Java Day9 Stream流

1、认识

2、Stream流使用步骤

3、如何获取Stream流

        //list获取stream流
        List<String> list=new ArrayList<>();
        Collections.addAll(list,"崔十一","张天年","张家","张天爱");
        //需求：将姓张的且名字是三个字的存到一个新的集合中去
        List<String> l = list.stream().filter(s -> s.startsWith("张") && s.length() == 3).collect(Collectors.toList());
        System.out.println(l);//[张天年, 张天爱]
        //set获取stream流
        Set<String> set=new HashSet<>();
        Collections.addAll(list,"崔十一","张天年","张家","张天爱");
        //需求：将姓张的且名字是三个字的存到一个新的集合中去
        Set<String> l1 = list.stream().filter(s -> s.startsWith("张") && s.length() == 3).collect(Collectors.toSet());
        System.out.println(l1);//[张天年, 张天爱]

        //Map获取

        Map<String,Integer> map=new HashMap<>();
        map.put("java",100);
        map.put("java1",200);
        map.put("java2",300);
          //获取键的stream
        map.keySet().stream().filter(s->s.contains("1")).forEach(s -> System.out.println(s));
          //获取值的stream
        map.values().stream().filter(s->s>=200).forEach(System.out::println);
          //获取键值对的stream
        Set<Map.Entry<String, Integer>> entries = map.entrySet();
        entries.stream().forEach(kvs-> System.out.println(kvs.getKey()+"-->"+kvs.getValue()));
        //数组获取STRAMliu
        int[] a=new int[]{1,2,3};
        Arrays.stream(a).filter(s->s>=2).forEach(System.out::println);
        Stream.of(a).forEach(System.out::println);

4.Stream流的中间方法

5、 Stream流终结方法