public Strength nextWeaker()
  {
    switch (strengthValue) {
    case 0: return weakest;
    case 1: return weakDefault;
    case 2: return normal;
    case 3: return strongDefault;
    case 4: return preferred;
    case 5: return strongPreferred;

    case 6:
    default:
      System.err.println("Invalid call to nextStrength()!");
      System.exit(1);
      return null;
    }
  }