New to Java

I used a program which messed up all my ID3 tags. What i have been able to find so far on the forums allows me to read the ID3 tags but i now to write the correct tags back. I am not really sure how to use external packages so i was wondering if there was a way to do it without additional libraries. I use JGrasp at the moment, my current code is below which when the file is placed in the same directory as the files it will print out all ID3 data.

   import java.io.*; 

 
    public class ReadID3 { 
       public static void main(String[] arguments) { 
         try { 
            File song = new File("."); 
            File [] list = song.listFiles();
            for(int i=0;i<list.length;i++)
            {
               FileInputStream file = new FileInputStream(list); 

int size = (int)list[i].length(); 

file.skip(size - 128); 

byte[] last128 = new byte[128]; 

file.read(last128); 

String id3 = new String(last128); 

String tag = id3.substring(0, 3); 

if (tag.equals("TAG")) { 

System.out.println("Title: " + id3.substring(3, 32)); 

System.out.println("Artist: " + id3.substring(33, 62)); 

System.out.println("Album: " + id3.substring(63, 91)); 

System.out.println("Year: " + id3.substring(93, 97)); 

} 

else 

System.out.println(" does not contain" 

+ " ID3 info."); 

file.close();

} 

} 

catch (Exception e) { 

System.out.println("Error ? " + e.toString()); 

}



} 

}



Thanks for any help.