Here is an example of Editable JCombobox.

import java.sql.*;
import java.awt.*;
import java.util.*;
import javax.swing.*;
import java.awt.event.*;
class  EditableComboBox{

    public static void main(String[] args) throws Exception{
        JFrame f=new JFrame();
        f.setLayout(null);
        JLabel lab=new JLabel("Select");
        final JComboBox combo=new JComboBox();
        combo.addItem("Nano");
        combo.addItem("Alto");
        combo.addItem("Swift");
        combo.addItem("WagonR");
        combo.addItem("Scorpio");

        ActionListener actionListener = new ActionListener() {
      public void actionPerformed(ActionEvent actionEvent) {
        ItemSelectable is = (ItemSelectable)actionEvent.getSource();
        String name=selectedString(is);
        System.out.println("Selected: " + name);
        }
    };
       combo.addActionListener(actionListener);
       combo.setEditable(true);
        lab.setBounds(20,20,100,20);
        combo.setBounds(120,20,80,20);
        f.add(lab);
        f.add(combo);

        f.setVisible(true);
        f.setSize(300,120);
    }
    static private String selectedString(ItemSelectable is) {
    Object selected[] = is.getSelectedObjects();
    return ((selected.length == 0) ? "null" : (String)selected[0]);
  } 
}

For more information, visit the following link:

http://www.roseindia.net/java/example/java/swing/AddRemoveItemFromCombo.shtml