import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;

public class Main {

    public static void main(String[] args) throws IOException {
        System.out.println(Files.probeContentType(Paths.get("b.png"))); // Passes
        System.out.println(Files.probeContentType(Paths.get("a#b.png"))); // Fails
    }
}