As others have pointed out, it greatly depends on whether you have already "met" another programming language (C#, C++, ...) or not. Going from C++/C# to Java is incredible easy and you perhaps don't need to study Java a lot, you can jump on Android straight away. (Google's developer pages are excellent start).
However, if you don't know anything, I'd recommend to familiarise with Java first, on your PC. Because learning two things (programming in Java + Android ecosystem) is much harder. Not impossible, just harder.
So as soon as you get your basic loops, ifs, classes working, you can take a look at Android examples (so you can actually read them).