code: public static LoggingSystem get(ClassLoader classLoader) {
  		String loggingSystem = System.getProperty(SYSTEM_PROPERTY);
  		if (StringUtils.hasLength(loggingSystem)) {
  			if (NONE.equals(loggingSystem)) {
  				return new NoOpLoggingSystem();
  			}
  			return get(classLoader, loggingSystem);
  		}
  		return SYSTEMS.entrySet().stream()
  				.filter((entry) -> ClassUtils.isPresent(entry.getKey(), classLoader))
  				.map((entry) -> get(classLoader, entry.getValue())).findFirst()
  				.orElseThrow(() -> new IllegalStateException(
  						"No suitable logging system located"));
  	}
docs: Detect and return the logging system in use. Supports Logback and Java Logging.
  @param classLoader the classloader
  @return the logging system