Abstract Enums

Abstract Enums.md

Hello,

I'd like to talk about abstract enums. In Java, you have enums:

public enum MyEnum {
    MY_ENUM_VALUE,
    MY_OTHER_ENUM_VALUE;
}

You can't extend another enum, or make abstract enums, and an enum is defined as being tagged ENUM in bytecode and directly subclassing Enum.

My proposal is to add abstract enums, allowing you to require an enum with specific methods:

public abstract enum MyAbstractEnum {
    // cannot define values
    private final String humanReadableName;
    protected MyAbstractEnum(String humanReadableName) {
        this.humanReadableName = humanReadableName;
    }
    public final String getHumanReadableName() {
        return this.humanReadableName;
    }
}
public enum MyEnum extends MyAbstractEnum {
    MY_ENUM_VALUE("My Enum Value"),
    MY_FANCY_ENUM_VALUE("My Fancy Enum Value");
}

// somewhere else
public class ConfigurationManager<T extends MyAbstractEnum> {
    public ConfigurationManager(Class<? extends T> fields) {
        try {
            T[] values = (T[]) fields.getMethod("values").invoke(null);
            /* parse values */
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
    /* ... */
    public void write(OutputStream stream) {
        /* ... */
        String name = field.getHumanReadableName();
        /* ... */
    }
    /* ... */
}

And then change what's an enum to:

• Has to be marked as ENUM
• Has to be subclass of Enum
• Has to have abstract superclass
• (Hmm how can we make it so values can't be accidentally seen as an enum? Meh, add another mark: ENUM_VALUE (alternatively: has to be abstract. but that'd require extra classes to be made (NOT 1 PER VALUE THO!)))

Then I'd be able to have my enum-based config files.