fizzbuzz.java

rx.Observable.range(1, 100).map(i -> String.valueOf(i).concat(
                (i % 15 == 0 ? "FizzBuzz" : i % 3 == 0 ? "Fizz" : i % 5 == 0 ? "Buzz" : "")))
                .subscribe(System.out::println);


OR, more readable:
  
 rx.Observable.range(1, 100).map(i -> i + suffixFor(i)).subscribe(System.out::println);

...
  
  String suffixFor(int i) {
        return (i % 15 == 0 ? "FizzBuzz" : i % 3 == 0 ? "Fizz" : i % 5 == 0 ? "Buzz" : "");
    }