文件数据读取，并按时间取最新结果

背景：

今天项目遇到一类场景，跟大家分享下解题过程：已知文件中一组数据如下：

 要求以user字段分组，并按time倒序，求出每人最新的结果。

分析思路：

1.文件读取

　　private static List<Map<String, String>> readDataFromFile(File file) {
        List<Map<String, String>> result = new ArrayList<>();
        String[] titles = new String[]{"id", "user", "address", "time"};
        try (BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(file), StandardCharsets.UTF_8))) {
            boolean firstLine = true;
            String data;
            while (null != (data = br.readLine())) {
                if (firstLine) {
                    firstLine = false;
                    continue;
                }

                String[] split = data.split("\\t");
                Map<String, String> map = new HashMap<>();
                for (int i = 0; i < split.length; i++) {
                    map.put(titles[i], split[i]);
                }
                result.add(map);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }

 2.数据排序：

　　private static void orderData(List<Map<String, String>> params) {
        Map<String, Map<String, String>> data = new HashMap<>();
        for (Map<String, String> item : params) {
            if (data.get("user") == null) {
                data.put(item.get("user"), item);
            } elseif (convertTime(data.get("user").get("time")) < convertTime(item.get("time"))) {
                data.put(item.get("user"), item);
            }
        }
    }

    private static long convertTime(String time) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        long result = 0L;
        try {
            Date date = sdf.parse(time);
            result = date.getTime();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }