Design Question enums etc

Question

Ok. So I have a class that represents a symbol. A symbol can have many values associated with it e.g name, description, type etc
I have a BaseSymbol which contains a map, which I'm intending to use to store the values associated with a symbol ( as above ) rather than having explicit fields associated with the symbol.
So
BaseSymbol implements ISymbol ( top level interface )
I have a method on ISymbol named getField.
here lies my problem. I originally had getField accept a string as an argument which i then use to access the map to get the appropriate variable. I then have a set of static final strings that represent all possible values for fields within a symbol
e,g usage:
public static final String DESC = "Description"
ISymbol s = new BaseSymbol() - Inside my constructor I set the DESC field to be something like 'This is a symbol'
s.getField(DESC) - returns me ''This is a symbol'
Anyway. I hate the class typing ( using strings ) that go along with this model.
I need a BaseSymbol to have it's map keyed by a safely Typed class rather than a string ( So someone can't pass in an invalid field name )
I started using Enums, but fell short as I want to the extend field options for the future
e.g
Enum SymbolField { CODE, DESC }
Enum ExtraSymbolFields extends SymbolField { EXTRAFIELD1, EXTRAFIELD2 }
Now as you can't do this with Java enums I am interested to hear about any other possible approaches / thoughts?? I was maybe thinking about using a version of the old type safe enum pattern ( which can allow for class extention )?
Your advice is appreciated.

Answer 1

interface Symbol {
  String getSymbol();        
interface ExtraSymbol extends Symbol {
  String getDescription();
enum BasicSymbol implements Symbol {
  DOLLAR("$");
  private final String symbol;
  private BasicSymbol(String symbol) {
    this.symbol = symbol;
  @Override
  public String getSymbol() {
    return symbol;
enum ExtendedSymbol implements ExtraSymbol {
  DOLLAR("$", "US Dollar");
  private final String symbol;
  private final String description;
  private ExtendedSymbol(String symbol, String description) {
      this.symbol = symbol;
      this.description = description;
  @Override
  public String getSymbol() {
      return symbol;
  @Override
  public String getDescription() {
      return description;
}Then you can do:
public <T extends Enum<T> & Symbol> void getSymbol(Class<T> symbolSet) {
    for (Symbol symbol : symbolSet.getEnumConstants()) System.out.println(symbol.getSymbol());
public <T extends Enum<T> & ExtraSymbol> void getSymbolAndDesc(Class<T> symbolSet) {
    for (ExtraSymbol symbol : symbolSet.getEnumConstants()) System.out.println(symbol.getSymbol() + " : " + symbol.getDescription());
}And:
getSymbol(BasicSymbol.class);
getSymbol(ExtendedSymbol.class);
getSymbolAndDesc(ExtendedSymbol.class);