I’ve just released an MP3 Player that runs in IntelliJ IDEA and other JetBrains IDE’s such as Android Studio or PyCharm.
It can open mp3, ogg, flac audio files, add a playlist change volume and equalizer.
To run it, download the free Applet Runner plugin from JetBrains marketplace and execute the free MP3 Player applet located at https://www.japplis.com/applet-runner/player/jlgui-player.html.