Java Swing - 如何存储键值对

import java.awt.Component;

import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.plaf.basic.BasicComboBoxRenderer;

public class Main {

  public Main() {
    JComboBox comboBox = new JComboBox();
    comboBox.addItem(new Item(1, "-"));
    comboBox.addItem(new Item(2, "X"));
    comboBox.addItem(new Item(3, "Y"));
    comboBox.setMaximumRowCount(3);
    comboBox.setPrototypeDisplayValue(" None of the above ");
    comboBox.addActionListener(e -> {
      JComboBox c = (JComboBox) e.getSource();
      Item item = (Item) c.getSelectedItem();
      System.out.println(item.getId() + " : " + item.getDescription());
    });
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.add(comboBox);
    frame.pack();
    frame.setVisible(true);
  }
  public static void main(String[] args) {
    new Main();
  }
}
class ItemRenderer extends BasicComboBoxRenderer {
  @Override
  public Component getListCellRendererComponent(JList list, Object value,
      int index, boolean isSelected, boolean cellHasFocus) {
    super.getListCellRendererComponent(list, value, index, isSelected,
        cellHasFocus);
    if (value != null) {
      Item item = (Item) value;
      setText(item.getDescription().toUpperCase());
    }
    if (index == -1) {
      Item item = (Item) value;
      setText("" + item.getId());
    }
    return this;
  }
}
class Item {

  private int id;
  private String description;

  public Item(int id, String description) {
    this.id = id;
    this.description = description;
  }

  public int getId() {
    return id;
  }

  public String getDescription() {
    return description;
  }

  @Override
  public String toString() {
    return description;
  }
}