import java.io.BufferedWriter;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;

public class MultiThreadHW {

    public static void main(String[] args) {
        int numberOfFiles = extra.Console.readInt("How many files do you want (1-10)? ");
        while (numberOfFiles < 1 || numberOfFiles > 10) {
            numberOfFiles = extra.Console.readInt("Invalid answer, choose a number between 1 and 10 ");
        }

        createFiles(numberOfFiles);
        long sumOfRowsFromAllFiles = 0;
        List<FileThread> filethreads = new ArrayList<>();

        try {
            for (int i = 0; i < numberOfFiles; i++) {
                filethreads.add(new FileThread(new FileReader("C:\\workspace\\MultiThreadHW\\text" + i + ".txt")));
                filethreads.get(i).start();
                filethreads.get(i).join();
            }

            for (FileThread filethread : filethreads) {
                sumOfRowsFromAllFiles += filethread.getNumberOfRows();
            }

            System.out.println("The number of rows in all files is: " + sumOfRowsFromAllFiles);

        } catch (FileNotFoundException ex) {
            Logger.getLogger(MultiThreadHW.class.getName()).log(Level.SEVERE, null, ex);
        } catch (InterruptedException ex) {
            Logger.getLogger(MultiThreadHW.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

    public static void createFiles(int numberOfFiles) {
        int i = 0;

        while (i < numberOfFiles) {
            try {
                BufferedWriter writer = new BufferedWriter(new FileWriter("C:\\workspace\\MultiThreadHW\\text" + i + ".txt"));
                for (int j = 1; j <= 100000 + (int) (Math.random() * numberOfFiles + 1); j++) {
                    writer.write(j + ". Line.");
                    writer.newLine();
                }

                writer.close();
            } catch (FileNotFoundException ex) {
                Logger.getLogger(MultiThreadHW.class.getName()).log(Level.SEVERE, null, ex);
            } catch (IOException ex) {
                Logger.getLogger(MultiThreadHW.class.getName()).log(Level.SEVERE, null, ex);
            }
            i++;
        }
    }
}

public class FileThread extends Thread {

    private BufferedReader reader;
    private int numberOfRows;

    public FileThread(FileReader fileReader) {
        this.reader = new BufferedReader(fileReader);
        numberOfRows = 0;
    }

    public int getNumberOfRows() {
        return numberOfRows;
    }

    @Override
    public void run() {
        try {
            while (reader.readLine() != null) {
                numberOfRows++;
            }
            reader.close();
        } catch (IOException ex) {
            Logger.getLogger(MultiThreadHW.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}