Java读取Json文件

{"__source__":"","__source___0":"","__tag__:__instance_id__":"ba11a23ebc39f1c0-5de8230d68621-3a8defe","__tag__:__job__":"sql-1650437116-774867","__tag__:__project__":"k8s-aplus-prod-1","__tag__:__schedule_time__":"1652025600","__tag__:__trigger_time__":"1652025630","__time__":"1651939200","__topic__":"","cnt":"101","keyword":"护发素"}
{"__source__":"","__source___0":"","__tag__:__instance_id__":"ba11a23ebc39f1c0-5de8230d68621-3a8defe","__tag__:__job__":"sql-1650437116-774867","__tag__:__project__":"k8s-aplus-prod-1","__tag__:__schedule_time__":"1652025600","__tag__:__trigger_time__":"1652025630","__time__":"1651939200","__topic__":"","cnt":"102","keyword":"厨房"}
{"__source__":"","__source___0":"","__tag__:__instance_id__":"ba11a23ebc39f1c0-5de8230d68621-3a8defe","__tag__:__job__":"sql-1650437116-774867","__tag__:__project__":"k8s-aplus-prod-1","__tag__:__schedule_time__":"1652025600","__tag__:__trigger_time__":"1652025630","__time__":"1651939200","__topic__":"","cnt":"102","keyword":"纸巾"}

这是一个文件
json 数据 开头和结尾不带[ ] ，因为从文件转换成JSONArray 要中括号 且每个json要有，逗号隔开

实现一
思路 先把文件按照字符读出来 使用StringBuffer拼接。（会把换行符也写进去）
后以换行符切割 把每个切割得到的字符转换成JSONObject， 后该干啥就干啥

        File file1 = new File(filename);
    private static List test(File file) throws IOException{
        long start = System.nanoTime();
        List keyword = new LinkedList<>();
        Reader reader = new InputStreamReader(new FileInputStream(file), "Utf-8");
        //读取每个字符char
        int ch = 0;
        StringBuffer sb = new StringBuffer();
        while ((ch = reader.read()) != -1) {
            sb.append((char) ch);
        }

        reader.close();
        String jsonStr = sb.toString();
        //以换行符切割字符串
        String[] str = jsonStr.split("n");
        for (int i = 0; i < str.length; i++) {
            //System.out.println(JSONObject.parseObject(str[i]).getString("keyword"));
   //将每个字符串转为json对象  JSONObject.parseObject(String str);       keyword.add(JSONObject.parseObject(str[i]).getString("keyword"));
        }
        long end  = System.nanoTime();
        System.out.println("time"+(end-start));
        return keyword;
    }

第二种
BufferedReader.readLine() 他能以按行的形式去读取 遇到空格或者回车返回`
刚好每一行就是一个JSON字符串。
源码如下

 charLoop:
                for (i = nextChar; i < nChars; i++) {
                    c = cb[i];
                    //遇到回车或者空格就结束循环遍历
                    if ((c == 'n') || (c == 'r')) {
                        eol = true;
                        break charLoop;
                    }
                }

public static List readFile(){
        long start = System.nanoTime();
        List keyWordList = new ArrayList<>();
        FileReader fr = null;
        BufferedReader br = null;
        try {
            fr = new FileReader("filename");
            br = new BufferedReader(fr);
            String line = "";
            //读取每一行的数据
            while ( (line = br.readLine()) != null) {
                JSONObject lineJson = JSONObject.parseObject(line);
                keyWordList.add(lineJson.getString("keyword"));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            try {
                br.close();
                fr.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        long end  = System.nanoTime();
        System.out.println("time"+(end-start));
        return keyWordList;
    }