import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class combo extends JFrame implements ActionListener {
JComboBox jcb;
public combo()
{
this.setTitle("ComboBox");
this.setLayout(new FlowLayout());
this.setSize(150,100);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
String[] icerik = {"Seçiniz","Deneme","XYZ","ABC"};
jcb = new JComboBox(icerik);
jcb.setPreferredSize(new Dimension(140, 30));
JButton jbtn = new JButton("Göster");
jbtn.setPreferredSize(new Dimension(120, 30));
jbtn.addActionListener(this);
this.add(jcb);
this.add(jbtn);
this.setVisible(true);
}
@Override
public void actionPerformed(ActionEvent arg0) {
if(jcb.getSelectedIndex()>0)
{
//int index = jcb.getSelectedIndex();
//String secilenbilgi = jcb.getItemAt(index)+"";
JOptionPane.showMessageDialog(this, jcb.getSelectedItem());
jcb.setSelectedIndex(0);
}
}
/**
* @param args
*/
public static void main(String[] args) {
new combo();
}
}

import java.awt.*;
import java.awt.event.*;
import java.util.Vector;
import javax.swing.*;
public class combo1 extends JFrame implements ActionListener, ItemListener {
JComboBox jcb;
//Vector<String> v;
JTextField jtf;
public combo1()
{
this.setTitle("ComboBox 2");
this.setLayout(new FlowLayout());
this.setSize(150,150);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
/*v = new Vector<String>();
v.add("Deneme");
v.add("abc");
v.add("xyz");*/
//jcb = new JComboBox(v);
jcb = new JComboBox();
jcb.addItem("Seçiniz");
jcb.setPreferredSize(new Dimension(140, 30));
//jcb.addItemListener(this);
jtf = new JTextField();
jtf.setPreferredSize(new Dimension(140, 30));
JButton jbtn1 = new JButton("Ekle");
jbtn1.setPreferredSize(new Dimension(140, 30));
jbtn1.addActionListener(this);
jbtn1.setActionCommand("ekle");
JButton jbtn2 = new JButton("Sil");
jbtn2.setPreferredSize(new Dimension(140, 30));
jbtn2.addActionListener(this);
jbtn2.setActionCommand("sil");
this.add(jcb);
this.add(jtf);
this.add(jbtn1);
this.add(jbtn2);
this.setVisible(true);
}
@Override
public void actionPerformed(ActionEvent arg0) {
switch(arg0.getActionCommand())
{
case "ekle": ekle(); break;
case "sil": sil(); break;
}
}
@Override
public void itemStateChanged(ItemEvent e) {
// JOptionPane.showMessageDialog(this, jcb.getSelectedItem());
}
public void ekle()
{
if(jtf.getText().length()>0)
{
jcb.addItem(jtf.getText());
jtf.setText("");
}
}
public void sil()
{
int secilen = jcb.getSelectedIndex();
if(secilen>0){
jcb.removeItemAt(secilen);
jcb.setSelectedIndex(0);
}
}
/**
* @param args
*/
public static void main(String[] args) {
new combo1();
}
}