Invert a text file Learn programming Java

Lesson:

File Management


Exercise:

Invert a text file 22


Objetive:

Create a program to "invert" the contents of a text file: create a file with the same name ending in ".tnv" and containing the same lines as the original file but in reverse order (the first line will be the last one, the second will be the penultimate, and so on, until the last line of the original file, which should appear in the first position of the resulting file).

Hint: the easiest way, using only the programming structures we know so far, is reading the source files two times: the first time to count the amount of lines in the file, and the second time to store them in an array.


Code:

package InvertText;
import java.util.*;

public class Main
{
	public static void main(String[] args)
	{
		System.out.print("Enter name file: ");
		String fileName = new Scanner(System.in).nextLine();

		if ((new java.io.File(fileName)).isFile())
		{
			java.io.FileReader myfileRd = new java.io.FileReader(fileName);
		java.io.BufferedReader myfileRdBufferedReader = new java.io.BufferedReader(myfileRd);
			String line;
			int countLines = 0;

			// Count lines of file
			do
			{
				line = myfileRdBufferedReader.readLine();
				if (line != null)
				{
					countLines++;
				}
			} while (line != null);
			myfileRd.close();

			// Write of array of lines
			String[] lines = new String[countLines];
			int countLine = 0;
			myfileRd = new java.io.FileReader(fileName);
			line = "";
			do
			{
				line = myfileRdBufferedReader.readLine();
				if (line != null)
				{
					lines[countLine] = line;
					countLine++;
				}
			} while (line != null);
			myfileRd.close();

			// Write of file
			java.io.FileWriter myfileWr = new java.io.FileWriter(fileName + ".tnv");

			for (int i = lines.length - 1; i > 0; i--)
			{
				myfileWr.write(lines[i] + System.lineSeparator());
			}

			myfileWr.close();

		}
		else
		{
			System.out.println("The file no exists.");
		}
	}
}