code: public void addAllIfNotExist(Properties properties) {
      for (String key : properties.stringPropertyNames()) {
        if (!this.specProperties.containsKey(key) && !this.commonProperties.containsKey(key)) {
          this.specProperties.setProperty(key, properties.getProperty(key));
        }
      }
    }
docs: Add properties in a {@link Properties} instance that are not in the current instance.
  
  @param properties a {@link Properties} instance