Simple Encryption (using Java) Technical Assessment 3

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

public class Task2{
  public static void main(String[] args) {

    // Read from file
    Scanner in = new Scanner(System.in);
    String data = "";
    int shift_size = 0;
    System.out.print("Enter file name (for input): ");
    String file_name = in.next();
    try {
        System.out.print("Shift size: ");
        shift_size = in.nextInt();
        File file_object = new File(file_name + ".txt");
        Scanner scanner_object = new Scanner(file_object);
        System.out.print("Message read from the file: ");
        while (scanner_object.hasNextLine()) {
            data += scanner_object.nextLine();
        }
        scanner_object.close();
        System.out.println(data);
    } catch (FileNotFoundException e) {
        System.out.println("An error occurred.");
        e.printStackTrace();
    }

    // Create file
    System.out.print("Enter file name (for output): ");
    file_name = in.next();
    try {
        File file_object = new File(file_name + ".txt");
        if (file_object.createNewFile()) {
            System.out.println("File created: " + file_name + ".txt");
        } else {
            System.out.println("File already exists.");
        }
    } catch (IOException e) {
        System.out.println("An error occurred.");
        e.printStackTrace();
    }

    // Write encrypted message to file
    try {
        FileWriter file_writer_object = new FileWriter(file_name + ".txt");
        StringBuilder new_string = new StringBuilder(data);
        for (int i = 0; i < (int) data.length(); i++) {
            if (new_string.charAt(i) != ' ') {
                new_string.setCharAt(i, (char) (new_string.charAt(i) + shift_size));
            }
        }
        System.out.print("Encrypted message: ");
        System.out.println(new_string);
        file_writer_object.write(new_string.toString());
        file_writer_object.close();
        System.out.println("Successfully encrypted!");
    } catch (IOException e) {
        System.out.println("An error occurred.");
        e.printStackTrace();
    }

  }
}