How to debug a null pointer exception

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Hello,

I got the following error message while trying to make a hangman app . Please help me out here.

Running in the identified_third_party security domain
java.lang.NullPointerException
	at hangman_game.hangman_game.gamevariables(+14)
	at hangman_game.hangman_game.process(+4)
	at hangman_game.hangman_game.commandAction(+12)
	at javax.microedition.lcdui.Display$DisplayAccessor.commandAction(+282)
	at javax.microedition.lcdui.Display$DisplayManagerImpl.commandAction(+10)
	at com.sun.midp.lcdui.DefaultEventHandler.commandEvent(+68)
	at com.sun.midp.lcdui.AutomatedEventHandler.commandEvent(+47)
	at com.sun.midp.lcdui.DefaultEventHandler$QueuedEventHandler.handleVmEvent(+186)
	at com.sun.midp.lcdui.DefaultEventHandler$QueuedEventHandler.run(+57)

Posted 17-Sep-11 20:13pm

psmith33

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Mehdi Gholam · Answer 1 · 2011-09-17T20:52:00

Solution 1

You get a null pointer exception when you are trying to use a variable/object when it has not been assigned/initialized.

From your exception the problem is in the gamevariables method, start by looking there.

Posted 17-Sep-11 20:52pm

Mehdi Gholam

Nagy Vilmos · Answer 2 · 2011-09-29T02:24:00

Run in debug mode and place a breakpoint as it enters the gamevariables method.
Check every object has been initialised before being used.

If this is a regularly called method then it might be better to first run it and allow it to crash, thus letting you identify the line where it throws the exception.

Whatever you do, any decent Java IDE will support easy debugging tasks such as this.