I have a project that uses google calendar. I built the original code in a separate project that used maven.
This is the maven artifact:
Project -> Properties -> Build Path -> Add External Jars
Project -> Clean
You have this problem because
Google HTTP Client Library for Java
Google OAuth Client Library for Java
You did not face this problem in maven as maven downloaded them for you internally. Maven resolves transitive dependencies ie (dependencies that are required for your jar) internally. You did not see that coming.
You can download both from here :
Have a look at maven's dependency resolution mechanism here
Have a look here to get idea of the required dependencies for your current api to work: