How to use BufferedReader in Java [closed]

Question

Sorry if this is an obvious question, but I can't seem to get it. I'm working on an assignment for a Data Structures course. It involves pulling data from a simple .dat file. We had never used any of the file-accessing options in Java before, so the professor just gave us the working code for that piece.

A class called FileReadExample creates a new BufferedReader object, opens a file, and then is supposed to kick out a bunch of data about that file. But I cannot access any of the data at all.

In a separate testMain file, I created a new FileReadExample object named fr and then attempted to print out things like fr.readLine() from there, but it tells me there is no such method.

I'm sure I'm missing something staggeringly easy.

The professor's code:

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;

public class FileReadExample
{
    public static void main(String[] args)
    {
        System.out.println("got here");
        try
        {
            BufferedReader in = new BufferedReader(new FileReader(new File("sample-file.dat")));
            System.out.println("File open successful!");

            int line = 0;
            for (String x = in.readLine(); x != null; x = in.readLine())
            {
                line++;
                System.out.println(x);
                if (line <= 3)
                {
                    String[] tokens = x.split(" ");
                    System.out.println("Number of tokens in line " + line + ": " + tokens.length);
                    System.out.println("The tokens are:");
                    for (String token : tokens)
                    {
                        System.out.println(token);
                    }
                }
                else
                {
                    String[] tokens = x.split("\\|");
                    System.out.println("Number of tokens in line " + line + ": " + tokens.length);
                    System.out.println("The tokens are:");
                    for (String token : tokens)
                    {
                        System.out.println(token);
                    }
                    Integer[] values = new Integer[tokens.length];
                    Integer sum = 0;
                    for (int i = 0; i < tokens.length; i++)
                    {
                        sum += Integer.parseInt(tokens[i]);
                    }
                    System.out.println("Sum: " + sum);
                }
            }
        } catch (IOException e)
        {
            System.out.println("File I/O error!");
        }
    }
}

Thanks.

Have goolged. And YouTubed. And searched here. By everything I can see, it should be working. The only thing that I found that could be the problem is that it is all contained in a try/catch. But I'm not sure why that matters. — Christopher Robinson
The code you just posted is working fine for me. Do you get an exception or any error message? — Matthias Herlitzius
It compiles, but when I run my test main the cursor blinks and the program ends. Nothing happens, even though the code has a bunch of printlns in it. I guess my question is how to call data from a BufferedReader object within a FileReadExample object created in a separate test main. — Christopher Robinson
Just sorted your formatting out. The easiest way I find with java => stackoverflow is to format it all properly in your favourite editor first then copy paste the code into a new file, select all lines and hit tab/indent to get it recognised as code when you post here. Then paste in from that. — JonnyRaa

Matthias Herlitzius Matthias Herlitzius · Accepted Answer · 2013-04-28T17:46:12

Try this to read a file:

BufferedReader reader = null;

try {
    File file = new File("sample-file.dat");
    reader = new BufferedReader(new FileReader(file));

    String line;
    while ((line = reader.readLine()) != null) {
        System.out.println(line);
    }

} catch (IOException e) {
    e.printStackTrace();
} finally {
    try {
        reader.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

How to use BufferedReader in Java [closed]

2 Answers