拆分流并从文本文件放入列表 [英] Split stream and put into list from text file

问题描述

如何将我从文本文件中读取的所有元素放入 ArrayList <MonitoredData > 使用streams，其中monitoredData 类有这3 个私有变量:私有日期开始时间、日期结束时间、字符串活动标签;

How can I put all the elements I read from a text file into an ArrayList < MonitoredData > using streams, where monitoredData class has these 3 private variables: private Date startingTime, Date finishTime, String activityLabel;

文本文件活动.txt 如下所示:

The text File Activities.txt looks like this:

2011-11-28 02:27:59     2011-11-28 10:18:11     Sleeping        
2011-11-28 10:21:24     2011-11-28 10:23:36     Toileting   
2011-11-28 10:25:44     2011-11-28 10:33:00     Showering   
2011-11-28 10:34:23     2011-11-28 10:43:00     Breakfast

等等......

前 2 个字符串由一个空格分隔，然后是 2 个制表符，再次是一个空格，2 个制表符.

The first 2 strings are separated by one blank space, then 2 tabs, one space again, 2 tabs.

String fileName = "D:/Tema 5/Activities.txt";

    try (Stream<String> stream = Files.lines(Paths.get(fileName))) {

        list = (ArrayList<String>) stream
                .map(w -> w.split("		")).flatMap(Arrays::stream) 
                .collect(Collectors.toList());

    } catch (IOException e) {

        e.printStackTrace();
    }

推荐答案

你需要引入一个工厂来创建MonitoredData，在示例中我使用一个Function从 String[] 创建一个 MonitoredData:

you need introduce a factory to create the MonitoredData, in example I'm using a Function to create a MonitoredData from String[]:

Function<String[],MonitoredData> factory = data->{
   DateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
   try{
     return new MonitoredData(format.parse(data[0]),format.parse(data[1]),data[2]);
     //                       ^--startingTime       ^--finishingTime      ^--label
   }catch(ParseException ex){
     throw new IllegalArgumentException(ex);
   }
};

THEN 您的代码对流的操作应该如下所示，并且您不需要使用 Collectors#toCollection:

THEN your code operate on a stream should be like below, and you don't need casting the result by using Collectors#toCollection:

list = stream.map(line -> line.split("		")).map(factory::apply)  
             .collect(Collectors.toCollection(ArrayList::new));

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