Focus on Java, since 99% of online examples on the beginner side will be in Java and learning two language on top of Android will be a lot. There is no need to

Focus on Java, since 99% of online examples on the beginner side will be in Java and learning two language on top of Android will be a lot. There is no need to master Java before you begin learning Kotlin, but currently being able to convert between the two is still a requirement for effective development. Kotlin simply makes your life easier as a Java developer.