How to disable certain items in JComboBox

Primarily...

This will require some manual coding. GUI Builder will not help you here.

Regarding rendering ...

You can implement your own BasicComboBoxRendererwhere you pass it ListSelectionModel. Based on the model you are transmitting, only the selected interval will be displayed with a standard renderer. Other indexes will be displayed in the disabled mode, changing the foreground color and its selection background.

^{Note: this will only affect the rendering of items, not the actual selection events.}

import java.awt.Color;
import java.awt.Component;
import javax.swing.JList;
import javax.swing.ListSelectionModel;
import javax.swing.UIManager;
import javax.swing.plaf.basic.BasicComboBoxRenderer;

public class EnabledComboBoxRenderer extends BasicComboBoxRenderer {

    private ListSelectionModel enabledItems;

    private Color disabledColor = Color.lightGray;

    public EnabledComboBoxRenderer() {}

    public EnabledComboBoxRenderer(ListSelectionModel enabled) {
        super();
        this.enabledItems = enabled;
    }

    public void setEnabledItems(ListSelectionModel enabled) {
        this.enabledItems = enabled;
    }

    public void setDisabledColor(Color disabledColor) {
        this.disabledColor = disabledColor;
    }

    @Override
    public Component getListCellRendererComponent(JList list, Object value,
            int index, boolean isSelected, boolean cellHasFocus) {

        Component c = super.getListCellRendererComponent(list, value, index,
                isSelected, cellHasFocus);

        if (!enabledItems.isSelectedIndex(index)) {// not enabled
            if (isSelected) {
                c.setBackground(UIManager.getColor("ComboBox.background"));
            } else {
                c.setBackground(super.getBackground());
            }

            c.setForeground(disabledColor);

        } else {
            c.setBackground(super.getBackground());
            c.setForeground(super.getForeground());
        }
        return c;
    }
}

Regarding the selection of items ...

. , , , . , 1. 2. 3.

private class EnabledListener implements ActionListener {
    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println(((JComboBox) e.getSource()).getSelectedItem());
    }
}

private class DisabledListener implements ActionListener {
    @Override
    public void actionPerformed(ActionEvent e) {
        if (((JComboBox) e.getSource()).getSelectedIndex() != SELECTION_INTERVAL[0]
                && ((JComboBox) e.getSource()).getSelectedIndex() != SELECTION_INTERVAL[1]) {
            JOptionPane.showMessageDialog(null,
                    "You can't Select that Item", "ERROR",
                    JOptionPane.ERROR_MESSAGE);
        } else {
            System.out.println(((JComboBox) e.getSource())
                    .getSelectedItem());
        }
    }
}

protected void enableItemsInComboBox() {
    comboBox.removeActionListener(disabledListener);
    comboBox.addActionListener(enabledListener);
    model.setSelectionInterval(SELECTION_INTERVAL[0], comboBox.getModel()
        .getSize() - 1);
}

protected void disableItemsInComboBox() {
    comboBox.removeActionListener(enabledListener);
    comboBox.addActionListener(disabledListener);
    model.setSelectionInterval(SELECTION_INTERVAL[0], SELECTION_INTERVAL[1]);
}

, EnabledComboBoxRenderer

import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;

import javax.swing.DefaultListSelectionModel;
import javax.swing.JCheckBox;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.SwingUtilities;

public class ComboBoxDisabledItemsDemo {
    private static final int[] SELECTION_INTERVAL = { 0, 1 };

    private JComboBox comboBox;
    private JCheckBox disableCheckBox;
    private DefaultListSelectionModel model = new DefaultListSelectionModel();
    private EnabledComboBoxRenderer enableRenderer = new EnabledComboBoxRenderer();

    private EnabledListener enabledListener = new EnabledListener();
    private DisabledListener disabledListener = new DisabledListener();

    public ComboBoxDisabledItemsDemo() {
        comboBox = createComboBox();

        disableCheckBox = createCheckBox();
        disableCheckBox.setSelected(true); // this adds the action listener to
                                            // the
                                            // to the combo box

        JFrame frame = new JFrame("Disabled Combo Box Items");
        frame.setLayout(new GridBagLayout());
        frame.add(comboBox);
        frame.add(disableCheckBox);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 300);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    private JComboBox createComboBox() {
        String[] list = { "Item 1", "Item 2", "Item 3", "Item 4", "Item 5",
                "Item 6", "Item 7" };
        JComboBox cbox = new JComboBox(list);
        model.addSelectionInterval(SELECTION_INTERVAL[0], SELECTION_INTERVAL[1]);
        enableRenderer.setEnabledItems(model);
        cbox.setRenderer(enableRenderer);
        return cbox;
    }

    private class EnabledListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            System.out.println(((JComboBox) e.getSource()).getSelectedItem());
        }
    }

    private class DisabledListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (((JComboBox) e.getSource()).getSelectedIndex() != SELECTION_INTERVAL[0]
                    && ((JComboBox) e.getSource()).getSelectedIndex() != SELECTION_INTERVAL[1]) {
                JOptionPane.showMessageDialog(null,
                        "You can't Select that Item", "ERROR",
                        JOptionPane.ERROR_MESSAGE);
            } else {
                System.out.println(((JComboBox) e.getSource())
                        .getSelectedItem());
            }
        }
    }

    protected void disableItemsInComboBox() {
        comboBox.removeActionListener(enabledListener);
        comboBox.addActionListener(disabledListener);
        model.setSelectionInterval(SELECTION_INTERVAL[0], SELECTION_INTERVAL[1]);
    }

    protected void enableItemsInComboBox() {
        comboBox.removeActionListener(disabledListener);
        comboBox.addActionListener(enabledListener);
        model.setSelectionInterval(SELECTION_INTERVAL[0], comboBox.getModel()
                .getSize() - 1);
    }

    private JCheckBox createCheckBox() {
        JCheckBox checkBox = new JCheckBox("diabled");
        checkBox.addItemListener(new ItemListener() {
            public void itemStateChanged(ItemEvent e) {
                if (e.getStateChange() == ItemEvent.SELECTED) {
                    disableItemsInComboBox();
                } else if (e.getStateChange() == ItemEvent.DESELECTED) {
                    enableItemsInComboBox();
                }
            }
        });
        return checkBox;
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new ComboBoxDisabledItemsDemo();
            }
        });
    }
}