How to map a value back to an enum?

Given an enum where each instance is associated with some value:

public enum SQLState
{
  SUCCESSFUL_COMPLETION("00000"),
  WARNING("01000");

  private final String code;
  SQLState(String code)
  {
    this.code = code;
  }
}

How can I construct a Map for efficient reverse look-ups? I tried the following:

public enum SQLState
{
  SUCCESSFUL_COMPLETION("00000"),
  WARNING("01000");

  private final String code;
  private static final Map<String, SQLState> codeToValue = Maps.newHashMap();
  SQLState(String code)
  {
    this.code = code;
    codeToValue.put(code, this); // problematic line
  }
}

but Java complains: Illegal reference to static field from initializer. That is, the static Map is being initialized after all enum values so you cannot reference it from the constructor. Any ideas?