import java.util.Arrays;
import java.util.Optional;

public class Acronym {

    public static String generate(String source) {
        String[] words = source.split("\\b");
        for (String word : words) {
            System.out.println(word);
        }
        Optional<String> acronym = Arrays.stream(words)
                .filter(word -> word.matches("^[a-zA-Z]+$"))
                .reduce((String var0, String var1) -> var0 + var1.substring(0, 1).toUpperCase());
        if (!acronym.isPresent()) {
            throw new RuntimeException();
        }
        return acronym.get();
    }

}