public static Logger getLogger() throws Exception{
		
		if (filename == null){
			throw new Exception("Cannot initialice Logger: Filename not defined.");
		}
		if (level == null){
			level = Level.SEVERE;
		}
		
		if (logger == null){
			try{
				createLogger();
			}
			catch(IOException e){
				throw new Exception("Cannot initialice Logger.\nIOException:" + e.getMessage());
			}
			
		}
		return logger;
	}