Need Spotify to be running while playing from a client?

[codeNICK]

Understand there is 'Spotify Connect' and allows to switch between playback devices. I'm building a Java client using Spotify Web API and noticed that when I tried to play any tracks, it needs Spotify desktop client to be running and the song plays there instead of the Java client. Also sometimes, I do not get the playback devices. What could be the reason and how do play tracks/albums within the Java client without Spotify desktop app running? 

Plan

Premium

Country

IN

Device

Macbook Pro 2018

Operating System

MacOS

-CodeNiCK