Question

Please write a java program with a input file "jabberwock.txt", and output the "output.txt" with following requirement.

You and your partner will be writing a simple Java program that implements some basic file I/O operations. You can use this code as the basis for some of your next project.

FIRST: Write code that prompts the user for the name of a text file, opens that file if it exists and reads the file one line at a time printing each line to the screen. You must implement the file read in a try/catch block rather than throwing the exception on the main method. The name of the text file you will be using is jabberwock.txt.

NEXT: Modify your code so that the program takes the name of two files from the command line, opens the first file if it exists for reading and the second file for writing and copies the text of the first file into the second file. As with the first step, you must implement this in a try/catch block with an appropriate error message in the catch block.

NEXT: Complete the method reverse that takes a String and returns a new String that is the original String reversed. Note that we did this method in the lab a few weeks ago, so if you have that code you can just paste it in here.

NEXT: Modify your code so that instead of printing each line to the file, it prints the reverse of each line to the output file using your reverse method.

FINALLY: Make a single change to your code so that instead of copying the file, it outputs the new file not just reversed, but with all characters transformed to uppercase letters. (HINT: Make use of String's toUpperCase() method for this).

Use the code skeleton below to start your code. Then look at the course notes on File I/O to fill in what you need in the skeleton. Your output to the screen should look like the following to match the test cases:

Enter a filename: jabberwock.txt
Enter an output file: output.txt

Answer 1

In your question, it is given to modify hence i put them under comments which you can remove and implement

import java.io.*;
class Reverse
{
String a="";
Reverse(String b)
{
a=b;
}
public String reverse()throws java.lang.NullPointerException
{
char[] a1 = a.toCharArray();
String b="";
for (int i = a1.length-1; i>=0; i--)
b=b+a1[i];
return b;
}
}
public class Main
{
public static String reverse(String a)
{
char[] a1 = a.toCharArray();
String b="";
for (int i = a1.length-1; i>=0; i--)
b=b+a1[i];
return b;
}   
public static void main(String []args)throws IOException, java.lang.NullPointerException
{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter a file name");
String input=br.readLine();
System.out.println("Enter output file name");
String output=br.readLine();
BufferedReader objReader = null;
BufferedReader objReader2 = null;
try
{
File file = new File(output);
BufferedWriter bw = null;
   if (!file.exists()) {
   file.createNewFile();
   }
FileWriter fw = new FileWriter(file);
   bw = new BufferedWriter(fw);
  
String strCurrentLine;
objReader = new BufferedReader(new FileReader(input));
objReader2 = new BufferedReader(new FileReader(input));
while ((strCurrentLine = objReader.readLine()) != null)
{
System.out.println(strCurrentLine);
bw.write(strCurrentLine);
}
/*System.out.println("Reverse order of strings");
Main m=new Main();
while ((strCurrentLine = objReader2.readLine()) != null)
{
System.out.println(m.reverse(strCurrentLine));
bw.write(strCurrentLine);
//bw.write(toUpperCase(strCurrentLine));
}*/
  
}
catch (IOException e)
{
e.printStackTrace();
}
/*finally
{
try
{
if (objReader != null)
objReader.close();
}
catch (IOException ex)
{
ex.printStackTrace();
}
}*/
}
}