You don’t need to know Java to learn Kotlin. And frankly, Kotlin is much easier to learn, than Java. Then again, Swift (iOS) is easier to learn than Kotlin, but the two languages are extremely similar. I’m teaching a college course on mobile design and development, and I chose to teach it entirely in Kotlin - ZERO Java. Some of the students have some programming background but others have never programmed before. I did find, however, that pretty much all the books out there on Kotlin assume (a) you already are an Android expert and (b) you are already a Java guru. That’s why I decided to write my own book, not just for my students but for iOS developers who want to learn Android for the first time. They are already well versed in Swift so Kotlin is an easy move for them. And they either never want to touch Java code again or they have never done Java dev and the thought of Java is what has kept them away from Android in the first place.