import java.util.stream.Stream;
 
import static java.util.Arrays.stream;
import static java.util.stream.Collectors.joining;
 
public class Main {
    public static String getRoute(String source, String destination, String... layovers) {
        final Stream<String> route = Stream.concat(Stream.of(source), Stream.concat(stream(layovers), Stream.of(destination))) ;
 
        return route.peek(s -> {
            if (s.trim().isEmpty()) throw new IllegalArgumentException();
        }).collect(joining("->"));
    }
 
    public static void main(String[] argv) {
        System.out.println(getRoute("JFK", "DEN","SFO", "LAX"));
    }
}
 

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