JTextPaneへのコンポーネント追加時の挙動について

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.text.*;



class JTextPaneTest extends JFrame implements ActionListener{

	JTextPane text;

	JScrollPane scroll;

	JButton button01;

	JButton button02;



	public static void main(String args[]){

		new JTextPaneTest();

	}



	JTextPaneTest(){

		text = new JTextPane();

		scroll = new JScrollPane(text);

		scroll.setPreferredSize(new Dimension(400,300));

		button01 = new JButton("JTextPaneへのコンポーネントの挿入");

		button01.addActionListener(this);

		button01.setActionCommand("ins");

		button02 = new JButton("JTextPaneへの他ドキュメントセット");

		button02.addActionListener(this);

		button02.setActionCommand("set");



		getContentPane().add(scroll,BorderLayout.NORTH);

		getContentPane().add(button01,BorderLayout.CENTER);

		getContentPane().add(button02,BorderLayout.SOUTH);



		pack();

		setTitle("JTextPaneTest");

		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

		text.grabFocus();

		setVisible(true);

	}



	public void actionPerformed(ActionEvent e){

		if(e.getActionCommand().equals("ins")){

			text.insertComponent(new JLabel("ラベルコンポーネント"));

			text.grabFocus();

		}else if(e.getActionCommand().equals("set")){

			text.setDocument(Other.makeStyledDocument("他のクラスで生成されたドキュメント"));

		}

	}

}



class Other{

	public static StyledDocument makeStyledDocument(String ss){

		JTextPane text = new JTextPane();

		text.setText(ss);



		return text.getStyledDocument();

	}

}

class Other {
    public static StyledDocument makeStyledDocument(String ss)
        throws BadLocationException
    {
        StyledDocument document = new DefaultStyledDocument();
        document.insertString(0, ss, null);
        return document;
    }
}