11.java

// Exercise 11: Gather the words into a map, accumulating a count of the
// number of occurrences of each word. Don't worry about upper case and
// lower case. Extra challenge: implement two solutions, one that uses
// groupingBy() and the other that uses toMap().

    @Test
    public void wordFrequencies() throws IOException {
//        Map<String, Long> map = reader.lines()
//                .flatMap(s -> Arrays.stream(s.split(REGEXP)))
//                .filter(s -> !s.isEmpty())
//                .collect(Collectors.groupingBy(s->s, Collectors.counting()));
        Map<String, Long> map = reader.lines()
                .flatMap(s -> Arrays.stream(s.split(REGEXP)))
                .filter(s -> !s.isEmpty())
                .collect(Collectors.toMap(s->s, s->1L, Long::sum));

        assertEquals(2L, (long)map.get("tender"));
        assertEquals(6L, (long)map.get("the"));
        assertEquals(1L, (long)map.get("churl"));
        assertEquals(2L, (long)map.get("thine"));
        assertEquals(3L, (long)map.get("world"));
        assertFalse(map.containsKey("lambda"));
    }