CODEWITHSUNDEEP
javacsv
user5955313
user5955313

Reputation:

Reading lines into a list of lists

If the lines of my file contains elements separated by comma, Can I have a buffered reader automatically plug in the elements into a list?

Or do I do a readline then call a string.split method?

E.g. My file has. 

1, dog, abc, 10pm
2, cat, abc, 11pm

I want a list of lists out of my file so I can call the elements individually

Upvotes: 1

Views: 1055

Answers (3)

A4L
A4L

Reputation: 17595

The interface of BufferedReader does not support reading directly into a list and less into a list of lists. You will have at least to do the split by yourself.

As of java8 you can use BufferedReader.lines() to get stream of line which you will have to split, tranform to a list and add to a list of lists:

public List<List<String>> readAsListOfLists8(String file) throws IOException, FileNotFoundException {
    try (BufferedReader br = new BufferedReader(new FileReader(file))) {
        return br.lines().map(line -> Arrays.asList(line.split("[, ]+")))
            .collect(Collectors.toList());
    }
}

If you are running in java7 you can use Files.readAllLines to get a list of lines:

public List<List<String>> readAsListOfLists7(String file) throws IOException, FileNotFoundException {
    List<List<String>> ll = new ArrayList<>();
    for(String line : Files.readAllLines(Paths.get(file))) {
        ll.add(Arrays.asList(line.split("[, ]+")));
    }
    return ll;
}

For lower versions of java use your solution.

Upvotes: 0

Sнаđошƒаӽ
Sнаđошƒаӽ

Reputation: 17612

The easiest thing to do for your case is to read a line first, and then use split(), as all the lines are formatted exactly alike. And use ArrayList of String[] to make your list of lists.

Example using BufferedReader:

import java.util.*;
import java.io.*;

class Test {
    public static void main(String[] args) {
        ArrayList<ArrayList<String>> myList = new ArrayList<>();
        try {
            BufferedReader in = new BufferedReader(new FileReader("foo.txt"));
            while(in.ready()) {
                String line = in.readLine();
                String[] parts = line.split(", ");
                ArrayList<String> lineList = new ArrayList<>();
                for (String s : parts) {
                    lineList.add(s);
                }
                myList.add(lineList);
            }
        }
        catch(Exception e) {
        }

        for(ArrayList<String> elem : myList) {
            for(String item : elem) {
                System.out.print(item + " ");
            }
            System.out.println();
        }
    }
}

Using Scanner (incomplete example):

public static void main(String[] args) {
    try {
        Scanner in = new Scanner(new File("foo.txt"));
        in.useDelimiter(", ");

        while(in.hasNext()) {
            System.out.println(in.next());
        }
    }
    catch (Exception e) {
    }
}

Upvotes: 1

Gavin
Gavin

Reputation: 1767

Not to my knowledge, not unless you implement your own BufferedReader... though there might be one that takes lambda in Java 8

Upvotes: 0

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