java - How to access an unknown enum's "valueOf()" method

Question

I have configuration files which can be populated with enums and their respective values and will then be read by my program.

For example, a configuration file (yaml format) may look like this:

SomeEnumClass:
- VALUE_A_OF_SOME_ENUM
- VALUE_B_OF_SOME_ENUM
- ANOTHER_VALUE

AnotherEnumClass:
- VALUE_1
- VALUE_3
- VALUE_3
- VALUE_7
[etc...]

Unfortunately this leads to duplication in my code (java) like this:

if (enumNameString.equals("SomeEnumClass")) {
    Collection<SomeEnumClass> values = new ArrayList<>;
    for (String listEntry : yamlConfig.getStringList(enumNameString)) {
        values.add(SomeEnumClass.valueOf(listEntry));
    }
    return values;

} else if (enumNameString.equals("AnotherEnumClass")) {
    Collection<AnotherEnumClass> values = new ArrayList<>;
    for (String listEntry : yamlConfig.getStringList(enumNameString)) {
        values.add(AnotherEnumClass.valueOf(listEntry));
    }
    return values;

} else if ...
} else if ...
} else if ...

(please keep in mind that this example is pseudo code)

So of course i'm trying to get rid of the duplicate code. But how? Is it possible to:

1. Get a class from a string? ("SomeEnumClass" -> SomeEnumClass.class)
2. Then check if that class is castable to Enum or something?
3. Access the enum's valueOf() method from that cast?

question from:https://stackoverflow.com/questions/65952514/how-to-access-an-unknown-enums-valueof-method

Answer 1

You can create a Map<String, Class<?>> which contains the mapping like this:

private static final Map<String, Class<Enum<?>>> MAP;
static {
    Map<String, Class<Enum<?>>> map = new HashMap<>();
    map.put(SomeEnumClass.class.getSimpleName(), SomeEnumClass.class);
    // your other enum classes

    MAP = Collections.unmodifiableMap(map);
}

And then you can make use of Enum.valueOf(Class<Enum>, String):

Class<Enum<?>> enumClass = MAP.get(enumNameString);
if (enumClass != null) {
    Collection<Enum<?>> values = new ArrayList<>;
    for (String listEntry : yamlConfig.getStringList(enumNameString)) {
        values.add(Enum.valueOf(enumClass, listEntry));
    }
    return values;
}