Here’s a type that has been around in the JDK for a while and that comes in handy when we want to define maps with enum types as keys: An EnumMap is a such as specialized Map.
We’ll create a map for a given enum:
public enum CoffeeType {
ESPRESSO, POUR_OVER, FRENCH_PRESS
}The EnumMap needs to be aware of the enum class at creation time:
Map<CoffeeType, String> favoriteCoffeeOrigins = new EnumMap<>(CoffeeType.class);
favoriteCoffeeOrigins.put(CoffeeType.ESPRESSO, "Ethiopia");
favoriteCoffeeOrigins.put(CoffeeType.POUR_OVER, "Colombia");
favoriteCoffeeOrigins.put(CoffeeType.FRENCH_PRESS, "Indonesia");
assertThat(favoriteCoffeeOrigins.get(CoffeeType.ESPRESSO)).isEqualTo("Ethiopia");An EnumMap is much more efficient compared to a HashMap implementation. All basic map operations of this Java implementation are executed in constant time.
This post was reposted from my newsletter issue 017.
| Published on Java Code Geeks with permission by Sebastian Daschner, partner at our JCG program. See the original article here: Mapping enum keys with EnumMaps Opinions expressed by Java Code Geeks contributors are their own. |
