariable = 0;

    Stream.of(0).map(i -> i);
    Stream.of(1).map(i -> i + 1);
    Stream.of(2).filter(Integer.class::isInstance);
    Stream.of(3).filter(i -> i.getClass() instanceof Class);
    Stream.of(4).filter(i -> localVariable instanceof Integer);
    // XXX: Ideally this case is also flagged. Pick this up in the context of merging the
    // `IsInstanceLambdaUsage` and `MethodReferenceUsage` checks, or introduce a separate check that
    // simplifies unnecessary block lambda expressions.
    Stream.of(5)
        .filter(
            i -> {
              return i instanceof Integer;
            });
    Flux.just(6, "foo").distinctUntilChanged(v -> v, (a, b) -> a instanceof Integer);

    // BUG: Diagnostic contains:
    Stream.of(7).filter(i -> i instanceof Integer);
  }
}