集合之间的相互转换以及与fastjson之间的相互转换

工作中常用到集合之间的相互转换，每次之间的转换都有点问题，需要百度查询，此处做以下简单总结，已便后用；

一：集合之间的互相转换

1.数组 --> List

public static void arrayToList() {
    String[] arr = new String[]{"java", "go", "hadoop", "storm", "Python"};
    //方式1
    List<String> list = new ArrayList<>(Arrays.asList(arr));
    //方式2
    List<String> list2 = List.of(arr);

    list.forEach(v -> log.info(v));
    list2.forEach(v -> log.info(v));
}

2. list --> 数组

public static void ListToArray() {
        List<String> list = new ArrayList<>();
        list.add("java");
        list.add("go");
        list.add("hadoop");
        list.add("storm");
        list.add("Python");
        String[] arr = (String[]) list.toArray();
        for (String v : arr) {
            log.info(v);
        }
 }

3. Map.values --> List

    public static void mapValuesToList() {
        Map<String, String> map = new HashMap(4);
        map.put("java", "01");
        map.put("go", "02");
        map.put("hadoop", "03");
        map.put("storm", "04");
        List<String> list = new ArrayList<>(map.values());
        list.forEach(v -> log.info(v));
    }

4. array --> set

public static void arrayToSet() {
        String[] arr = new String[]{"java", "go", "hadoop"};
        Set<String> set = new HashSet<>(Arrays.asList(arr));
        Iterator<String> stringIterator = set.iterator();
        if (stringIterator.hasNext()) {
            log.info(stringIterator.next());
        }
    }

5.list --> set

   public static void listToSet() {
        List<String> list = new ArrayList<>();
        list.add("java");
        list.add("go");
        list.add("hadoop");
        list.add("storm");
        list.add("Python");
        Set<String> set = new HashSet(list);
        Iterator<String> stringIterator = set.iterator();
        if (stringIterator.hasNext()) {
            log.info(stringIterator.next());
        }
    }

二：fastjson和集合之间的相关转换

　　　1.list --> json 

　　　　1.1 JavaBean

          Person person = JSON.parseObject(jsonString, Person.class);

       1.2 List<JavaBean>

          List<Person> listPerson =JSON.parseArray(jsonString, Person.class);

       1.3 List<String>

          List<String> listString = JSON.parseArray(jsonString, String.class);

       1.4 List<Map<String,Object>>

          List<Map<String, Object>> listMap = JSON.parseObject(jsonString, new TypeReference<List<Map<String,Object>>>(){});