A JAR (Java ARchive) file is a package format used to bundle Java class files, metadata, and resources (like the Quranic text and audio) into a single, compressed file for distribution on mobile devices.
This resolution (320x240) is a common standard for various electronic Quranic devices and older mobile platforms. Digital Quran Speakers & Players
So go ahead. Load that JAR file. Set that wallpaper. Keep the Quran close—even if your screen is only 320 pixels wide and 240 pixels tall.
Some digital "Quran players" or speakers sold on wholesale sites like Alibaba still utilize these lightweight Java-based interfaces for their built-in LCD screens.