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Java 8 - Functions - Composition





  • Often it makes sense to chain functions, such that the output of a function is fed into another function.
  • fncB(fncA) can be implemented using 'andThen' and 'compose' keywords.
  • apply fncA andThen apply fncB, i.e. fncA.andThen(fncB)
  • apply fncB but first compose fncA i.e. fnB.compose(fncA)


@Slf4j
public class FunctionComposition {

   static Function<Person, String> eat = person -> person.getFirstName() + " is eating";

   static Function<String, String> personStatus = UnaryOperator.identity();

   public static void main(String[] args) {

     Person person = new Person("Tom", "Cruise");

     log.info("andThen: " + eat.andThen(personStatus).apply(person));
     log.info("compose: " + personStatus.compose(eat).apply(person));

   }
}



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