// Тут начало кода
		final Window window = new Window();

		setMainWindow(window);

// Тут продолжение кода

		Button open2SubWindow = new Button("New Win");
		open2SubWindow.addListener(new Button.ClickListener() {
			
			@Override
			public void buttonClick(ClickEvent event) {
				// TODO Auto-generated method stub
				Window sub2window = new Window("My Sub Window");
				window.addWindow(sub2window);
				sub2window.setModal(true);
			}
		});
		window.addComponent(open2SubWindow);

		// Тут начало кода
		mywindow = new Window(windowcaption);
		mywindow.center();
		mywindow.setWidth("700px");
		mywindow.setHeight("500px");
		//mywindow.setModal(true);
		window.addWindow(mywindow);
		// Тут продолжение кода

		Button openSubWindow = new Button("New Win");
		openSubWindow.addListener(new Button.ClickListener() {
			
			@Override
			public void buttonClick(ClickEvent event) {
				// TODO Auto-generated method stub
				Window subwindow = new Window("My Sub Window");
				mywindow.addWindow(subwindow);
				subwindow.setModal(true);
			}
		});
		mywindow.addComponent(openSubWindow);

The method getInstance() is undefined for the type SpravochnikiIASKApplication

package testSubWindowPortlet;

import com.sun.java.swing.plaf.windows.resources.windows;
import com.vaadin.Application;
import com.vaadin.ui.*;
import com.vaadin.*;
import com.vaadin.data.*;
import com.vaadin.ui.CustomComponent;
import com.vaadin.annotations.*;
import com.vaadin.data.Container.Filter;
import com.vaadin.data.Item;
import com.vaadin.data.Property;
import com.vaadin.data.Property.ValueChangeEvent;
import com.vaadin.data.*;
import com.vaadin.data.util.IndexedContainer;
import com.vaadin.event.FieldEvents.TextChangeEvent;
import com.vaadin.event.FieldEvents.TextChangeListener;
import com.vaadin.ui.AbstractTextField.TextChangeEventMode;
import com.vaadin.ui.Button;
import com.vaadin.ui.Button.ClickEvent;
import com.vaadin.ui.Button.ClickListener;
import com.vaadin.ui.*;
import com.vaadin.service.*;
import com.vaadin.terminal.gwt.server.*;
import com.vaadin.portal.gwt.*;

import java.io.Serializable;

import com.vaadin.data.util.*;

@SuppressWarnings("serial")
public class TestSubWindowPortletApplication extends Application {

	@AutoGenerated
	private AbsoluteLayout mainLayout;
	@AutoGenerated
	private Panel panel_1;
	@AutoGenerated
	private VerticalLayout verticalLayout_1;
	@AutoGenerated
	private TabSheet tabSheet_1;
	@AutoGenerated
	private RichTextArea richTextArea_1;
	@AutoGenerated
	private Table table_1;
	@AutoGenerated
	private MenuBar menuBar_1;

	// Переменная для отладки - внутренний номер партии
	public Integer vnutNomerPart = new Integer(0);
	
	public void init() {
		final Window window = new Window();

		setMainWindow(window);


		window.addComponent(new spravochnikIASKpart("Добавить партию",vnutNomerPart, window));



		
	
	}

}

package testSubWindowPortlet;

import java.util.*;

//import spravochnikiIASK.SpravochnikiIASKApplication.parametClassTransfer;

import com.vaadin.Application;
import com.vaadin.ui.*;
import com.vaadin.data.*;
import com.vaadin.data.util.*;
import com.vaadin.ui.Button.*;
import com.vaadin.ui.Button.ClickListener;
import com.vaadin.ui.Window.*;
import com.vaadin.data.Property;
import com.vaadin.data.Property.ValueChangeEvent;
import java.io.PrintStream;
import java.util.Iterator;
import com.vaadin.service.*;
import com.vaadin.terminal.gwt.server.*;
import com.vaadin.portal.gwt.*;


/** Component contains a button that allows opening a window. */
public class spravochnikIASKpart extends CustomComponent
	implements Window.CloseListener {
	Window mainwindow; // Reference to main window
	Window mywindow; // The window to be opened
	Button openbutton; // Button for opening the window
	Button closebutton; // A button in the window
	Label explanation; // A descriptive text
	String windowcaption; //zagolovok okna
	public Integer vnutNomerPartAdd = new Integer(0); 
	public spravochnikIASKpart(String label, Integer vNumPartAdd, Window main) {
		mainwindow = main;
		windowcaption = label;
		vnutNomerPartAdd = vNumPartAdd;
		final VerticalLayout layout = new VerticalLayout();
		openbutton = new Button(windowcaption, this,"openButtonClick");
		layout.addComponent(openbutton);
		setCompositionRoot(layout);
	}
	/** Handle the clicks for the two buttons. */
	public void openButtonClick(Button.ClickEvent event) {
		/* Create a new window. */
		mywindow = new Window(windowcaption);
		mywindow.center();
		mywindow.setWidth("700px");
		mywindow.setHeight("500px");
		mainwindow.addWindow(mywindow);
		mywindow.addListener(this);
		closebutton = new Button("Close", this, "closeButtonClick");
		//добавляем свои элементы
		addpartsdetails();
		mywindow.addComponent(closebutton);
		openbutton.setEnabled(false);
	}
	/** Handle Close button click and close the window. */
	public void closeButtonClick(Button.ClickEvent event) {
		mainwindow.removeWindow(mywindow);
		openbutton.setEnabled(true);
	}
	/** In case the window is closed otherwise. */
	public void windowClose(CloseEvent e) {
		openbutton.setEnabled(true);
	}
	
	public void addpartsdetails(){
				
		//mywindow.addComponent(new WindowOpener("My sub-window", mywindow));
		Button openSubWindow = new Button("New Win");
		openSubWindow.addListener(new Button.ClickListener() {
			
			@Override
			public void buttonClick(ClickEvent event) {
				// TODO Auto-generated method stub
				Window subwindow = new Window("My Sub Window");
				mywindow.addWindow(subwindow);
				subwindow.setModal(true);
				//spravochnikIASKApplication.getInstance().getMainWindow().addWindow(subwindow);
				
			}
		});
		mywindow.addComponent(openSubWindow);
		
		
		
		
		
	}
	

}

The method getInstance() is undefined for the type TestSubWindowPortletApplication

You can only add windows inside application-level windows