Overview of how to to construct modern enums using lambda.
- 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; } } 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)); }