# JDC Tech Tips, Special Edition

JDCTechTips@sun.com
Thu, 10 Sep 1998 04:09:29 GMT

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-WELCOME- to the Java(sm) Developer Connection(sm) Tech Tips. This special
edition covers debugging. The JDC Team-

J D C T E C H T I P S
TIPS, TECHNIQUES, AND SAMPLE CODE
* Ctrl-shift-F1 in Swing Applications
* Using Diagnostic Classes with JDK(tm) 1.2
* Java(sm) University(sm) Education Conference

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T I P S , T E C H N I Q U E S , A N D S A M P L E C O D E

CTRL-SHIFT-F1 IN SWING APPLICATIONS. As a programmer, you may have had the
experience of one of your customers having problems with the GUI of a Swing
application you developed in JDK (tm) 1.1 or later. The application seems
to work fine on your machine, but you need to see what's happening on your
customer's machine. Unfortunately, the customer's computer doesn't have
the ability to do screenshots, and you can't diagnose the problem.

So next time you want to solve this kind of GUI problem, try this tip: ask
your customer to type ctrl-shift-F1.

Typing ctrl-shift-F1 displays the GUI hierarchy shown below. The toString
method is called on each component in the GUI tree. Sometimes a component
will have a paramString(), which is also called for that component's own
special diagnostic string.

InternalDialog[dialog0,1,0,189x63,layout=java.awt.BorderLayout,modeless,title=De
mo]
com.sun.java.swing.JRootPane[,5,25,179x33,layout=com.sun.java.swing.JRootPane$
RootLayout]
com.sun.java.swing.JPanel[null.glassPane,0,0,179x33,hidden,layout=java.awt.F
lowLayout] com.sun.java.swing.JLayeredPane[null.layeredPane,0,0,179x33]
com.sun.java.swing.JPanel[null.contentPane,0,0,179x33,layout=com.sun.java.
swing.JRootPane$1] com.sun.java.swing.JDesktopPane[,0,0,0x0]
com.sun.java.swing.JPanel[,0,0,179x33,layout=java.awt.FlowLayout]
com.sun.java.swing.JComboBox[,5,5,169x23,layout=com.sun.java.swing.pla
f.metal.MetalComboBoxUI$MetalComboBoxLayoutManager]
com.sun.java.swing.plaf.metal.MetalComboBoxButton[,0,0,169x23,layout
=com.sun.java.swing.OverlayLayout]
com.sun.java.swing.CellRendererPane[,0,0,0x0,hidden]
com.sun.java.swing.plaf.basic.BasicComboBoxRenderer$UIResource[,-1
43,-16,0x0,invalid]

How can you decipher this hierarchy? Well, it doesn't matter if you're
using Swing or the base AWT, because all the components inherit from
java.awt.Component. This results in the toString method of
java.awt.Component being called for each component in the hierarchy.

The first field inside the [ ] block is the name of the component. The
name is often blank because super() is called to initialize the component
without a parameter. Next come the x and y coordinates followed by the
width x height pair.

If the component is either invalid, hidden, or disabled, then that case is
noted as the next value in the block. If the component is valid, visible,
and enabled, you don't see this parameter.

As noted earlier, some components have a paramString method for custom
diagnostics. Common paramString outputs you might see are the layout
manager class string if the component is in fact a Container, and the mode
and title values if the component is a Dialog (or JDialog). The beginning
of the example shown above, InternalDialog, has both of these paramStrings.

So, with this information you can see if the components are visible, check
which components are possibly due for a repaint (invalid), and see if
components like JButton can be pressed (enabled).

USING DIAGNOSTIC CLASSES WITH JDK(tm) 1.2. If you've worked with JDK 1.1
releases and earlier, you may know that you can substitute diagnostic or
patched classes for the default JDK classes by adding them to the
-classpath parameter when you run your application.

You can still use this feature in JDK 1.2 with a little reconfiguration.
The parameter you need is the -Xsysclasspath option. And in addition to
your own classes you must specify all the classes that the Java Runtime
needs.

Here are two examples. Both use a patch.jar file that contains classes
used instead of their equivalent JDK versions.

-- On Unix

java -Xsysclasspath:patch.jar:/jdk1.2/jre/lib/rt.jar:. myapp

-- On Win95/NT

java
-Xsysclasspath:patch.jar;h:\jdk1.2\jre\lib\rt.jar;h:\jdk1.2\jre\lib\i18n.jar
;. myapp

JAVA(sm) UNIVERSITY(sm) EDUCATION CONFERENCE. If you're interested in
learning more about Java language programming and application development,
attend the Java(sm) University(sm) Education Conference, presented by Sun
Microsystems(tm). The Developers Program includes three curriculum tracks:
Advanced Java Technology, the Java Programming Language for Structured
Developers, and the Fast Track Java Programming Language Certification
program. Also part of the conference is the Java University Lab room,
where you can practice with Java technologies, apply what you learn during
the day's sessions, or check your email. Fully configured,
state-of-the-art workstations will be available -- or bring your own laptop
and plug in.

-- Dates, location, and registration

The Java University Education Conference will be held in two locations:
Internet World Fall, October 7 - 9, 1998 at the Jacob Javits Convention
Center, New York and at Comdex Fall, November 14 - 19, 1998, at the Sands
Expo & Convention Center, Las Vegas. For more information or to register,
see:

http://www.sun.com/java-university

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901 San Antonio Road, Palo Alto, California 94303 USA.

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This issue of the JDC Tech Tips was written by Calvin Austin.

JDC Tech Tips, Special Edition
September 9, 1998

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