Question

Write a program that will write the contents of a text file backwards one character at a time. Your program should first ask for the text file name to be processed – and after verifying that the file exists, it should read the file into a StringBuilder buffer. Save the new file using the old filename appended with “Ver2-“ at the front. So for the file “MyStuff.txt” the file would be saved as Ver2-MyStuff.txt”. You can use any text file to test your work.

Answer 1

MainProgram.java

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;

public class MainProgram {
    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        System.out.print("Enter the file: ");
        String filename = console.next();
        File file = new File(filename);
        // checking if file exists or not
        if(!file.exists()){
            System.out.println("File not exists...");
            return;
        }
        StringBuffer buffer = new StringBuffer();
        try {
            // reading file and storing into buffer
            Scanner fileReader = new Scanner(new File(filename));
            while (fileReader.hasNextLine()){
                buffer.append(fileReader.nextLine()+"\n");
            }
        }catch (IOException e){
            System.out.println(e.getMessage());
            return;
        }
        String outFile = "Ver2-"+filename;
        try {
            // writing to file in backwards
            FileWriter writer = new FileWriter(new File(outFile));
            for(int i=buffer.length()-2; i>0; i-- )
                writer.write(buffer.charAt(i));
            writer.write("\n");
            writer.flush();
            writer.close();
            System.out.println("Output written to "+outFile);
        }
        catch (IOException e){
            System.out.println(e.getMessage());
        }

    }
}

// OUT

>javac MainProgram.java

>java MainProgram
Enter the file: words.txt
Output written to Ver2-words.txt