private Map<Character, ArgumentMarshaler> stringArgs =
      new HashMap<Character, ArgumentMarshaler>();
...
  private void parseStringSchemaElement(char elementId) {
    stringArgs.put(elementId, new StringArgumentMarshaler());
  }
...
  private void setStringArg(char argChar) throws ArgsException {
    currentArgument++;
    try {
      stringArgs.get(argChar).setString(args[currentArgument]);
    } catch (ArrayIndexOutOfBoundsException e) {
      valid = false;
      errorArgumentId = argChar;
      errorCode = ErrorCode.MISSING_STRING;
      throw new ArgsException();
    }
  }
...
  public String getString(char arg) {
    Args.ArgumentMarshaler am = stringArgs.get(arg);
    return am == null ? "" : am.getString();
  }
...
  private class ArgumentMarshaler {
    private boolean booleanValue = false;
    private String stringValue;

    public void setBoolean(boolean value) {
      booleanValue = value;
    }

    public boolean getBoolean() {
      return booleanValue;
    }

    public void setString(String s) {
      stringValue = s;
    }

    public String getString() {
      return stringValue == null ? "" : stringValue;
    }
  }