View Full Version : Java: the .class runs, but the .jar does not

April 30th, 2008, 05:41 PM
Okay, I have a tangled JDK because of my AMD-'buntu.

1. Using NetBeans... I create a hierarchy which creates the package.unit line at the start of each source file:


Works fine in NetBeans (and I copied the /images directory over into the build). My program will run from NetBeans IDE.

2. I Clean and Build Final which makes a /dist directory and inside is the .jar file. The .jar will not run. I get:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at fuelcosts.gui.BaseTable.<init>(BaseTable.java:35)
at fuelcosts.gui.PanelEuro.<init>(PanelEuro.java:18)
at fuelcosts.gui.DisplayCards.makeEuro(DisplayCards.j ava:97)
at fuelcosts.gui.DisplayCards.<init>(DisplayCards.java:51)

3. From the Terminal, I can CD into the /build directory, but only to the /classes folder.

java fuelcosts.gui.Frame1 // instead of java Frame1
At first, this technique produced terrible GUI -- lack of Java's fonts. I remembered I installed the IcedTea JDK to get the 64-bit Firefox browser plug-in. Sure enough, the IcedTea jdk/lib has no /fonts. I changed the update-alternatives --config java back to sun-jdk-1.6.4. But I still have no run from.jar capabilities. The Manifest file inside the .jar:

Manifest-Version: 1.0
Ant-Version: Apache Ant 1.7.0
Created-By: 10.0-b19 (Sun Microsystems Inc.)
Main-Class: fuelcosts.gui.Frame1
X-COMMENT: Main-Class will be added automatically by build

Do I need classpath? Do I need to manually configure .jar? It is very tough to make code work and then the final .jar isn't trustworthy. What can I change on my Ubuntu so I get ./ for a classpath?

May 1st, 2008, 02:06 PM
That's the third time this problem occurs in a more or less similar form. Note that in order to read images from a program located in a .jar file, you have to:

Include the images in the .jar file itself - That's the intended to use of the .jar files. They are meant to contain all static data of your application. That's also the reason why ./ isn't in the classpath (on no platform). There's no need to if you use .jar files correctly.
Load your image using Class.getResource()

Note that the exception occurs in your own code, so we can only guess what went wrong. My guess would be that you try to read some data/image and throw away the Exceptions which leads to an NullPointerException later. See also http://ubuntuforums.org/showthread.php?t=669277.

May 2nd, 2008, 11:06 AM
I've done a bit of research since posting this question. NetBeans conception of valid application code -- that isn't monolithic -- means utilizing a Library to wrap classes. Which means I have to resharpen my pencil and go back to the drawing board. For this posted problem I was having, I do have my graphics in the same folder as .class. I have learned a .jar executes much faster than the IDE does. The .jar version considers I/O to the hard drive slow. Putting the call to an ImageObserver or a synchronized thread helps a little bit.

I have been advised on other forums to edit my shell bash, which I hate doing.

this hack almost works...

1. unpack the .jar
2. in the FOLDER called META-INF, edit your manifest.mf file by hand
and put in this folder.
3. add this hacked folder containing the file. It will replace the existing manifest.mf file with your recent one

<jar file="client.jar" update="true">
<attribute name="Class-Path" value="
<attribute name="Main-Class" value="com.sun.Test"/>
<section name="Mapping Info">
<attribute name="Built-By" value="${user.name}"/>