public class web {


    public static void main(String[] args) {
        List<User> users = new ArrayList<>();
        users.add(new User("1",1,"張三","zzz","愿你所有的日子都比不上明天的光輝"));
        users.add(new User("2",2,"李四","xxx","花有重開(kāi)日，人無(wú)再少年"));
        users.add(new User("3",3,"王五","zzz","我想真正的成熟應(yīng)該并不是追求完美，而是直面自己的缺憾，這才是生活的本質(zhì)"));
        users.add(new User("4",4,"趙六","zc","生活不可能像你想的那么好浓冒，但也不會(huì)像你想的那么糟之拨。我覺(jué)得人的脆弱和堅(jiān)強(qiáng)都是超乎自己想象的哼御。有時(shí)骤肛，人可能脆弱得一句話就淚流滿面诱咏。有時(shí)昌粤，也發(fā)現(xiàn)自己咬著牙走了很長(zhǎng)的路"));
        users.add(new User("1",5,null,"zzz","人生當(dāng)中成功只是一時(shí)的既绕，失敗卻是主旋律"));

        List<String> userIds = getUserIds(users);
        System.out.println(userIds);
        List<String> userIds8 = getUserIds8(users);
        System.out.println(userIds8);
        Set<String> userIds2 = getUserIds2(users);
        System.out.println(userIds2);
        List<Long> userIds10 = getUserIds10(userIds);
        System.out.println(userIds10);
        String[] s= {"2","3","1","4","6"};
        List<String> userIds11 = getUserIds11(s);
        System.out.println(userIds11);
        Map<String, User> map = getMap(users);
        System.out.println(map);
        Map<String, List<User>> mapGroup = getMapGroup(users);
        System.out.println(mapGroup);
    }

    /**
     * jdk8 從集合對(duì)象中獲取用戶ID集合
     * @param userList
     * @return
     */
    public static List<String> getUserIds(List<User> userList){
        List<String> userIds = userList.stream().map(User::getUuid).collect(Collectors.toList());
        userList.stream().collect(Collectors.groupingBy(a ->a.getName().equals("張三")));
        return userIds;
    }

    /**
     * jdk8 從集合對(duì)象中篩選出用戶ID不為空的數(shù)據(jù)
     * @param userList
     * @return
     */
    public static List<String> getUserIds8(List<User> userList){
        List<String> userIds = userList.stream().filter(item -> item.getName() != null).map(User::getUuid).collect(Collectors.toList());
        return userIds;
    }

    /**
     * jdk8 從集合對(duì)象中篩選出用戶ID不為空的數(shù)據(jù)，并進(jìn)行去重
     * @param userList
     * @return
     */
    public static Set<String> getUserIds2(List<User> userList){
        Set<String> userIds = userList.stream().filter(item -> item.getName()!= null).map(User::getUuid).collect(Collectors.toSet());
        return userIds;
    }

    /**
     * jdk8 將Long類型數(shù)據(jù)轉(zhuǎn)換成String類型
     * @param userIds
     * @return
     */
    public static List<Long> getUserIds10(List<String> userIds){
        List<Long> userIdStrs = userIds.stream().map(x -> new Long(x)).collect(Collectors.toList());
        return userIdStrs;
    }

    public static List<String> getUserIds11(String[] userIds) {
        //創(chuàng)建一個(gè)字符串?dāng)?shù)組
//        String[] strArray = new String[]{"a","b","c"};
        //轉(zhuǎn)換后的List 屬于 java.util.ArrayList 能進(jìn)行正常的增刪查操作
        List<String> strList = Stream.of(userIds).collect(Collectors.toList());
        return  strList;
    }

    /**
     * jdk8 將集合轉(zhuǎn)換成Map涮坐，其中用戶ID作為主鍵key,如果集合對(duì)象有重復(fù)的key,以第一個(gè)匹配到的為主
     * @param userList
     * @return
     *
     * 第一個(gè)參數(shù)：表示 key
     * 第二個(gè)參數(shù)：表示 value
     * 第三個(gè)參數(shù)：表示某種規(guī)則
     * 上文中的Collectors.toMap(User::getUserId, v -> v, (k1,k2) -> k1)凄贩，表達(dá)的意思就是將userId的內(nèi)容作為key，v -> v是表示將元素user作為value袱讹，
     * 其中(k1,k2) -> k1表示如果存在相同的key疲扎，將第一個(gè)匹配的元素作為內(nèi)容昵时，第二個(gè)舍棄!
     *
     */
    public static Map<String, User> getMap(List<User> userList){
        Map<String, User> userMap = userList.stream().collect(Collectors.toMap(User::getUuid, v -> v, (k1, k2) -> k1));
        return userMap;
    }


    /**
     * jdk8 將集合轉(zhuǎn)換成Map，將相同的key椒丧，加入到一個(gè)集合中壹甥，實(shí)現(xiàn)分組
     * @param userList
     * @return
     */
    public static Map<String, List<User>> getMapGroup(List<User> userList){
        Map<String, List<User>> userMap = userList.stream().collect(Collectors.groupingBy(User::getUuid));
        return userMap;
    }
}