I wanted to create a FizzBuzz in Java that is supposed to be open for extension.

So the initial problem is the good old, if divisible by 3 print fizz, if divisible by 5 print buzz, if divisible by both print fizzbuzz, otherwise print the number itself.

But I want to be able to change the numbers that we test against (3 and 5 can become 4 and 6) and the words we print (fizz and buzz may be come foo and bar). And there may be new ones added, such as 7, qux..

Here is what I came up with, any suggestions are welcome:

import java.util.*;
import java.util.function.Function;
import java.util.function.IntPredicate;

class App {
    public static void main(String[] args) {
        Function<Integer, IntPredicate> divisibilityPredicateBuilder 
            = isDivisibleBy -> x -> x % isDivisibleBy == 0;

        final Map<Integer, String> fizzersBuzzers = new HashMap<>();
        fizzersBuzzers.put(3, "fizz");
        fizzersBuzzers.put(5, "buzz");

        for (int i = 1; i < 101; i++) {
            String fizzBuzz = "";

            for (Integer fizzerBuzzer : fizzersBuzzers.keySet()) {
                if (divisibilityPredicateBuilder.apply(fizzerBuzzer).test(i)) {
                    fizzBuzz += fizzersBuzzers.get(fizzerBuzzer);
                    fizzBuzz += " ";

            if (fizzBuzz.isEmpty()) {
                fizzBuzz = String.valueOf(i);


1 Answer 1


You used a HashMap, where the iteration order is arbitrary. There is no guarantee whether you'll get "fizz buzz" or "buzz fizz"!

  • \$\begingroup\$ yes very good catch Must use sortedmap \$\endgroup\$ Commented Oct 26, 2018 at 14:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.