Java stream split lines and store in different objects

Question

I'm trying to understand java 8's Streams. Currently, I have a .txt file with this format:

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

Those 3 "items" are always separated by a TAB. What i want to do is to declare a class, MonitoredData, with attributes(of type String)

start_time  end_time  activity

What i want to achieve is to read the data from the file using streams and create a list of objects of type MonitoredData.

After reading about Java 8 i managed to write the following but then I reached a dead end

public class MonitoredData {
    private String start_time;
    private String end_time;
    private String activity;

    public MonitoredData(){}

    public void readFile(){
        String file = "Activities.txt";  //get file name
        //i will try to convert the string in this DateFormat later on
        SimpleDateFormat sd = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");                                      

        //Store the lines from the file in Object of type Stream
        try (Stream<String> stream = Files.lines(Paths.get(file))) {  

            stream.map(line->line.split("\t"));


        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Well, somehow I have to split the each line and store it in a Object appropriate to MonitoredData's attribute. How do i do that?

`stream.map(line -> line.split("\t")).map(v -> new MonitoredData(sd.parse(v[o]), sd.parse(v[1]), v[2]).collect(toList());` — Boris the Spider, May 18 '18 at 19:30
@Boris the Spider ...sd.parse(v[**o**])... should be ...sd.parse(v[**0**])... ;) — Tobias Roloff, May 18 '18 at 19:37

Ousmane D. · Accepted Answer · 2018-05-18T21:47:17.503

6

All you have to do is add another map operation as shown below:

 stream.map(line -> line.split("\t"))
       .map(a -> new MonitoredData(a[0], a[1], a[2]))
       .collect(Collectors.toList());

then collect to a list with the toList collector.

edited May 18 '18 at 21:47

answered May 18 '18 at 19:37

Ousmane D.

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@BoristheSpider not sure if that's what the OP wants as in the `MonitoredData` class `start_time` and `end_time` are strings whereas `SimpleDateFormat.parse` will yield a `Date` instance. – Ousmane D. May 18 '18 at 19:41
Hmm - fair point - does beg the question of why the SDF is there to begin with... (have a +1) – Boris the Spider May 18 '18 at 19:42
@BoristheSpider Thanks!. the OP mentioned "i will try to convert the string in this DateFormat later on" , so I am assuming the `SimpleDateFormat` instance is for later operations that they want to perform. – Ousmane D. May 18 '18 at 19:43
2

Using `"\t"` as regex is not wrong. `"\\t"` is a special-character pattern referring to whereas `"\t"` just matches the character literally. The result is the same. – Holger May 18 '18 at 21:39

Java stream split lines and store in different objects

1 Answers1