Using a drop down combobox in SWT

Main.java:

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Combo;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Group;
import org.eclipse.swt.widgets.Shell;
 
public class Main {
   public static void main(String[] args) {
      Display display = new Display();
      Shell shell = new Shell(display);
 
      // pos x, pos y, width, height
      shell.setBounds(200, 200, 300, 200);
      shell.setText("SWT Combobox Demonstration");
      shell.setLayout(new GridLayout());
 
      String[] comboData = { "one", "two", "three", "four", "five",
                             "six", "seven", "eight", "nine", "ten",
                             "eleven", "twelve", "thirtheen", "fourteen",
                             "fifteen", "sixteen", "seventeen", "eighteen",
                             "nineteen", "twinty" };
 
      Group comboGroup = new Group(shell, SWT.NULL);
      GridLayout gridLayout = new GridLayout();
      gridLayout.numColumns = 1;
      comboGroup.setLayout(gridLayout);
      comboGroup.setLayoutData(new GridData(GridData.FILL_HORIZONTAL));
      comboGroup.setText("Editable Combo");
       
      Combo combo = new Combo(comboGroup, SWT.DROP_DOWN);
      SelectionListener selectionListener = new SelectionAdapter () {
         public void widgetSelected(SelectionEvent event) {
            Combo combo = ((Combo) event.widget);
            System.out.print(combo.getText());
            System.out.println(" selected = " + combo.getSelection());
         };
      };
      combo.addSelectionListener(selectionListener);
      combo.setItems(comboData);
       
      shell.open();
 
      while (!shell.isDisposed()) {
         if (!display.readAndDispatch()) {
            display.sleep();
         }
      }
      display.dispose();
   }
}