Import java.awt.event. *;

XL class frames implement item listener// excuse.

{

Static selection chc = newchoice (); //Create the object of the drop-down box.

}

Public static void main(String args[])

{

frm . set layout(new FlowLayout())； //Create a layout format

frm.setSize(200，200)； //Set the frame size

frm . add(chc)； //Add a drop-down box component to the frame.

chc . additem listener(frm)； //Set chc as a listener

Chc.add ('Shanghai');

Chc.add ('Beijing'); //Add what you need in the drop-down box, such as Shanghai and Beijing.

frm . set visible(true)； //Make the form visible

}

//The next step is to trigger the drop-down box for execution.