URLify in java 8 style functional flavor

 Write a method to replace all spaces in a string with '%20'

Instead of using str.replaceAll("\\s", "%20"), here is a function. This exercise is to help learning.

	public String URLifyJava8(String str) {
	return str.chars()
	.mapToObj(c -> (char) c)
	.flatMap(c -> Character.isWhitespace(c)
	? "%20".chars().mapToObj(ch -> (char) ch) : Stream.of(c))
	.collect(Collector
	.of(StringBuilder::new, StringBuilder::append,
	(r1, r2) -> {
	r1.append(r2);
	return r1;
	},
	StringBuilder::toString, Collector.Characteristics.CONCURRENT));
	}