code: public void setDefaultAnswer(String variable) {
          if (!isSubmitType()) {
              throw new IllegalStateException("Cannot set an answer if the form is not of type " +
              "\"submit\"");
          }
          FormField field = getField(variable);
          if (field != null) {
              // Clear the old values
              field.resetValues();
              // Set the default value
              for (CharSequence value : field.getValues()) {
                  field.addValue(value);
              }
          }
          else {
              throw new IllegalArgumentException("Couldn't find a field for the specified variable.");
          }
      }
docs: Sets the default value as the value of a given form's field. The field whose variable matches
  the requested variable will be completed with its default value. If no field could be found
  for the specified variable then an exception will be raised.
  
  @param variable the variable to complete with its default value.
  @throws IllegalStateException if the form is not of type "submit".
  @throws IllegalArgumentException if the form does not include the specified variable.