flipLines.java

import java.util.Scanner;
import java.io.*;
 
public class flipLines {
	public static void main(String [] args) {

		
		Scanner input = new Scanner(System.in);
		Scanner file = new Scanner(new File(toFlip.txt));

		int lineCounter = 1;
		String[] lineString;
		String[] flippedLineString;


		while (file.nextLine() != null){
			lineCounter = lineCounter+1;
		}

		linestring = new String[lineCounter];

		//for loop fills the lineString array with elements of the text file
		for (int i=0; i<lineCounter i++){
			lineString[i] = file.nextLine();
		}

		for (int j=0; j<lineCounter; j++){
			flippedLineString[i]   = lineString[i+1];
			flippedLineString[i+1] = lineString[i];

		}

		// WRITE TO File

			try{
				PrintWriter writeFile = new PrintWriter(
										new BufferedWriter(
										new FileWriter(toFlip.txt)));

				for (int k=0; k<lineCounter; k++ ){
					writeFile.println(flippedLineString[k]);
				}
					writeFile.close;

			}
			catch (IOException e){
				System.err.println("There seems to be an error");

			}