Method or constructor references are more readable than lambda expressions in many situations, and may therefore be preferred.
However, method references are sometimes less concise than lambdas. In such cases, it might be preferrable to keep the lambda expression for better readability. Therefore, this rule only raises issues on lambda expressions where the replacement method reference is shorter.
This rule is automatically disabled when the project’s sonar.java.source
is lower than 8
, as lambda expressions were
introduced in Java 8.
Refer to the called method by its reference instead of wrapping it in a lambda expression.
For instance:
null
checks can be replaced with references to Objects::isNull
and Objects::nonNull
SomeClass.class::cast
instanceof
can be replaced with SomeClass.class::isInstance
class A { void process(List<A> list) { list.stream() .filter(myListValue -> myListValue instanceof B) // Noncompliant .map(listValueToMap -> (B) listValueToMap) // Noncompliant .map(bValueToMap -> bValueToMap.<String>getObject()) // Noncompliant .forEach(o -> System.out.println(o)); // Noncompliant } } class B extends A { <T> T getObject() { return null; } }
class A { void process(List<A> list) { list.stream() .filter(B.class::isInstance) // Compliant .map(B.class::cast) // Compliant .map(B::<String>getObject) // Compliant .forEach(System.out::println); // Compliant } } class B extends A { <T> T getObject() { return null; } }