java - Adding an external jar to Order and Export build path generates error in project

Question

I have an eclipse plugin which has it's Java code structured in multiple projects. In one of the projects I added an external jar and used some classes from it. At compilation time no errors where reported, but at runtime, a NoClassDefFoundError exception was thrown. I fixed the problem following this solution.

After this I run a Project -> Clean.. and out of a sudden in a different project I have an error that The method filter(Predicate<? super String[]>) in the type FluentIterable<String[]> is not applicable for the arguments ....

I compared the FluentIterable clasess in both situations and their origin does not modify.

Why is this happening?

Answer 1

I was getting the error because the imported jar was using a different FluentIterable class from a guava jar. I thought the class origin is the same because when I switched back the build path, I did not execute a Project->Clean and eclipse was still pointing to the bad class location.