TypeSafe Enums + readResolve + New Types

Question

I have the following code:
public final class Type implements java.io.Serializable {
    public static final Type TYPEA= new Type ("TYPEA");
    public static final Type TYPEB= new Type ("TYPEB");
    public static final Type TYPEC= new Type ("TYPEC");
    public static final Type TYPED= new Type ("TYPED");
    private String type;
    public Type (String type) {
        this.type = type;
    public String toString() {
        return this.type;
    private static int nextOrdinal = 0;
    private final int ordinal = nextOrdinal++;
    private static final Type [] VALUES = { TYPEA, TYPEB, TYPEC, TYPED};
    Object readResolve() throws ObjectStreamException {
         return VALUES[ordinal];
}My problem is that I want the user to be able to add a new type for example lets say TYPEF. how would I go about doing this and also make it work with serialiazable?

Answer 1

you can overcome the and .equals() failing with a very minor amount of code. Basically you need a set of all possible typesafe values.
Additionally you need to implement readResolve to prevent serialization from cloning.
Finally - it's just never a good idea to use == for equality comparison. It should only be used for identity comparison (and even then most of the time you should have equals perform the identity comparison).
    private static final Stooge[] ALL = new Stooge{Moe, Larry, Curly};
    //see java.io.Serializable for details
    protected Object readResolve() throws ObjectStreamException {
        return getTypeFor(this.name);
    //you usually need this for retrieval from persistent storage
    public static Stooge getTypeFor(String name){
      Stooge result = null;
      for(int i = 0; i < ALL.length; i++){
        if(ALL.name.equals(name)){
result = ALL[i];
break;
return result;