The new 1.6 TExtAttribute TRACKING doesn't appear to play nice with
LineBreakMeasurer
least on the version of Java I'm using:

Image (tracking.png) attached.
Test case below :

import java.awt.font.*;
import java.awt.*;
import java.awt.geom.*;
import java.text.*;
import java.io.*;
import java.util.*;
import javax.swing.*;

public class TrackingTest {
    private final static String text = "Nunc ut ane vel nis amet.";
    private final static Float fontSize = 62.0f;
    private final static int style = 0;
    private static final float desiredWidth = 284.0f;
    private static final FontRenderContext frc = new FontRenderContext(null, false, false);

    public static void main(String[] args) throws FontFormatException, IOException {
Font font = new Font("serif", style, fontSize.intValue());
JFrame jf = new JFrame("font tracking test");
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jf.add(new FontTestPanel(font));
jf.pack();
jf.setSize(300, 300);
jf.setVisible(true);
    }

    static class FontTestPanel extends JPanel {
private final Font font;

FontTestPanel(Font font) {
this.font = font;
}

public void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D)g;
Point2D.Float pt = new Point2D.Float(10, 30);

g2d.setColor(Color.BLUE);
g2d.drawLine((int)pt.x, 0, (int)pt.x, getHeight());
g2d.drawLine((int)(pt.x + desiredWidth), 0, (int)(pt.x + desiredWidth), getHeight());

renderText(g2d, null, pt);
renderText(g2d ,0f, pt);
renderText(g2d, -.02f, pt);
renderText(g2d, 0.1f, pt);
}

private void renderText(Graphics2D g2d, Float tracking, Point2D.Float loc) {
AttributedString attributedString = new AttributedString(text);
Font usedFont = font;
if (tracking != null) {
Map m = new HashMap();
m.put(TextAttribute.TRACKING, tracking);
usedFont = font.deriveFont(m);
}
attributedString.addAttribute(TextAttribute.FONT, usedFont);
LineBreakMeasurer lineMeasurer = new LineBreakMeasurer(attributedString.getIterator(), frc);
TextLayout layout;
while (null != (layout = lineMeasurer.nextLayout(desiredWidth))) {
loc.y += layout.getAscent();
g2d.setColor(Color.RED);
g2d.drawLine((int)loc.x, (int)loc.y, (int)layout.getAdvance(), (int)loc.y);
g2d.setColor(Color.BLACK);
layout.draw(g2d, loc.x, loc.y);
loc.y += layout.getDescent() + layout.getLeading();
}
loc.y += 20;
}
    }
}