Java by API/javax.swing/ListCellRenderer

implements ListCellRenderer

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.ruponent;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.DefaultListCellRenderer;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.ListCellRenderer;
public class MainClass {
  public static void main(String args[]) throws Exception {
    Color colors[] = { Color.GREEN, Color.ORANGE, Color.PINK, Color.RED,
        Color.WHITE, Color.YELLOW };
    JFrame frame = new JFrame("Color JComboBox");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    final JComboBox comboBox = new JComboBox(colors);
    comboBox.setMaximumRowCount(5);
    comboBox.setEditable(true);
    comboBox.setRenderer(new ColorCellRenderer());
    frame.add(comboBox, BorderLayout.NORTH);
    final JLabel label = new JLabel();
    label.setOpaque(true);
    label.setBackground((Color) comboBox.getSelectedItem());
    frame.add(label, BorderLayout.CENTER);
    ActionListener actionListener = new ActionListener() {
      public void actionPerformed(ActionEvent actionEvent) {
        Color selectedColor = (Color) comboBox.getSelectedItem();
        label.setBackground(selectedColor);
      }
    };
    comboBox.addActionListener(actionListener);
    frame.setSize(300, 200);
    frame.setVisible(true);
  }
}
class ColorCellRenderer implements ListCellRenderer {
  protected DefaultListCellRenderer defaultRenderer = new DefaultListCellRenderer();
  private final static Dimension preferredSize = new Dimension(0, 20);
  public Component getListCellRendererComponent(JList list, Object value, int index,
      boolean isSelected, boolean cellHasFocus) {
    JLabel renderer = (JLabel) defaultRenderer.getListCellRendererComponent(list, value, index,
        isSelected, cellHasFocus);
    if (value instanceof Color) {
      renderer.setBackground((Color) value);
    }
    renderer.setPreferredSize(preferredSize);
    return renderer;
  }
}