分组​​List​​并显示其总数。

@Test
public void test8() {
    //3 apple, 2 banana, others 1
    List<String> items =
            Arrays.asList("apple", "apple", "banana",
                    "apple", "orange", "banana", "papaya");
    Map<String, Long> result =
            items.stream().collect(
                    Collectors.groupingBy(
                            Function.identity(), Collectors.counting()
                    )
            );
    System.out.println(result);

}