code: public static Properties singletonProperties(String propertyName, String propertyValue) {
      Properties singleProperty = new Properties();
      singleProperty.setProperty(propertyName, propertyValue);
      return singleProperty;
    }
docs: Factory method to construct a Singleton {@link Properties} object, a {@link Properties} instance containing
  only a single property and value.
  
  @param propertyName name of the property.
  @param propertyValue value of the property.
  @return a Singleton {@link Properties} instance.
  @see java.util.Properties