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Error: java.lang.NullPointerException. Found when running jar file but its fine when running in IDE eclipse, Why?

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I run my code in Eclipse IDE and its fine. I have export it as jar file from Eclipse and run on terminal as jar file, it generates Error: java.lang.NullPointerException. Could not understand why is it so.

posted May 10, 2015 by Sudhakar Singh

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1 Answer

+2 votes

Making a guess -

manifest of the JAR file must contain a line of the form, something like
Main-Class: classname

Here, classname identifies the class having the public static void main(String[] args) method that serves as your application's starting point.

Also look at
http://docs.oracle.com/javase/tutorial/deployment/jar/appman.html

answer May 10, 2015 by Salil Agrawal
Manifest file is fine.
Actually I am running MapReduce code which execute iteratively i.e. multiple times. I exported code as runnable jar form eclipse IDE. And run it as $ hadoop jar filename.jar . I used a public static variable in Mapper class want to use its value in subsequent iterations. NPE causes due to not getting this value in next iteration of job. How to persist a value in multiple classes ? Also I think in Eclipse only a single jvm is running but when running as jar file there will be multiple jvm.
commented May 11, 2015 by Sudhakar Singh
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