Solved help using IntelliJ

If you aren't using maven you can add this as library

FIle -> Project Structure -> Libraries, click in New Project Library (The plus at top left) then select java and searchs the Hikari jar.

 

If you are using Maven all you have to do is add this dependency (and not download anything manually):

HTML:

<dependency>
    <groupId>com.zaxxer</groupId>
    <artifactId>HikariCP</artifactId>
    <version>2.4.5</version>
    <scope>compile</scope>
</dependency>

Edit: Sniped. Btw here's a link on how to add Maven to an existing project if you are interested.

 

Maven will make everything so much easier; as said before - use it!

 

Might as well start now, it will only take 5 minutes to add and will save you alot of time. If you are really insistent on not using Maven, yeah, that method will work.