Java SE (Java Platform, Standard Edition)

Run the following code and you'll see what the problem I encountered is. Indeed the line highlighting works well without using setCharacterAttributes(). How can I overcome the problem?

import java.awt.*;
import javax.swing.*;
import javax.swing.text.*;
import javax.swing.event.*;

public class LineHighlighterEditor {
    private static class LineHighlighter
	    extends DefaultHighlighter.DefaultHighlightPainter {
	private JTextComponent textComponent;
	private Highlighter highlighter;
	private Object lastHighlight;
	private Element root;

	public LineHighlighter(JTextComponent textComponent, Color color) {
	    super(color);
	    this.textComponent = textComponent;
	    root = textComponent.getDocument().getDefaultRootElement();
	    highlighter = textComponent.getHighlighter();
	    addHighlight();
	    textComponent.addCaretListener(new CaretListener() {
		public void caretUpdate(CaretEvent e) {
		    removeHighlight();
		    addHighlight();
		}
	    });
	}

	public Shape paintLayer(Graphics g, int o0, int o1, Shape s,
				JTextComponent c, View v) {
	    try {
		Rectangle r = c.modelToView(o0);
		r.x = 0;
		r.width = c.getSize().width;
		g.setColor(getColor());
		g.fillRect(r.x, r.y, r.width, r.height);
		return r;
	    } catch (BadLocationException ex) {
		ex.printStackTrace();
		return null;
	    }
	}

	private void addHighlight() {
	    try {
		int line = root.getElementIndex(textComponent.getCaretPosition());
		int offset = root.getElement(line).getStartOffset();
		lastHighlight = highlighter.addHighlight(offset, offset + 1, this);
	    } catch (BadLocationException ex) {
		ex.printStackTrace();
	    }
	}

	private void removeHighlight() {
	    highlighter.removeHighlight(lastHighlight);
	}
    }

    public static void main(String[] arguments) {
	JFrame pad = new JFrame("Line Highlighter Editor");
	pad.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

	JEditorPane editorPane = new JEditorPane();
	pad.setContentPane(editorPane);

	editorPane.setEditorKit(new StyledEditorKit());
	new LineHighlighter(editorPane, Color.CYAN);
	StyledDocument document = (StyledDocument) editorPane.getDocument();

	editorPane.setText("1234");
	document.setCharacterAttributes(0, 2, SimpleAttributeSet.EMPTY, false);

	pad.setBounds(50, 50, 400, 300);
	pad.setVisible(true);
    }
}