Eclipse Build Path Jar. Select project, then properties, then java build path, then. Create a new path called lib in your project folder.

Source folders are the root of packages containing.java files. I would make sure that 1) the jar file has.
Select All The Jars In The Lib Folder.
Build path > add to build path;
Expand The Lib Folder In Eclipse.
So what i do is right click on the second project:
Automatically Add Jar From Plugin To Eclipse Project Build Path.
Images References :
Source Folders Are The Root Of Packages Containing.java Files.
These files can contain libraries, frameworks, or utility classes that are.
Setting The Java Build Path.
Select all the jars in the lib folder.
In The Properties Dialog, Select The Java Build Path.