NestedOptionals

WARNING

FragileCode

Summary

Avoid nesting Optionals inside Optionals; the resultant code is hard to reason about

Suppression

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

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

Samples

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.Optional;
import java.util.stream.Stream;

class A {
  void m() {
    Optional.empty();
    Optional.of(1);
    // BUG: Diagnostic contains:
    Optional.of(Optional.empty());
    // BUG: Diagnostic contains:
    Optional.of(Optional.of(1));

    Optional.ofNullable(null);
    // BUG: Diagnostic contains:
    Optional.ofNullable((Optional) null);

    Optional.of("foo").map(String::length);
    // BUG: Diagnostic contains:
    Optional.of("foo").map(Optional::of);

    Stream.of("foo").findFirst();
    // BUG: Diagnostic contains:
    Stream.of("foo").map(Optional::of).findFirst();
  }
}

import java.time.Duration;

class A {
  void m() {
    Duration.ofSeconds(1);
  }
}