refactoring example

appendMapEntries.java

// Helper function to append values if not already present in the Map
protected void appendMapEntries(Map<String, List<String>> map, String key, List<String> values) {
  for (String value : values) {
    List<String> existingValues = map.get(key);
    if (existingValues == null) {
      existingValues = new ArrayList<String>();
      map.put(key, existingValues);
    }
    else {
      existingValues.add(value);
    }
  }
}