Could Not Find Class, No Class Definition Found

I'm getting Could not find class and No class definition found error in Android Those classes is inside the jar files. I've added the jar files in a separate folder, but it is not

Solution 1:

The JAR isn't in the CLASSPATH. That error means that the class loader can't find it. Don't believe your eyes; believe the class loader.

Solution 2:

@ddffymo is right.

Have you configure the Build Path? If not here is a way to configure it along with library.

1. create lib or libs folder inside your project structure and then add that library file(JAR) inside this folder.
2. Right click on this JAR file, select Build Path -> Add to Build Path.