Mapping enum values by its name

Question

I am trying to map all the values ​​of this enum by its componentType. unfortunately I don't know how to map it with the array, tried using toImmutableMap (v-> v.componentType, v-> v) but this only work with a ImmutableMap<String, MatchType> and i need map it as array (MatchType[]), can someone tell me how i can do that or if there is a better way?

ImmutableMap<String, MatchType[]> findByComponentType = Arrays.stream(MatchType.values()).collect(toImmutableMap(v -> /** what to put here */));

Example: If i use findByComponentType.get("android.support.v4.app.Fragment") it should return SUPPORT_FRAGMENT & SUPPORT_FRAGMENT_PRE_API23.

 private enum MatchType {
  ACTIVITY(
      "android.app.Activity",
      "onCreate",
  FRAMEWORK_FRAGMENT(
      "android.app.Fragment",
      "onAttach",
  FRAMEWORK_FRAGMENT_PRE_API23(
      "android.app.Fragment",
      "onAttach",,
  SUPPORT_FRAGMENT(
      "android.support.v4.app.Fragment",
      "onAttach",
  SUPPORT_FRAGMENT_PRE_API23(
      "android.support.v4.app.Fragment",
      "onAttach");

  MatchType(String componentType, String lifecycleMethod) 

Answer 1

Instead of ImmutableMap<String, MatchType[]> you really want ImmutableMultimap (ImmutableSetMultimap specifically because your values would be enum value suitable for set instead of array/list).

Create your reverse mapping like this:

private static final ImmutableSetMultimap<String, MatchType> COMPONENT_TYPE_LOOKUP =
        EnumSet.allOf(MatchType.class).stream()
                .collect(toImmutableSetMultimap(
                        matchType -> matchType.componentType, // or MatchType::getComponentType if there's a getter,
                        matchType -> matchType                // or Function.identity()
                ));

And then you'd have

static Set<MatchType> findByComponentType(String componentType) {
    return COMPONENT_TYPE_LOOKUP.get(componentType);
}

and in the end it'll return a set of matching types:

@Test
public void shouldMatchType() {
    final Set<MatchType> types = findByComponentType("android.support.v4.app.Fragment");
    assertThat(types)
            .containsExactlyInAnyOrder(MatchType.SUPPORT_FRAGMENT,
                                       MatchType.SUPPORT_FRAGMENT_PRE_API23);