interface StringFunction { String run(String str); } public class Main { public static void main(String[] args) { StringFunction exclaim = (s) -> s + "!"; StringFunction ask = (s) -> s + "?"; printFormatted("Hello", exclaim); printFormatted("Hello", ask); } public static void printFormatted(String str, StringFunction format) { String result = format.run(str); System.out.println(result); } }