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));
}