public static void main(String[] args) {

   // Collection 体系的集合可以使用默认 stream () 方法生成流

   ArrayList<String> list = new ArrayList<>();

   Stream<String> stream = list.stream();

   Set<String> set = new HashSet<>();

   Stream<String> stream1 = set.stream();

   // Map 体系的集合间接调用 stream () 方法生成流

   Map<String, Integer> map = new HashMap<>();

   Stream<String> stream2 = map.keySet().stream();

   Stream<Integer> stream3 = map.values().stream();

   Stream<Map.Entry<String, Integer>> stream4 = map.entrySet().stream();

   // 数组通过 Arrays 中的静态方法 stream () 生成流

   String strings[] = {"hello","world","java"};

   Stream<String> stream5 = Arrays.stream(strings);

   // 同种数据类型的多个数据可以通过 Stream 接口的静态方法 of (T ... Values) 生成流

   Stream<String> hello = Stream.of("hello", "world", "java");

}