private InputStream startExternal(String fileName) {
		InputStream result = null;
		try {
			String extension = getExtension(fileName);
			String command = externalSupport.get(extension).replace(
					FILEPLACEHOLDER, fileName);
			Process externalProcess = Runtime.getRuntime().exec(command);
			result = externalProcess.getInputStream();
		} catch (IOException ignore) {
		}
		return result;
	}
private InputStream startExternal ( String fileName ) { InputStream result = null ; try { String extension = getExtension ( fileName ) ; String command = externalSupport . get ( extension ) . replace ( FILEPLACEHOLDER , fileName ) ; Process externalProcess = Runtime . getRuntime ( ) . exec ( command ) ; result = externalProcess . getInputStream ( ) ; } catch ( IOException ignore ) { } return result ; }
Start an external utility to unpack the the archive

@param fileName
@return InputStream to read the decompressed data