final String userSourcePath = System.getProperty( "user.dir" ) + "/temp.txt";
final String userDestPath = System.getProperty( "user.dir" ) + "/temp2.txt";
final Path source = GeneralPathImpl.create( fsProvider.getFileSystem( URI.create( "file:///" ) ), userSourcePath, false );
final Path dest = GeneralPathImpl.create( fsProvider.getFileSystem( URI.create( "file:///" ) ), userDestPath, false );
final OutputStream stream = fsProvider.newOutputStream( source );
stream.write( 'a' );
stream.close();
long lenght = source.toFile().length();
fsProvider.move( source, dest );