Question

I never had to write GUI in java. This time I can also skip it and use args as UI (user interface).
But I wonder if there is a simple way to create a small GUI to let the user select one of the options.
In other words, to implement the askUser() function where user can select from a drop-down menu and press “ok”.
I spend some time learning this topic, but not even sure that I know which type of GUI i need for this task. JFrame? JPanel? Jmenu? Thanks.

Here is an example of the desired function.

package trygui;

public class Main {

    public static void main(String[] args) {
        String[] choices = new String[]{"cats", "dogs"};
        int choice = askUser(choices);
        System.out.println("selected: " + choices[choice]);
    }

    static int askUser(String[] choices) {
        // create pop-up dialog
        return 0;
    }
}

Update: I use Netbeans, if this can make difference.

Answer 1

The simplest option would be to use the JOptionPane API

public class TestOptionPane03 {

    public static void main(String[] args) {
        new TestOptionPane03();
    }

    public TestOptionPane03() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JPanel panel = new JPanel();
                panel.add(new JLabel("Please make a selection:"));
                DefaultComboBoxModel model = new DefaultComboBoxModel();
                model.addElement("Chocolate");
                model.addElement("Strewberry");
                model.addElement("Vanilla");
                JComboBox comboBox = new JComboBox(model);
                panel.add(comboBox);

                int result = JOptionPane.showConfirmDialog(null, panel, "Flavor", JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE);
                switch (result) {
                    case JOptionPane.OK_OPTION:
                        System.out.println("You selected " + comboBox.getSelectedItem());
                        break;
                }

            }
        });
    }
}

You can find out more by having a read through How to Make Dialogs

UPDATED with feedback

public class TestOptionPane03 {

    public static void main(String[] args) {
        String choice = ask("Chocolate", "Strewberry", "Vanilla");
        System.out.println("You choose " + choice);
    }

    public static String ask(final String... values) {

        String result = null;

        if (EventQueue.isDispatchThread()) {

            JPanel panel = new JPanel();
            panel.add(new JLabel("Please make a selection:"));
            DefaultComboBoxModel model = new DefaultComboBoxModel();
            for (String value : values) {
                model.addElement(value);
            }
            JComboBox comboBox = new JComboBox(model);
            panel.add(comboBox);

            int iResult = JOptionPane.showConfirmDialog(null, panel, "Flavor", JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE);
            switch (iResult) {
                case JOptionPane.OK_OPTION:
                    result = (String) comboBox.getSelectedItem();
                    break;
            }

        } else {

            Response response = new Response(values);
            try {
                SwingUtilities.invokeAndWait(response);
                result = response.getResponse();
            } catch (InterruptedException | InvocationTargetException ex) {
                ex.printStackTrace();
            }

        }

        return result;

    }

    public static class Response implements Runnable {

        private String[] values;
        private String response;

        public Response(String... values) {
            this.values = values;
        }

        @Override
        public void run() {
            response = ask(values);
        }

        public String getResponse() {
            return response;
        }
    }
}