Copy Directory to Directory function ( backup)

[Nicolas Maisonneuve]

hy ,
i would like backup a index.

1) my first idea  is to make a system copy of all the files
but in the FSDirectory class,  there is no public method to know where is located the 
directory. A simple methode like 
public File getDirectoryFile() {
return directory; would be great;
}
2) so i decide to create a copy(Directory source, Directory target) method 
i seen the openFile() and createFile method but after i 
but i don't know how use it (see my function  , this function make a Exception )

    private void copy (Directory source, Directory target) throws IOException {
        String[] files=source.list();
        for(int i=0; i<files.length; i++) {
            InputStream in=source.openFile(files[i]);
            OutputStream out=target.createFile(files[i]);
            byte c;
            
            while((c=in.readByte())!=-1) {
                out.writeByte(c);
            }
            in.close();
            out.close();
        }

someone could help me please 
nico