How to resolve access to class not allowed

Question

I am calling a class from a Jar file.
But, as soon as that class is called, my application crashes and in LogCat I'm getting an Error:

Caused by: java.lang.IllegalAccessException: access to class not allowed

at java.lang.Class.newInstanceImpl(Native Method)

at java.lang.Class.newInstance(Class.java:1319)

at android.app.Instrumentation.newActivity(Instrumentation.java:1053)

at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2099)

What could be the reason?
Can anyone please help me?