immutables

A library for creating and using immutable Java beans.

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/* Type definition for an "Immutable Type". */
public static class AnimalType extends LazyImmutableType {
    /* Define a type inside of itself. */
    private static final AnimalType ANIMAL_TYPE = Immutables.def(AnimalType.class);

    //Define the fields.
    public final ImmutableField<String> name = ImmutableField.of(String.class);
    public final ImmutableField<Integer> populationCount = ImmutableField.of(Integer.class);
    public final ImmutableField<Integer> legs = ImmutableField.of(Integer.class);

    //We can add validation.
    public final FieldValidation<String> nameUppercase = FieldValidation.on(name,
        v -> {
            if (v.toUpperCase().equals(v)) {
                return Optional.empty();
            }
            return Optional.of("Name must be upper case.");
        }
    );


    public AnimalType () {
        autoDefine();
    }

    /* Re-usable populator based on the fields defined in AnimalType. */
    public State populate (State state) {
        return state
            .populator()
            .set(name, "Lion")
            .set(legs, 0)
            .set(populationCount, 1)
            .done();
    }

    /**
     * A quick way to get the type definition.
     * @return The type.
     */
    public static final AnimalType type() {
        return ANIMAL_TYPE;
    }

};