checkbox question

[HellRider]

hi all, I would like to ask how to make the following code , so when the button is pressed to display which checkbox are selected, thank you very much .

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.GridLayout;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.Border;

public class ACheckBox {
  public static void main(String args[]) {
    String title = (args.length == 0 ? "CheckBox Sample" : args[0]);
    JFrame frame = new JFrame(title);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JPanel panel = new JPanel(new GridLayout(0, 1));
    Border border = BorderFactory.createTitledBorder("Pizza Toppings");
    panel.setBorder(border);
    JCheckBox check = new JCheckBox("Anchovies");
    panel.add(check);
    check = new JCheckBox("Garlic");
    panel.add(check);
    check = new JCheckBox("Onions");
    panel.add(check);
    check = new JCheckBox("Pepperoni");
    panel.add(check);
    check = new JCheckBox("Spinach");
    panel.add(check);
    JButton button = new JButton("Submit");
    Container contentPane = frame.getContentPane();
    contentPane.add(panel, BorderLayout.CENTER);
    contentPane.add(button, BorderLayout.SOUTH);
    frame.setSize(300, 200);
    frame.setVisible(true);
  }
}

[zweibieren]

You will want an ItemListener.
The tutorial How to use Checkboxes hints at this, but is not clear.
Here is how to do it with an anonymous listener:

    check = new JCheckBox("Spinach");
    panel.add(check);
    check.addItemListener(new ItemListener() {
        public void itemStateChanged(ItemEvent e) {
            if (e.getStateChange() == ItemEvent.DESELECTED) {
                // "Spinach" has been clicked off, process it
            }
            else { 
                // "Spinach" has been clicked ON, process it
            }
        }
    });