NoClassDefFound Exception, when using imported jar from libs

Question

I am trying referencing a libs folder in my project.

1.) I created a simple jar with one single dummy class ImportableDummy.java and exported the project as a jar.

Jar Project:

2.) Then I put the jar into the libs folder inside my Project. The lib is then listed under "Private Libraries":

Jar referencing Project:

3.) At least I doublechecked, that the "PrivateLibraries" are marked as "exported"

QUESTION:

Still there is a java.lang.NoClassDefFoundError: com.test.my.ImportableDummy exception, when I run the App. During compileTime the class is perfectly found by the compiler.

What am I missing?

• P.S. A tried to create a separate lib project for the jar too, with the same result.
• P.P.S. I started Eclipse with the -clean argument with no result

Answer 1

The Problem was, that the Jar was build with compiler 1.7

It should be compiler 1.6 instead.