Read lines of a text file, From bottom to top

Question

read the last row first,
from bottom to top,
how to do it?
Thanks for help

Answer 1

If the index.txt contains
1
2
3I want to save it as
3
2
1But I got is
1
2
3 3 2 1Please see my code, thanks
import java.io.*;
import java.util.List;
import java.util.ArrayList;
public class Reverse {
    private String[] x;
    public void process(String dir) {
        try {
         File f1 = new File(dir,"index.txt");
                BufferedReader br = new BufferedReader(new FileReader(f1));
                String line;
                List<String> idList = new ArrayList<String>();
                while (((line=br.readLine())!=null)){
                    idList.add(line);
                x = idList.toArray(new String[idList.size()]);
                f1.delete();
        catch (Exception e)
               System.err.println("File input error");
               e.printStackTrace ();
         try {    
         File fileIndex = new File(dir,"index.txt");
                 FileWriter outFileIndex = new FileWriter(fileIndex,true);
                 BufferedWriter outIndex = new BufferedWriter(outFileIndex);
                 for (int i = x.length-1 ; i>0; i--) {
                    StringBuffer buffer = new StringBuffer();
                    buffer.append(x);
buffer.append("\n");
outIndex.write(buffer.toString());
outIndex.flush();
catch (Exception e)
System.err.println("File input error");
e.printStackTrace ();
public static void main(String args[])
Reverse r = new Reverse();
r.process(args[0]);