Desafio Owl

TestCounter.java

package test;

import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collectors;

public class TestCounter {

	public static void main(String[] args) {

		String string = "La verdadera ignorancia no es la ausencia de conocimientos… sino el hecho de rehusarse a adquirirlos";
		String toSearch = "owl";
				
		System.out.println(groupByLetter(string, toSearch));

	}

	public static Map<Character, Long> groupByLetter(String string, String toSearch) {

		Map<Character, Long> toRet = string.chars()
				.mapToObj(TestCounter::toChar)
				.filter(c -> toSearch.indexOf(c) >= 0L)
				.collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
		
		toSearch
			.chars()
			.mapToObj(TestCounter::toChar)
			.forEach(e -> toRet.putIfAbsent(e, 0L));

		return toRet;

	}
	
	private static Character toChar(int i) {
		return Character.toChars(i)[0];
	}
}