Populate JCombobox values depending on another JCombobox

Question

I have two JComboboxes A and B, so if I select any item form A then values related to the item selected in A should fill in JCombobox B. I tried this but get an error:

java.lang.ArrayIndexOutOfBoundsException: 0

at pst.setString(1, client.getSelectedItem().toString());

try
{
    String query="select `User_Name` from Client where `Client_Name`='?' ";
    PreparedStatement pst=conn.prepareStatement(query);
    pst.setString(1, client.getSelectedItem().toString());

    ResultSet rs=pst.executeQuery();

    user.addItem("--Select--");
    while(rs.next())
    {
        user.addItem(rs.getString("User_Name"));            
    }
//      return;
    System.out.println(query);

}
catch(Exception g)
{
    g.printStackTrace();
}

Answer 1

you have done a mistake ,

no need to use '?' , it should be just Client_Name=?

Answer 2

The PresparedStatement takes care of quoting the parameter, when you use setString()

Try

String query="select User_Name from Client where Client_Name = ?";
PreparedStatement pst=conn.prepareStatement(query); 
pst.setString(1, String.valueOf(client.getSelectedItem()));

I guess that when you use '?' the prepared statement does not count this as parameter and this is why you get the IndexOutOfBounce