唯一一道IO题

这是唯一一道IO题，能做出来说明已经把IO完全掌握了。

import java.io.*;
 
 
public class FileUtils{
public static String readFirstLine(String a){
FileReader f1 = null;
FileWriter  out = null;
String sum = null;
try {
f1 = new FileReader(a);
out = new FileWriter(a);
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
BufferedReader in = null;
BufferedWriter ou = new BufferedWriter(out);
try{
in = new BufferedReader(f1);
String x = in.readLine();
for(int i=0;i<x.length();i++){
sum=sum+x.substring(x.length()-i-1,x.length()-i);
}
ou.write(sum);
ou.flush();
}catch(Exception e){
}
return sum;
}
public static String readLine(String a,int b){
FileReader f1 = null;
FileWriter  out = null;
try {
f1 = new FileReader(a);
out = new FileWriter(a);
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
BufferedReader in = null;
BufferedWriter ou = new BufferedWriter(out);
try{
in = new BufferedReader(f1);
String x = "";
for(int i=1;i<=b;i++){
if(b==i){
x=in.readLine();
}in.readLine();
}
String sum = null;
for(int i=0;i<x.length();i++){
sum=sum+x.substring(x.length()-i-1,x.length()-i);
}
ou.write(sum);
}catch(Exception e){
}
return a;
}
}