java - making changes in the lift app in eclipse

Question

I am working with lift webframe work integrated with eclipse. I have downloaded one sample app from github and now I'm trying to add more lines to it. If any error occured in the project, the localhost:8080 showing some errors even after I have fixed them. After making each changes I used to stop and start my server. But the error is still showing:

   Exception occured while processing /
  Message: java.lang.NoClassDefFoundError: Could not initialize class code.lib.DependencyFactory$
code.snippet.HelloWorld.date(HelloWorld.scala:12)
code.snippet.HelloWorld$$anonfun$howdy$1.apply(HelloWorld.scala:15)
   .......
   .......
   .......

I've tried to revert any changes made by me to initial state of example project, but without any luck.

What I can do with this?