Question

• JAVA single method Loop (for beginner)
• Name your class LoopsFiles
• Create a program that reads a list of names from a source file and writes those names to a CSV file.
• The source file name and target CSV file name should be requested from the user
• The source file can have a variable number of names so your program should be dynamic enough to read as many names as needed
• When writing your CSV file, the first row (header row) should be “Number, Name”.
• The final CSV should have the header row and a row with the sequential number, name read.
• The program should display an error message if the source file doesn’t exist.
• If the destination file exists the program should warn the user and prompt the user if they want to overwrite the existing file (Y/N).
  • The user should be prompted until they enter Y for yes to overwrite, or enter a unique name after answering N for the overwrite prompt.
• Submit your single .java file

Source file example:

John
Peter
Jane
Mary
Evelyn
Daniel

New CSV File example:

Number, Name
1,John
2,Peter
3,Jane
4,Mary
5,Evelyn
6,Daniel

Example Scenario 1 – Normal run:

Enter source file name: source.txt
Enter destination file name: destination.csv
Your file is ready!

Example Scenario 2 – File doesn’t exist:

Enter source file name: source.txt
Enter destination file name: destination.csv
Source file doesn’t exist!

Example Scenario 3 – Target file already exists (overwrite):

Enter source file name: source.txt
Enter destination file name: destination.csv
Target file already exists. Overwrite existing file? (Y/N): N
Enter destination file name: destination.csv
Target file already exists. Overwrite existing file? (Y/N): N
Enter destination file name: destination.csv
Target file already exists. Overwrite existing file? (Y/N): N
Enter destination file name: destination.csv
Target file already exists. Overwrite existing file? (Y/N): Y
Your file is ready!

Example Scenario 4 – Target file already exists (new name given):

Enter source file name: source.txt
Enter destination file name: destination.csv
Target file already exists. Overwrite existing file? (Y/N): N
Enter destination file name: destination.csv
Target file already exists. Overwrite existing file? (Y/N): N
Enter destination file name: destination2.csv
Your file is ready!

Answer 1

Please find the code below:

import java.io.*;
import java.util.ArrayList;
import java.util.Scanner;

public class LoopsFiles {

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

        Scanner sc = new Scanner(System.in);
        System.out.println("Enter source file name: ");
        String source = sc.next();
        ArrayList<String> arrayList = new ArrayList<>();
        try {
            File file = new File(source);
            Scanner scanner = new Scanner(file);
            while (scanner.hasNextLine()) {
                String data = scanner.nextLine();
                arrayList.add(data);
                System.out.println(data);
            }
            scanner.close();
        } catch (FileNotFoundException e) {
            System.out.println("Source file doesn’t exist!");
            e.printStackTrace();
        }

        while(true) {

            System.out.println("Enter destination file name: ");
            String destination = sc.next();

            File file = new File(destination);

            if (file.createNewFile()) {

                System.out.println("File has been created.");
                FileOutputStream fileOutputStream = new FileOutputStream(file);
                BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(fileOutputStream));

                bw.write("Number,Name");
                bw.newLine();
                for (int i=1;i<=arrayList.size();i++) {
                    String temp = i + "," + arrayList.get(i-1);
                    System.out.println(temp);
                    bw.write(temp);
                    bw.newLine();
                }

                System.out.println("Your file is ready!");
                break;

            } else {

                System.out.println("Target file already exists. Overwriting existing file? (Y/N):");
                String inp = sc.next();

                if(inp.equals("N")) {
                    continue;
                }
                else {
                    System.out.println("File has been created.");
                    FileOutputStream fileOutputStream = new FileOutputStream(file);
                    BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(fileOutputStream));

                    bw.write("Number,Name");
                    bw.newLine();
                    for (int i=1;i<=arrayList.size();i++) {
                        String temp = i + "," + arrayList.get(i-1);
                        System.out.println(temp);
                        bw.write(temp);
                        bw.newLine();
                    }

                    System.out.println("Your file is ready!");
                    break;
                }

            }

        }

    }
}