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年11月28日 02:27:59 2011年11月28日 10:18:11 Sleeping 
2011年11月28日 10:21:24 2011年11月28日 10:23:36 Toileting 
2011年11月28日 10:25:44 2011年11月28日 10:33:00 Showering 
2011年11月28日 10:34:23 2011年11月28日 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?

• Boris the Spider: stream.map(line -> line.split("\t")).map(v -> new MonitoredData(sd.parse(v[o]), sd.parse(v[1]), v[2]).collect(toList());
• Tobias Roloff: @Boris the Spider ...sd.parse(v[o])... should be ...sd.parse(v[0])... ;)
• Boris the Spider: SimpleDateFormat sd. You wrote the code...

Answer 1

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.

• Ousmane D.: @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.
• Boris the Spider: Hmm - fair point - does beg the question of why the SDF is there to begin with... (have a +1)
• Ousmane D.: @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.
• Holger: Using "\t" as regex is not wrong. "\\t" is a special-character pattern referring to <tab> whereas "\t" just matches the <tab> character literally. The result is the same.