SWT Java Tutorial

The corresponding layout data for the RowLayout class is the RowData class.
RowData can specify the initial width and height of a control.
Layout data objects should not be reused in SWT/JFace

import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.RowData;
import org.eclipse.swt.layout.RowLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.List;
import org.eclipse.swt.widgets.Shell;
public class RowLayoutRowData {
  public static void main(String[] args) {
    Display display = new Display();
    final Shell shell = new Shell(display);
    RowLayout rowLayout = new RowLayout();
    shell.setLayout(rowLayout);
    Button button1 = new Button(shell, SWT.PUSH);
    button1.setText("button1");
    List list = new List(shell, SWT.BORDER);
    list.add("item 1");
    list.add("item 2");
    list.add("item 3");
    list.setLayoutData(new RowData(100, 35));
    
    Button button2 = new Button(shell, SWT.PUSH);
    button2.setText("button #2");
    shell.setSize(450, 200);
    shell.open();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch()) {
        display.sleep();
      }
    }
    display.dispose();
  }
}