Help. Concatenacao

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;

public class Main {
	
	public static void main(String[] args) {
        // TODO code application logic here
       try {
        BufferedReader in = new BufferedReader(new FileReader("teste.txt"));
            String str = "";
            String te = "";
            int i;
            while (in.ready()) {
                str = in.readLine();
                process(str);        
            }
            in.close();
    } catch (IOException e) {
    	System.out.println("Nao achou");
    }     
        }
	private static void process(String str) {
		// TODO Auto-generated method stub
		char A1,A2;
        StringBuffer str1 = new StringBuffer();
        int i;
        i = str.length();
        A1 = str.charAt(i-1);
        A2 = str.charAt(i-2);
    
        str1 = str1.append(A2);
        str1 = str1.append(A1);
        
        StringBuffer o = new StringBuffer();
        o.append(str1);
        System.out.println(o);	
	}    
}