How to rad an error?

[arun mahajan]

Hi,
I always wondered how to read the java erorrs printstsck. Can some body helpme for it? Is there any reference sites available.

Exception occurred during event dispatching:
java.lang.NullPointerException
at LogoServer.actionPerformed(LogoServer.java:123)
at javax.swing.AbstractButton.fireActionPerformed(Compiled Code)
at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(Abstra
ctButton.java:1101)
at javax.swing.DefaultButtonModel.fireActionPerformed(Compiled Code)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:250
)
at javax.swing.AbstractButton.doClick(AbstractButton.java:226)
at javax.swing.plaf.basic.BasicMenuItemUI$MouseInputHandler.mouseRelease
d(BasicMenuItemUI.java:674)
at java.awt.Component.processMouseEvent(Compiled Code)
at java.awt.Component.processEvent(Compiled Code)
at java.awt.Container.processEvent(Compiled Code)
at java.awt.Component.dispatchEventImpl(Compiled Code)
at java.awt.Container.dispatchEventImpl(Compiled Code)
at java.awt.Component.dispatchEvent(Compiled Code)
at java.awt.LightweightDispatcher.retargetMouseEvent(Compiled Code)
at java.awt.LightweightDispatcher.processMouseEvent(Compiled Code)
at java.awt.LightweightDispatcher.dispatchEvent(Compiled Code)
at java.awt.Container.dispatchEventImpl(Compiled Code)
at java.awt.Window.dispatchEventImpl(Compiled Code)
at java.awt.Component.dispatchEvent(Compiled Code)
at java.awt.EventQueue.dispatchEvent(Compiled Code)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:68)

regards,
Arun

[Paul Stevens]

You got a NullPointerException in your actionPerformed() of LogoServer class line 123. Generally the first couple of lines gives you the error you should be concerned with. The rest is just a trace of every other method.

java.lang.NullPointerException
at LogoServer.actionPerformed(LogoServer.java:123)

[arun mahajan]

Thanks Paul for you reply.
But I am interested to study this error in detail Line By Line. Is there any body to help?
Arun

[Paul Stevens]

It is a trace of everything that was involved. Each line tells you the class and method. I am not sure what more you are after.

[Matthew Phillips]

I will break down the following line:
at LogoServer.actionPerformed(LogoServer.java:123)

This tells you that the error occured in the class LogoServer at line 123 of the source code.

[arun mahajan]

Thanks to all for their support to this thread. I may sound stupid but would like to dig in it a bit more if you help me.
What I am askign an explanation for lines like:
at javax.swing.AbstractButton.fireActionPerformed(Compiled Code)
What does it says?
what following line says:
at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(Abstra
ctButton.java:1101)
Is above is telling me that error came on the mentioned line ofcompiled code?
And moreover is this stack is telling me how my java code is travelling?
I am sorry if it sound foolish?
Arun

[Paul Stevens]

As I said. Each line tells you the class and method. Yes it is the path that java took to get where it is (stack trace). I really don't know what else I can tell you.
javax.swing.AbstractButton.fireActionPerformed(Compiled Code)
Class AbstractButton
Method fireActionPerformed()