Java Nested Functions

NestedFunWithLambda.java

interface NestedFunWithLambda {

    default String spaces(int count) {
	    
        final BiFunction<String, Integer, String> spaces =
                // compiler complains that spaces may not have been initialized
                (s, i) -> (i < 1) ? s : spaces.apply(s + " ", i - 1);

        return spaces.apply("", count);
    }

}

NestedFunWithLocalClass.java

interface NestedFunWithLocalClass {

    default String spaces(int count) {

        final class Spaces {
            String apply(String s, int i) {
                return (i < 1) ? s : this.apply(s + " ", i - 1);
            }
        }

        return new Spaces().apply("", count);
    }

}

WouldBeNice.java

interface WouldBeNice {

    default String spaces(int count) {

        String spaces(String s, int i) {
            return (i < 1) ? s : spaces(s + " ", i - 1);
        }

        return spaces("", count);
    }

}

Why nested functions? Because interfaces do not allow methods other than public visibility.