By the way a month back I read a medium post by a guy who was advocating on why people should not be using kotlin . As of now I must say of the features of java 8 are out of the box supported in android api levels up to 1 , kotlin is not a mandatory language for android its just first class. It will take like a year or two to be deeply integrated in the core elements of android.
Its just that google has now made kotlin more relevant as a competition to app development on ios with swift. Yes there are similarities between syntaxes of swift and kotlin . Try to get well acquainted with java 8 concepts like stream apis , lambdas try with resources and much more and then try kotlin. One of my colleagues once said that for app development he does not find kotlin relevant and after google announced he has now started learning kotlin.