Java: How to read a text file

Question

I want to read a text file containing space separated values. Values are integers. How can I read it and put it in an array list?

Here is an example of contents of t

Answer 1

Just for fun, here's what I'd probably do in a real project, where I'm already using all my favourite libraries (in this case Guava, formerly known as Google Collections).

String text = Files.toString(new File("textfile.txt"), Charsets.UTF_8);
List<Integer> list = Lists.newArrayList();
for (String s : text.split("\\s")) {
    list.add(Integer.valueOf(s));
}

Benefit: Not much own code to maintain (contrast with e.g. this). Edit: Although it is worth noting that in this case tschaible's Scanner solution doesn't have any more code!

Drawback: you obviously may not want to add new library dependencies just for this. ^{(Then again, you'd be silly not to make use of Guava in your projects. ;-)}

Answer 2

Look at this example, and try to do your own:

import java.io.*;

public class ReadFile {

    public static void main(String[] args){
        String string = "";
        String file = "textFile.txt";

        // Reading
        try{
            InputStream ips = new FileInputStream(file);
            InputStreamReader ipsr = new InputStreamReader(ips);
            BufferedReader br = new BufferedReader(ipsr);
            String line;
            while ((line = br.readLine()) != null){
                System.out.println(line);
                string += line + "\n";
            }
            br.close();
        }
        catch (Exception e){
            System.out.println(e.toString());
        }

        // Writing
        try {
            FileWriter fw = new FileWriter (file);
            BufferedWriter bw = new BufferedWriter (fw);
            PrintWriter fileOut = new PrintWriter (bw);
                fileOut.println (string+"\n test of read and write !!");
            fileOut.close();
            System.out.println("the file " + file + " is created!");
        }
        catch (Exception e){
            System.out.println(e.toString());
        }
    }
}

Answer 3

read the file and then do whatever you want java8 Files.lines(Paths.get("c://lines.txt")).collect(Collectors.toList());