Stream流

构建:

StreamBuilder流构建器，动态 Stream<String> stream = list1.stream();

合并 concat

Stream<Integer> stream1 = Stream.of(1, 2, 3); Stream<Integer> stream2 = Stream.of(4, 5, 6); Stream<Integer> concatenatedStream = Stream.concat(stream1, stream2);

聚合 reduce

Stream<Integer> stream = Stream.of(1, 2, 3, 4, 5); int sum = stream.reduce(0, Integer::sum);

过滤器 filter

List<People> collect = list.stream() .filter(people11 -> people11.getAge() > 22) .collect(Collectors.toList());

Map

取值

List collect = list1.stream().map(people -> people.getAge()).collect(Collectors.toList());

类型转化

List list = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9); List collect = list.stream().map(String::valueOf).collect(Collectors.toList());

flatMap 处理嵌套

List<List<People>> list3 = new ArrayList<>(); list3.stream().flatMap(listPeople -> listPeople.stream()).collect(Collectors.toList()).forEach(System.out::println);

List<List<List<People>>> list4 = new ArrayList<>(); list4.stream().flatMap(lists -> lists.stream().flatMap(listPeople -> listPeople.stream())).collect(Collectors.toList()).forEach(System.out::println);

分组

Map<String, List<People>> collect1 = list.stream() .collect(Collectors.groupingBy(People::getCountry));

并行流

list.stream().parallel() list.parallelStream()