FULL PRODUCT VERSION :
java version "1.5.0_06"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_06-b05)
Java HotSpot(TM) Client VM (build 1.5.0_06-b05, mixed mode, sharing)

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

EXTRA RELEVANT SYSTEM CONFIGURATION :
This problem manifests itself on all our computers, ranging from Pentium 4 2.8 GHz machines to Pentium 3 1.0 GHz machines.

A DESCRIPTION OF THE PROBLEM :
Java 1.5 suffers from a severe performance problem when displaying text from Asian languages at font sizes of 20 pt or larger.  To display about 50 lines of Korean text in a JTextArea on my computer takes over 12 seconds.  The problem is limited to Java 1.5 and these font sizes.  The exact same code with a Java 1.4.2 JVM will display the text almost instantly.  Changing the font size from 20 pt to 19 pt will causes Java 1.5 to display the text instantly as well.  Anything larger than 20 pt on Java 1.5 is slow.

I have been able to reproduce this problem with many different text components, including JTextArea, JTextPane, and JEditorPane.  The problem appears regardless of whether HTML or plain text is used.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile and run the example program I have included, which opens a JFrame with a JTextArea inside.  When you press a button, the JTextArea is set to a sample of Korean text.

When you click the "Go" button, time how long it takes for text to appear on the screen.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The text should appear in a reasonable amount of time, probably less than 1 second.
ACTUAL -
In Java 1.5 with a font size of 20 pt, the text took 12.15 seconds on my P4 2.8 GHz computer.
In Java 1.4.2 with a font size of 20 pt, the text took less than one second to appear.
In Java 1.5 with a font size of 19 pt, the text took less than one second to appear.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;


/**
 * A simple test to demonstrate the difference in font speed for Asian fonts
 * between Java 1.4.2 and Java 1.5.  Run the program and click the "Go" button
 * to set the text in the text box to some sample text.  When run with a
 * Java 1.4.2 JVM, this happens almost instantly.  However, with Java 1.5
 * the exact same code takes almost 12 seconds to put the text on the screen.
 */
public class FontTest
{
	// A sample of Korean text.  The problem also manifests itself with other
	// Asian language fonts.
	private static String sampleText = "\uc774\ub984\uc774 " +
			"\uc0ac\uc6a9\uc790 \ubaa9\ub85d\uc5d0 \ub098\ud0c0\ub098\uc9c0 " +
			"\uc54a\ub294 \uac83\uc740 \uc5ec\ub7ec\ubd84\uc758 \uac1c\uc778 " +
			"\uc815\ubcf4\uac00 \ucef4\ud4e8\ud130\uc5d0 \uc785\ub825\ub418\uc9c0 " +
			"\uc54a\uc558\uae30 \ub54c\ubb38\uc77c \uc218 \uc788\uc2b5\ub2c8\ub2e4. " +
			"\uc774\uc804\uc5d0 \uc0ac\uc6a9\ud55c \uc801\uc774 \uc5c6\ub358 " +
			"\ucef4\ud4e8\ud130\ub85c \ud504\ub85c\uadf8\ub7a8\uc744 " +
			"\uc2e4\ud589\ud588\uc744 \ub54c \ud754\ud788 \ub098\ud0c0\ub098\ub294 " +
			"\ubb38\uc81c\uc785\ub2c8\ub2e4. \uc544\ub798 \ubc84\ud2bc\uc744 " +
			"\ud074\ub9ad\ud558\uc5ec \uc911\uc559\uc11c\ubc84\uc640 " +
			"\uc5f0\uacb0\ud55c \ud6c4 \uc0c8\ub85c\uc6b4 \uc0ac\uc6a9\uc790 " +
			"\ubaa9\ub85d\uc744 \ubc1b\uc73c\uc138\uc694. \uc774 \ub54c \ub2e4\uc2dc " +
			"\ub85c\uadf8\uc778\uc744 \ud558\uac8c \ub429\ub2c8\ub2e4.";


	// The font size to use when displaying the text.  One interesting thing about
	// this problem is that with a 19 pt font the text draws almost instantly,
	// just like it did with Java 1.4.2.  However, with a 20 pt font, it takes
	// more than 12 seconds to draw on my computer!
	public static final int FONT_SIZE = 20;


	public static void main(String[] args )
	{
		// Generate a decent amount of text to display.  The longer the string
		// the more pronounced the difference is between Java 1.4.2 and Java 1.5.
		for (int i=1; i<=5; i++)
			sampleText += sampleText;

		// Create and display a simple GUI on the event thread.
		SwingUtilities.invokeLater(new Runnable()	{
			public void run()	{
				Font font = new Font("Arial Unicode MS", Font.PLAIN, FONT_SIZE);

				final JTextArea text = new JTextArea();
				text.setLineWrap(true);
				text.setWrapStyleWord(true);
				text.setFont(font);
				text.setEditable(false);

				JButton go = new JButton("Go");
				go.addActionListener(new ActionListener() {
					public void actionPerformed(ActionEvent e) {
						// Set the text in the JTextArea to the sample text.
						text.setText(sampleText);
					}
				});

				JPanel panel = new JPanel(new BorderLayout());
				panel.add(new JScrollPane(text), BorderLayout.CENTER);
				panel.add(go, BorderLayout.NORTH);

				JFrame frame = new JFrame();
				frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
				frame.setContentPane(panel);
				frame.setSize(800, 600);
				frame.setVisible(true);
			}
		});
	}
}

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

CUSTOMER SUBMITTED WORKAROUND :
I have not found a work around for this problem.

Release Regression From : 
The above release value was the last known release where this 
bug was known to work. Since then there has been a regression.