Poor Man's Enum

PoorMansEnum.groovy

import groovy.transform.EqualsAndHashCode

@EqualsAndHashCode
class FooType {
    private static final Map<String, FooType> nameMap = [:]
    private static final Map<String, FooType> identifierMap = [:]
    private static final Set<FooType> values = []

    final String name

    static final FooType A = new FooType('A', 'a')
    static final FooType B = new FooType('B','b')

    protected FooType(String identifier, String name) {
        this.name = name
        if (identifierMap.containsKey(identifier)) {
            throw new IllegalArgumentException("Identifier already taken")
        }
        values << this
        nameMap[name] = this
        identifierMap[identifier] = this

    }

    static Set<FooType> values() {
        Collections.unmodifiableSet(values)
    }

    static FooType valueOf(String identifier) {
        def result = identifierMap[identifier]
        if (result == null) {
            throw new IllegalArgumentException("${this.class.simpleName} type has no constant with the specified identifier.")
        }
        result
    }

    static FooType fromName(String name) {
        nameMap[name]
    }
}

@EqualsAndHashCode
class BarType extends FooType {
    private static final Map<String, BarType> nameMap = [:]
    private static final Map<String, BarType> identifierMap = [:]
    private static final Set<BarType> values = []

    static final BarType C = new BarType('C', 'c')

    protected BarType(String identifier, String name) {
        super(identifier, name)
        values << this
        nameMap[name] = this
        identifierMap[identifier] = this
    }

    static Set<BarType> values() {
        Collections.unmodifiableSet(values)
    }

    static BarType valueOf(String identifier) {
        def result = identifierMap[identifier]
        if (result == null) {
            throw new IllegalArgumentException("${this.class.simpleName} type has no constant with the specified identifier.")
        }
        result
    }

    static BarType fromName(String name) {
        nameMap[name]
    }
}

Map<FooType, Object> asd = [:]
asd[BarType.C] = ''