Getting NoClassDefFoundError orgapachelog4jLogger

Hello,

I tried running the same Test_Log4j code which you have in videos with log4j 1.2.17 jar with the same "log4j.properties" file in the video. and got the below error.

"NoClassDefFoundError : org/apache/log4j/Logger"

If i go to the above class, <org/apache/log4j/Logger>, in jar file. i see message "source not found". Can you pls exlpain me what  am i doing wrong here ?

Thanks

Vinay