Paragraph properties with RTF

I can't seem to modify paragraph properties when creating RTF in java.
I can change text to bold, italic, etc. But, if I try to set a
paragraph attribute, e.g. line indent, nothing happens. It's not only
when I display the document in a JEditorPane, the .rtf file I save to
disk doesn't have any line indent either.

What am I doing wrong?

import javax.swing.text.Document;
import javax.swing.text.SimpleAttributeSet;
import javax.swing.text.StyleConstants;
import javax.swing.text.MutableAttributeSet;
import javax.swing.text.rtf.RTFEditorKit;
import java.io.FileOutputStream;
import javax.swing.*;
import java.awt.*;

public class RTFTest extends JFrame
{
  private JEditorPane jep;

  public RTFTest()
  {
    setBounds( 50, 50, 500, 500 );
    setLayout( new BorderLayout() );
    add( jep = new JEditorPane(), BorderLayout.CENTER );
    setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
    jep.setEditable( false );
    jep.setContentType( "text/rtf" );
  }

  public void setDocument( Document d )
  {
    jep.setDocument( d );
  }

  public static void main( String args[] ) throws Exception
  {
    RTFEditorKit aKit = new RTFEditorKit();
    RTFTest r2 = new RTFTest();

    Document d = aKit.createDefaultDocument();
    d.insertString( 0, "Hello world\n", SimpleAttributeSet.EMPTY );
    MutableAttributeSet mas = new SimpleAttributeSet();
    StyleConstants.setBold( mas, true );
    d.insertString( d.getLength(), ".... and this in bold\n", mas );
    StyleConstants.setItalic( mas, true );
    StyleConstants.setBold( mas, false );

    // The following line seems to have no effect. Why?

    StyleConstants.setLeftIndent( mas, 150.0F );

    d.insertString( d.getLength(), "\nThis is another paragraph which
should be in italic and should be indented a bit", mas );

    FileOutputStream out = new FileOutputStream( "test.rtf" );
    aKit.write( out, d, 0, d.getLength() );
    out.close();
    r2.setDocument( d );
    r2.setVisible( true );
  }
}