MainWindow

import org.eclipse.swt.SWT;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Group;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.events.*;


//Main window
public class MainWindow
{
    Display display;
    Shell shell;
    Text text;
    int radiobuttonsQuantity = 3;
    Button[] radiobuttons;
    Button button;

    //Run the window
    public void run()
    {
        display = new Display();
        shell = new Shell();
        shell.setSize(480, 320);
        shell.setText("Lab 1");
        createContent(shell);
        shell.open();

        //The cycle wich track down windows' destruction
        while (!shell.isDisposed())
        {
            if (!display.readAndDispatch())
            {
                display.sleep();
            }
        }
        display.dispose();
    }

    //Create main window's content
    private void createContent(Shell shell)
    {
        //Vertical FillLayout
        FillLayout fillLayout = new FillLayout();
        fillLayout.type = SWT.VERTICAL;
        fillLayout.marginHeight = fillLayout.marginWidth = fillLayout.spacing = 10;

        //Text input field
        text = new Text(shell, SWT.NULL);
        text.setData("Enter smth: ");

        //Radiobutton grouping
        Group radiobuttonsGroup = new Group(shell, SWT.NONE);
        radiobuttonsGroup.setLayout(new FillLayout(SWT.VERTICAL));
        radiobuttonsGroup.setText("Choices");

        //A procedural generation of radiobuttons
        radiobuttons = new Button[radiobuttonsQuantity];
        for (int currRadiobuttonNumb = 0; currRadiobuttonNumb < radiobuttonsQuantity; currRadiobuttonNumb++)
        {
            radiobuttons[currRadiobuttonNumb] = new Button(radiobuttonsGroup, SWT.RADIO);
            radiobuttons[currRadiobuttonNumb].setSelection(false);
            radiobuttons[currRadiobuttonNumb].setText("RB " + Integer.toString(currRadiobuttonNumb + 1));
        }

        //Button
        button = new Button(shell, SWT.PUSH);
        button.setBounds(40, 50, 50, 20);
        button.setText("Click Me");
        //???
        button.addSelectionListener(new SelectionListener()
        {

            @Override
            public void widgetSelected(SelectionEvent event)
            {
                radiobuttonSelector(text.getText());
            }

            @Override
            public void widgetDefaultSelected(SelectionEvent event)
            {
              text.setText("No problem");
            }
          });

        shell.setLayout(fillLayout);
    }

    //Select inputted radiobutton
    public void radiobuttonSelector(String text)
    {
        boolean isFound = false;
        for (int currRadiobuttonNumb = 0; currRadiobuttonNumb < radiobuttonsQuantity; currRadiobuttonNumb++)
        {
            if (text.equals(radiobuttons[currRadiobuttonNumb].getText()))
            {
                radiobuttons[currRadiobuttonNumb].setSelection(true);
                isFound = true;
            }
        }
        if (!isFound)
        {
            new ErrorWindow(shell).run();
        }
    }

    public static void main(String[] args)
    {
        new MainWindow().run();
    }
}