Reading from a textfile to an arraylist

Question

I am supposed to read a few lines from a textfile and then store them in an arraylist. What is the best way to do such a thing? I must later be able to check each individual char.

1. read the file line by line, 2. put each line into an array list, 3. enjoy - did you try that already? — Thomas, Aug 21 '14 at 12:15
Come on... do a little research. http://stackoverflow.com/questions/2788080/reading-a-text-file-in-java — ortis, Aug 21 '14 at 12:17
You can try to use a `Scanner` to read the file line by line, and store them in an `ArrayList` as you read them. Is you use java 7 or 8, you can use `Files.readAllLines()`. — Florent Bayle, Aug 21 '14 at 12:17
possible duplicate of [How to read a large text file line by line using Java?](http://stackoverflow.com/questions/5868369/how-to-read-a-large-text-file-line-by-line-using-java) — fabian, Aug 21 '14 at 12:25
I guess I should've mentioned that I have already written the scanner thing, I am just unfamiliar with arraylist and didn't find what I was looking for when I googled it. — Fjodor, Aug 21 '14 at 12:33

Snehal Masne · Accepted Answer · 2014-08-21T12:50:10.570

0

Below is the simple snippet to do your work :

import java.io.File;
import java.util.ArrayList;
import java.util.Scanner;

public class ParseFile
    {            
        public static void main (String[] args)
        {
            Scanner scanner = null;
            ArrayList<String> store = new ArrayList<String>();
            try {
               scanner= new Scanner(new File("input.txt"));
                while (scanner.hasNext()) {
                    store.add(scanner.next());             
                }
            } catch (Exception e) {
                e.printStackTrace();            
            }
            finally{
                scanner.close();
            }

            for (String item : store) {
                System.out.println(item);
            }

        }
    }

edited Aug 21 '14 at 12:50

answered Aug 21 '14 at 12:20

Snehal Masne

3,403
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Come on. This _looks like_ Java, but does not even compile! Also, resource management is bad, i.e. you need to close the Scanner in a finally block. Finally, what do you expect to see in that System.out line at the end? The lines added to the ArrayList?! No way ... – mgaert Aug 21 '14 at 12:39
I said its snippet which could do it. I didnt intend to spoon feed. I just wanted to give the direction. – Snehal Masne Aug 21 '14 at 12:42
Sure, NP. Sorry for sounding harsh. – mgaert Aug 21 '14 at 13:02

score 0 · Answer 2 · answered Aug 21 '14 at 12:33

0

Use Apache commons io List lines = FileUtils.readLines(file, "UTF-8");

answered Aug 21 '14 at 12:33

mgaert

2,338
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fabian · Answer 3 · 2014-08-21T13:08:12.937

You can use Files.readAllLines(Path path)

Path path = //...
ArrayList<String> lines = new ArrayList<>(Files.readAllLines(path, Charset.defaultCharset()));

But using this approach, you'll have 2 lists in memory twice for a short time (i.e. during the execution of the ArrayList constructor).

If you don't need a modifiable list and don't need the list's type to be a ArrayList

List<String> lines = Files.readAllLines(path, Charset.defaultCharset());

works too, of course.

In java 8 you can of course use Streams too:

final ArrayList<String> lines = new ArrayList<>();
try (Stream<String> lineStream = Files.lines(path)) {
    lineStream.forEach(lines::add);
}

This way the lines are added to the list directly after they are read.

Good pointer! While Files is Java 7, readAllLines(Path) is only in Java 8, though ... need to use readAllLines(Path,CharSet) for Java 7... — mgaert, Aug 21 '14 at 13:05

score 0 · Answer 4 · answered Aug 21 '14 at 13:39

Try this:

 FileReader in = null;
    try
    {
        in = new FileReader("C:/Test.txt");
        BufferedReader br = new BufferedReader(in);
        ArrayList<String> lines = new ArrayList<String>();


        String s = br.readLine();
        while (s != null)
        {
            lines.add(s);
            s = br.readLine();

        }
        in.close();
    }
    catch (Exception ex)
    {
        Logger.getLogger(Read.class.getName()).log(Level.SEVERE, null, ex);
    }
}

Reading from a textfile to an arraylist

4 Answers4