BufferedReader not reading entire file

Question

The objective of the code is to read a file character by character, converting each to lowercase and replacing non-alphabets with a space. There are 500 lines in the original file but the edited file ends abruptly.

        File fileToBeModified = new File(filePath);         
        BufferedReader reader = null;
         
        FileWriter writer = null;
         
        try
        {
            reader = new BufferedReader(new FileReader(fileToBeModified));
             
            char single;
            String lowercase="";
            int a = reader.read();
            writer = new FileWriter(fileToBeModified);
            while(a!=-1){
                single = (char) a;
                String s = String.valueOf(single);
                if (a>=65 && a<=90 || a>=97 && a<=122)
                    lowercase = s.replace(s, s.toLowerCase());
                
                else if(s.equals("0")==false && s.equals("1")==false && s.equals("'")==false)
                    lowercase = s.replace(s, " ");
                    
                writer.write(lowercase);
                a = reader.read();
            }
             
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
        finally
        {
            try
            {
                //Closing the resources
                 
                reader.close();
                 
                writer.close();
            } 
            catch (IOException e) 
            {
                e.printStackTrace();
            }
        }

How can I get the program to perform the actions on the entire file?

Here is a part of the file. It is a dataset 500 lines of restaurant reviews and the rest of the file is in the same format.

Wow... Loved this place.    1
Crust is not good.  0
Not tasty and the texture was just nasty.   0
Stopped by during the late May bank holiday off Rick Steve recommendation and loved it. 1
The selection on the menu was great and so were the prices. 1
Now I am getting angry and I want my damn pho.  0
Honeslty it didn't taste THAT fresh.)   0
The potatoes were like rubber and you could tell they had been made up ahead of time being kept under a warmer. 0
The fries were great too.   1
A great touch.  1
Service was very prompt.    1
Would not go back.  0
The cashier had no care what so ever on what I had to say it still ended up being wayyy overpriced. 0
I tried the Cape Cod ravoli, chicken,with cranberry...mmmm! 1
I was disgusted because I was pretty sure that was human hair.  0
I was shocked because no signs indicate cash only.  0
Highly recommended. 1
Waitress was a little slow in service.  0
This place is not worth your time, let alone Vegas. 0
did not like at all.    0
The Burrittos Blah! 0
The food, amazing.  1

Answer 1

I have tried to simplify the solution leveraging Java8, stream and regular expression.

readAllLines : This method read all lines from a file. Bytes from the file are decoded into characters using the UTF-8 charset. Refer to the doc : class-files for details.

Note : You can further change regular expressions as per your requirement / use-case.

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

public class FileRead
{
    public static void main(String[] args) throws IOException {
        generateArrayListFromFile("lines.txt");
    }

    public static ArrayList<String> generateArrayListFromFile(String filename) throws IOException {

        List<String> result = Files.readAllLines(Paths.get(filename));

        result.stream().map(String::toLowerCase).collect(Collectors.toList());

        List<String> withoutNumbers = new ArrayList<>();

        for (String s : result) {

            withoutNumbers.add(s.replaceAll("\\d", ""));
        }   
        System.out.println(withoutNumbers);
        return (ArrayList<String>) withoutNumbers;
    }
}

Answer 2

A file may contain different types of characters. To read this character, sometimes BufferedReader.reader() may throw an exception. I tried to execute your code using your input format. But that time without any issue it executed. So my suggestion is to use an additional try-catch block when to read and to write to file. Moreover, String operation is very costly and not memory efficient. I modify your code and share it here, hope it will be helpful to you.

        String filePath = "hello.txt";
        File fileToBeModified = new File(filePath);
        System.out.println(fileToBeModified.exists());
        BufferedReader reader = null;

        FileWriter writer = null;

        try {
            reader = new BufferedReader(new FileReader(fileToBeModified));

            char single;
            //String lowercase = "";
            char lowercase = ' ';
            int a = reader.read();
            writer = new FileWriter(fileToBeModified);
            while (a != -1) {
                single = (char) a;
                //String s = String.valueOf(single);
                if (a >= 65 && a <= 90 || a >= 97 && a <= 122)
                    lowercase = Character.toLowerCase(single);//s.replace(s, s.toLowerCase());

                //else if (s.equals("0") == false && s.equals("1") == false && s.equals("'") == false)
                else if(single != '0'&& single != '1' && single != '\'' )
                    lowercase = ' ';
                
                //additional try-catch block
                try {
                    writer.write(lowercase);
                    a = reader.read();
                }catch(Exception ex) {
                    ex.printStackTrace();
                }
            }

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                // Closing the resources
                reader.close();

                writer.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }