title: need help on reset/clear jcombobox values
body: <p>im using below coding to add values to a jcombobox using another jcombobox and i need to add the values to the jcombobox2 according to the one get selected in the jcombobox1 without appending values so can someone tell me a way to reset or clear the combo-box values when another option selected? 
  below is my coding and i'm new to java and netbeans so if someone can help i'll be grateful :)</p>
  
  <pre><code>    Class.forName("com.mysql.jdbc.Driver").newInstance();
      Connection con = DriverManager.getConnection("jdbc:mysql://localhost/database1", "root", "senura123");
      Statement stat = (Statement) con.createStatement();
      String val=jComboBox1.getSelectedItem().toString();
      String check; String col;
      if ("Vehicles".equals(val)){
          check = "select reg_no from vehicle;";
          col="reg_no";
      }
      else if ("Travel Guides".equals(val)){
          check = "select username from travelguide;";
          col="username";
      }
      else{
          check = "select username from transportofficer";
          col="username";
      }                   
      ResultSet rslt = stat.executeQuery(check);
      while (rslt.next()) {
          jComboBox2.addItem(rslt.getString(col));                               
      }
   }
  </code></pre>