Packing the frame solves it.
addAnswerButtonMA.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
answerFieldsMA.add(new JTextField());
checkBoxesMA.add(new JCheckBox());
multipleanswerPanel.add(answerFieldsMA.get(answerFieldsMA.size() - 1));
multipleanswerPanel.add(checkBoxesMA.get(checkBoxesMA.size() - 1));
multipleanswerPanel.revalidate();
validate();
pack()
}
});