According to 2020 RoamMap update in ICON,

https://medium.com/helloiconworld/2020-roadmap-update-2e12f7bbdcc4

One of the main themes is BTP/sidechain. In this roadmap, JVM is introduced. So developer write SCORE code in java language.

IntelliJ-ICON is a plugin for JetBrains IntelliJ IDEA (an integrated development environment) which helps you write better code in the SCORE.