FULL PRODUCT VERSION :
java version "1.6.0_23"
Java(TM) SE Runtime Environment (build 1.6.0_23-b05)
Java HotSpot(TM) Client VM (build 19.0-b09, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

EXTRA RELEVANT SYSTEM CONFIGURATION :
Windows XP Japanese
(I do not investigate other national language version.)

A DESCRIPTION OF THE PROBLEM :
When I print a multi-byte character less than 7-point, a real print result is different from FontMetrics.stringWidth().

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Windows XP SP3 Professional (Japanese)
Execute sample code
select "File" -> "Print"

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The length of the underline almost accords with printed character string.
ACTUAL -
The length of the underline does not accord with character string printed by a font size.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package sample;

import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.JobAttributes;
import java.awt.PageAttributes;
import java.awt.PrintJob;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.SwingUtilities;

public class SamplePrint extends JFrame implements ActionListener, Runnable {

    static final int OFFSET_X = 30;
    static final int OFFSET_Y = 30;
    static final int X2 = 50;
    static final int BETWEEN_LINES = 10;

    /**
     * @param args
     */
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new SamplePrint());
    }

    public void run() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JMenuBar mb = new JMenuBar();
        JMenu menu = new JMenu("File");
        JMenuItem item = new JMenuItem("Print");
        item.addActionListener(this);
        menu.add(item);
        mb.add(menu);
        setJMenuBar(mb);
        setSize(150, 150);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        String title = "PrintJob";

        JobAttributes job = new JobAttributes();
        PageAttributes page = new PageAttributes();
        page.setOrientationRequested(3); // portrait
        page.setMedia(PageAttributes.MediaType.A4);

        // show dialog
        PrintJob printJob = Toolkit.getDefaultToolkit().getPrintJob(this,
                title, job, page);

        //
        Graphics g = printJob.getGraphics();

        // java version print
        Font titleFont = new Font("Monospaced", Font.PLAIN, 7);
        g.setFont(titleFont);
        g.drawString("size width " + System.getProperty("java.vm.name")
                + " " + System.getProperty("java.version"), OFFSET_X, OFFSET_Y);

        Font basefont = new Font("Monospaced", Font.PLAIN, 1);
        for (int i = 0; i < 61; i++) {
            String tmp = "\uff11\uff12\uff13\uff14\uff15\uff16\uff17\uff18\uff19\uff10";
            String str = tmp + tmp + tmp + tmp + tmp + tmp + tmp;

            float fontSize = ((float) (i + 10)) / 10;
            Font font = basefont.deriveFont(fontSize);
            g.setFont(font);
            FontMetrics fm = g.getFontMetrics();
            // System.err.println(fm);
            int width = fm.stringWidth(str);
            int y = (i + 1) * BETWEEN_LINES + OFFSET_Y;

            g.drawString(str, OFFSET_X + X2, y);
            g.drawLine(OFFSET_X + X2, y, OFFSET_X + X2 + width, y);

            g.setFont(titleFont);
            g.drawString("" + fontSize + " " + width, OFFSET_X, y);
        }
        printJob.end();
    }
}

---------- END SOURCE ----------