code: private Map<String, String> getCustomMap(Pattern keyPattern) {
  		Map<String, String> map = new HashMap<>();
  
  		for (Iterator<Object> it = props.keySet().iterator(); it.hasNext();) {
  			String key = (String) it.next();
  			Matcher matcher = keyPattern.matcher(key);
  			if (matcher.matches()) {
  
  				String id = matcher.group(2);
  				String propertyValue = props.getProperty(key);
  				map.put(id, propertyValue);
  			}
  		}
  		return map;
  	}
docs: Returns the map, where the key is the 2 group of the pattern and the
  value is the property value
  
  @param keyPattern
  the pattern of the key
  @return the map.