Hello,
Simple method to read all files in direcory with subdirectories can be
implemented in this way:

public void readDirectory( String directoryPath ) throws Exception {
    addDirectory( new File( directoryPath ) );
}
private void addDirectory( File file ) throws Exception {
    if( file.isDirectory() ) {
        for( File f : file.listFiles() ) {
            addDirectory( f );
        }
    }
    else {
        addFile( file );
    }
}
You have to implement addFile( File file ); method.

Best Regards
Piotr Pejas