Why am I getting a NoClassDefFoundError in java?

Question

I managed to successfully compile my code, but I'm not able to execute it. How do I fix this? scannerTesting is my package and ScannerTesting.java is my main file.

D:\Java>javac Testing\src\scannerTesting\ScannerTesting.java

D:\Java>java Testing\src\scannerTesting\ScannerTesting Exception in thread "main" java.lang.NoClassDefFoundError: Testing\src\scannerTesting\ScannerTesting <wrong name: scannerTesting/ScannerTesting> . . .

thejavageek.com/2013/07/21/…

Prasad Kharkar
– Prasad Kharkar

2013-12-20 08:31:27 +00:00
Commented Dec 20, 2013 at 8:31 — Prasad Kharkar
– Prasad Kharkar, Commented Dec 20, 2013 at 8:31

Ben Barkay · Accepted Answer · 2013-12-20 08:27:48Z

3

java -cp ./Testing/src scannerTesting.ScannerTesting

When you run java, it looks for matching classes within its classpath. So what these arguments are doing is add your source folder to the classpath using -cp, and specify that the class that should be run is scannerTesting.ScannerTesting.

For more information, check out java cli tool documentation at Oracle

edited Dec 20, 2013 at 8:27

answered Dec 20, 2013 at 8:17

Ben Barkay

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6 Comments

Alan Over a year ago

It worked when i went to root. Can you explain the logic behind that?

Alan Over a year ago

I'm kind of new to executing files from command prompt, so I would like an explanation to how the above works.

Alan Over a year ago

I also have a file which needs to be read. Which directory should that be in? Currently it's in the Testing folder but it isn't working. However it executes fine when I'm using eclipse

Ben Barkay Over a year ago

Where you run the command matters. You should be in the Testing folder when you execute it, then you could specify -cp as just src. This will set the correct classpath and have the working directory as Testing

Alan Over a year ago

Is there a difference between \ and /?

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fightwithbug · Accepted Answer · 2013-12-20 08:27:23Z

scannerTesting is your package name,right?

If so, I suggest you run command "java" under the workspace D:\Java\Testing\src

java scannerTesting.ScannerTest

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