I actually have a ton of professional Java experience and have done a lot of microcontroller stuff of late (for fun mainly) and if you go at doing software for ARM Cortex-M microcontrollers the Java way you're going to end with overengineered bloatware.

It's however not a Java-only thing: most of those things have too little memory and processing resources for designing the whole software in a pure OO way, plus you're pretty much coding directly on the low-level (with at most a thin Hardware Abstraction Layer between your code and direct register manipulation) so only ever having used high-level OO languages isn't really good preparation for it, something which applies not only for people with only Java experience but also for those whose entire experience is with things like C#.Net as well as all smartphone frameworks and languages (Objective-C, Kotlin, Swift).