java11-enum-clean-code

Overview of how to to construct modern enums using lambda.

enum compliation

• https://stackoverflow.com/questions/32354107/how-are-enums-internally-represented-in-java
• only syntactic sugar

public enum Ordinals {
    FIRST("st"),
    SECOND("nd"),
    THIRD("rd");
    private String notation;
    private Ordinals(String notation) {
        this.notation = notation;
    }
    public String getNotation() {
        return notation;
    }
}

public final class Ordinals extends java.lang.Enum<Ordinals> {
  public static final Ordinals FIRST;

  public static final Ordinals SECOND;

  public static final Ordinals THIRD;

  private String notation;

  private static final Ordinals[] $VALUES;

  public static Ordinals[] values() {
      return $VALUES.clone();
  }

  public static Ordinals valueOf(String name) {
      return (Ordinals) Enum.valueOf(Ordinals.class, name);
  }

  private Ordinals(String name, int ordinal, String notation) {
      super(name, ordinal);
      this.notation = notation
  }

  static {
      FIRST = new Ordinals("FIRST", 0, "st");
      SECOND = new Ordinals("SECOND", 1, "nd");
      THIRD = new Ordinals("THIRD", 2, "rd");
      Ordinals[] $VALUES = new Ordinals[3];
      $VALUES[0] = FIRST;
      $VALUES[1] = SECOND;
      $VALUES[2] = THIRD;
      Ordinals.$VALUES = $VALUES;
  }
}

project description

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));
}