Overview of how to to construct modern enums using lambda.

We have enum JobTitle

public enum JobTitle {
    PRESIDENT, VICE_PRESIDENT, OFFICER, MANAGER, DEVELOPER,
    CONSULTANT, IMPLEMENTATION_OFFICER, INTERN;
}

and groups:

• administration:

  private static ImmutableSet<JobTitle> ADMINISTRATION =
              ImmutableSet.of(PRESIDENT, VICE_PRESIDENT);
  

• operational:

  private static ImmutableSet<JobTitle> OPERATIONAL =
          ImmutableSet.of(MANAGER, OFFICER);    
  

• it is a good practice to provide static methods that return predicates:

  public static Predicate<JobTitle> administration() {
      return JobTitle::isAdministration;
  }
  
  public static Predicate<JobTitle> operational() {
      return JobTitle::isOperational;
  }
  

  where, obviously:

  public boolean isAdministration() {
      return ADMINISTRATION.contains(this);
  }
  
  public boolean isOperational() {
      return OPERATIONAL.contains(this);
  }
  

• and a stream() method:

  public static Stream<JobTitle> stream() {
          return Arrays.stream(values());
  }
  

because later in the code it's easy to write very expressive code (like in JobTitleTest):

@Test
public void isBusinessShowcase() {
    JobTitle.stream()
            .filter(administration().or(operational()))
            .forEach(title -> System.out.println("Performed action for: " + title));
}