JDK1.8_stream流

stream流中间操作&filter

 ArrayList<String> list = new ArrayList<>();
        list.add("rfdgfdsf");
        list.add("efdggfddfgsf");
        list.add("wfdgfdgfdgsf");
        list.add("afdgfdgsf");
        list.add("dfdsf");
        list.add("fdsgfdgf");
        list.add("tfdsf");
        list.add("fdsf");
        list.stream().filter(s->s.startsWith("f")).filter(s->s.length()==4).forEach(System.out::println);

stream流中间操作&limit&skip

limit:截取前指定参数的个数
skip:跳过指定参数个数的数据,返回该流剩余元素组成的数据

        ArrayList<String> list = new ArrayList<>();
        list.add("rfdgfdsf");
        list.add("efdggfddfgsf");
        list.add("wfdgfdgfdgsf");
        list.add("afdgfdgsf");
        list.add("dfdsf");
        list.add("fdsgfdgf");
        list.add("tfdsf");
        list.add("fdsf");
        list.stream().skip(2).limit(2).forEach(System.out::println);

stream流中间操作&concat&distinct

concat:合并两个流成为一个新的流
distinct:去掉流中重复的元素

        Stream<String> stringStream1 = list.stream().skip(2);
        Stream<String> stringStream2 = list.stream().limit(2);
        Stream<String> stringStream3 = Stream.concat(stringStream1, stringStream2);
        stringStream3.distinct().forEach(System.out::println);

stream流中间操作&sort

sort:按自然顺序进行排序

       ArrayList<String> list = new ArrayList<>();
        list.add("rfdgfdsf");
        list.add("efdggfddfgsf");
        list.add("wfdgfdgfdgsf");
        list.add("afdgfdgsf");
        list.add("dfdsf");
        list.add("fdsgfdgf");
        list.add("tfdsf");
        list.add("fdsf");
        list.stream().sorted((s1, s2) -> {
    
    
            int num = s1.length() - s2.length();//对首字母和字符串长度进行排序
            int num2 = num == 0 ? s1.compareTo(s2) : num;
            return num2;
        }).forEach(System.out::println);

stream流中间操作&map&sum

        ArrayList<String> list = new ArrayList<>();
        list.add("6546");
        list.add("6546");
        list.add("435435");
        list.add("6546");
        list.stream().map(Integer::parseInt).forEach(System.out::println);
        int sum = list.stream().mapToInt(Integer::parseInt).sum();
        System.out.println(sum);

stream流的收集方式

  public static void main(String[] args) {
    
    
        ArrayList<Integer> list1 = new ArrayList<>();
        list1.add(33);
        list1.add(44);
        list1.add(55);
        list1.add(44);
        //得到数字大于22的流并转成set集合打印输出
        list1.stream().filter(s -> s>22).collect(Collectors.toSet()).forEach(System.out::println);
        String[] list2={
    
    "科比,41","杜兰特,30","詹姆斯,35"};
        //得到字符串中数据大于28的流
        Stream<String> stringStream = Stream.of(list2).filter(s -> Integer.parseInt(s.split(",")[1]) > 28);
        //把获取的流收集到map集合中,key做建,value做值
        Map<String, Integer> map = stringStream.collect(Collectors.toMap(s -> s.split(",")[0], s -> Integer.parseInt(s.split(",")[1])));
        Set<String> keySet = map.keySet();
        for (String key : keySet) {
    
    
            Integer value = map.get(key);
            System.out.println(key+","+value);
        }
    }

stream流的创建方式

        HashMap<Object, Object> map = new HashMap<>();
        Stream<Object> keyStream = map.keySet().stream();
        Stream<Object> valueStream = map.values().stream();
        Stream<Map.Entry<Object, Object>> entryStream = map.entrySet().stream();
        Stream<Integer> integerStream = Stream.of(1, 2, 3);
        Stream<String> stringStream = Stream.of("dd", "dsd", "fdsf");