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Preparation Code for FILE IO

-------------------------------------------------------- চেম্পল কুড! ---------------------------------------------------------------
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.FileWriter;
import java.io.PrintWriter;

public class g {

    public static void main(String args[]) throws IOException {
        InputStreamReader cin = null;
        FileWriter fr = new FileWriter("INPUT.txt", true); // This is only creating, thats why not surronded with Try-catch
        PrintWriter pin = null;

        try {
            cin = new InputStreamReader(System.in);  // System.in , because we gonna input from console, not from any text File
            pin = new PrintWriter(fr,true);

            System.out.println("Enter characters, 'q' to quit.");
            char c;
            do {
                c = (char) cin.read();  // Converting BYTES to CHAR
                System.out.print(c);   // Consloe output

                pin.printf("%s", c);   // pin = Object of PrintWritter, works as like printf for FILE (text file basically)

            } while(c != 'q');



        }finally {
            if (cin != null) {
                cin.close();
                pin.close();
            }
        }
    }
}

-------------------------------------------------------------SUMMATION Ber korar CODE--------------------------------------------

Note: to run this code, you have to crate text file and put some value there, which will be named "source.txt"

import java.io.IOException;
import java.io.*;


public class File {

        public static void main(String[] args) throws IOException {

            BufferedReader br = null;
            //BufferedWriter bw = null;
            PrintWriter pw =    null;
            FileWriter fr = new FileWriter("output.txt");

            try {
                br = new BufferedReader(new FileReader("source.txt"));  // Reader means, "Go read from the file
                //"something.txt" this #Buff Buff thing can just only Read! no logical, storing or other to do!

               //bw = new BufferedWriter(new FileWriter("hudai.txt")); // This buff thing can write (can create 'someting.txt' )
                // with the help of FileWritter!

                pw = new PrintWriter(fr);  // This is PRINT_WRITER, kind of work as "println" for file FILE related balSal!


                String line;
                int sum = 0;
                while ((line = br.readLine()) != null)
                    sum = sum + Integer.parseInt(line);
               // System.out.println(sum);
                pw.println(sum);
               // bw.write(sum);

            }


            catch (Exception e) {
                e.printStackTrace();
            }


            br.close();
            pw.close();
           // bw.close();

        }
}

-----------------------------------------------FIND MAXIMUM VALUE FROM FILE -------------------------------------------------

Task : ei code tar output tmi console e na dekhye arekta File e dekhaba!

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

class LargeNum {


    public static void main(String[] args) {

        try {

            Scanner file = new Scanner(new File("numbers.txt"));  // We can also read a file by Scanner! ;)
            int largest = file.nextInt();   // This line telling tht, by nextInt it sayin go read Integer from file nd put those number into 'largest'
            // thats why we take ' int largest '

            while(file.hasNextInt()) {     // until found next line it will put one by one number in ' int number ' variable
                int number = file.nextInt();

                if(number > largest) {     // This is normal logic of finding maximum, like we do in real life, umuk ki umuker theke boro, boro hoile
                    // largest e rakhbe
                    largest = number;
                }

              System.out.println(number);

            }


            file.close();


            System.out.println("The largest number in the file is: " + largest);

        } catch(IOException e) {
            System.out.println(e.getMessage());
        }
    }
}

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