Contoh Program Java Menggunakan Kelas JComboBox

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// Nama file : DaftarWarna.java
// Menampilkan daftar warna dengan combo box

// Mengimpor kelas
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;

// Deklarasi kelas
public class DaftarWarna extends JFrame implements ItemListener {

   final int JUMLAH_WARNA = 20;
   private int[] r = new int[JUMLAH_WARNA];
   private int[] g = new int[JUMLAH_WARNA];
   private int[] b = new int[JUMLAH_WARNA];
   private String[] rgb = new String[JUMLAH_WARNA];
   private JComboBox comboBox;
   private JLabel label1, label2, label3;
   private JPanel panel1, panel2;

   // Kontruktor tanpa argumen
   public DaftarWarna() {

      for (int x = 0; x < JUMLAH_WARNA; x++) {
         r[x] = (int) (Math.random() * 256);
         g[x] = (int) (Math.random() * 256);
         b[x] = (int) (Math.random() * 256);

         String strRGB = " RGB = [ " + r[x] + ", " + g[x] + ", " + b[x] + " ]";
         rgb[x] = strRGB;
      }

      comboBox = new JComboBox(rgb);
      comboBox.setBackground(Color.WHITE);
      comboBox.setMaximumRowCount(5);   
      comboBox.addItemListener(this);

      Font font = new Font("Arial", Font.BOLD, 12);

      label1 = new JLabel("", JLabel.CENTER);
      label1.setFont(font);
      label2 = new JLabel("", JLabel.CENTER);
      label2.setFont(font);
      label3 = new JLabel("", JLabel.CENTER);
      label3.setFont(font);

      panel1 = new JPanel();
      panel1.setLayout(new GridLayout(1, 3));
      panel1.add(label1);
      panel1.add(label2);
      panel1.add(label3);

      panel2 = new JPanel();

      // Mengatur warna panel dan teks label pada indek 0
      panel2.setBackground(new Color(r[0], g[0], b[0]));
      label1.setText("RED : " + r[0]);
      label2.setText("GREEN : " + g[0]);
      label3.setText("BLUE : " + b[0]);

      getContentPane().add(comboBox, BorderLayout.PAGE_START);
      getContentPane().add(panel1, BorderLayout.PAGE_END);
      getContentPane().add(panel2, BorderLayout.CENTER);
   }

   // Menangani aksi
   public void itemStateChanged(ItemEvent ie) {
      int indek = comboBox.getSelectedIndex();
      panel2.setBackground(new Color(r[indek], g[indek], b[indek]));
      label1.setText("RED : " + r[indek]);
      label2.setText("GREEN : " + g[indek]);
      label3.setText("BLUE : " + b[indek]);
      repaint();
   }

   // Metoda main
   public static void main(String[] args) {
      DaftarWarna frame = new DaftarWarna();
      frame.setTitle("Kelas DaftarWarna");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setSize(270, 180);
      frame.setVisible(true);
   }
}