线程“主”中的异常java.lang.IllegalArgumentException：setSelectedIndex：4超出范围

Question

I am trying to make a game, but my code simply does not work and I have no idea why. I am a novice programmer with little experience, and have become very frustrated with my code. I have been trying to fix this problem, but to no avail. Please assist me.

public class hello {
    //Int's and things
    static JButton Play = new JButton("<PLAY>");
    static JFrame pane = new JFrame("CIrCUT 0.0.2");
    static JLabel Title = new JLabel("CIrCUT");
    static JLabel none = new JLabel(" ");
    static JPanel panel = new JPanel(new GridLayout(10, 10, 10, 10));
    static JButton Options = new JButton("<OPTIONS>");
    static JPanel panel2 = new JPanel(new GridLayout(10, 10, 10, 10));
    static String b[] = new String[3];
    static int panelLoct = 1;
    JComboBox optionlist = new JComboBox();

    void initialize() {
        b[0] = "High";
        b[1] = "Medium";
        b[2] = "Low";

        //title
        pane.setTitle("CIrCUT 0.0.2");
        //drop down
        optionlist .setModel(new DefaultComboBoxModel(new String[] {"Option", "High", "Medium",  "Low"}));
        optionlist.setSelectedIndex(4);
        optionlist.addActionListener((ActionListener) this);
        //other pane-related things
        if (panelLoct == 1) {
            pane.setLayout(new GridLayout(10, 10));
            panel.setMaximumSize(new Dimension(500, 500));
            pane.setSize(500, 500);
            pane.setMaximumSize(new Dimension(500, 500));
            panel.add(Title);
            panel.add(none);
            panel.add(Play);
            panel.add(Options);
            panel2.add(optionlist);
            Play.setSize(new Dimension(500, 450));
            pane.setLocation(500, 50);
            pane.setBackground(Color.lightGray);
            pane.setContentPane(panel);
            pane.pack();
            pane.setMinimumSize(new Dimension(500, 500));
            pane.setContentPane(panel);
            OptionButtonHandler cbHandler = new OptionButtonHandler();
            Options.addActionListener(cbHandler);
            pane.setVisible(true);
        }
    }

    public void windowClosing(WindowEvent e) {
        System.exit(0);
    }

    private static class OptionButtonHandler implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            pane.remove(panel);
            pane.add(panel2);
        }
    }

    public void actionPerformed(ActionEvent e) {
        JComboBox cb = (JComboBox) e.getSource();
        cb.getSelectedItem();
    }

    public static void main(String args[]) {
        hello a = new hello();
        a.initialize();
    }
}

I'm thinking that the problem is the JComboBox, but whenever i remove it, i just get an error.

EDIT

here is the error

at javax.swing.JComboBox.setSelectedIndex(Unknown Source)
at hello.initialize(hello.java:36)
at hello.main(hello.java:81)

Answer 1

JComboBox optionlist = new JComboBox();
optionlist.setSelectedIndex(4);

This will cause an exception since you're setting the index of an empty JComboBox. Simply don't do this. Fill the combo box with items before selecting an index.

In fact, where do you add any items to the JComboBox?

Note that in the future if you have a question about an exception that your code generates, you'll want to post the actual exception stacktrace here as well as indicate for us which line throws the exception.

Answer 2

You are setting the model of ComboBox that is having only 4 elements, so the maximum allowed index will be 3(as its 0,1,2,3). So if you are trying to set the selected index to 4th element you must set it 3 as follows :

optionlist .setModel(new DefaultComboBoxModel(new String[] {"Option", "High", "Medium",  "Low"}));
    optionlist.setSelectedIndex(3);

Answer 3

First add some option in optionlist then do this optionlist.setSelectedIndex(4);

 JComboBox optionlist = new JComboBox();
 optionlist .setModel(new DefaultComboBoxModel(new String[] {"Option", "Baby Ride Frame   s/s", "Baby Ring",  "Baby Tri Cycle Frame", "Baby Tri Cycle Frame D/Seat"}));
 optionlist.setSelectedIndex(4);

Answer 4

I was having the exact same problem with eclipse. The error was "setSelctedIndex(0) out of bounds. I solved it by making sure all servers were running on eclipse. That includes mysql, apache and the tomcat server to test for webpages. If you are using eclipse then make sure all local server are on.

Answer 5

That is Because your are trying to show that item which is not Available into the Array list. so make sure that what ever you are trying to show that is Available into the Array list remember that Arraylist is Starting from

JComboBox optionlist = new JComboBox();
optionlist.setSelectedIndex(4);

and you dont have 4th index. Even your combobox is empty so there is not available 4th one. and or do this.

JComboBox optionlist = new JComboBox();
optionlist.setSelectedIndex(-1);