code: public static void empty(String parameter, String name) {
  		if (parameter == null || !parameter.isEmpty()) {
  			throw new IllegalArgumentException(name + " is null or not empty.");
  		}
  	}
docs: Test if string parameter is strictly empty, that is, not null but empty.
  
  @param parameter invocation string parameter,
  @param name the name of invocation parameter.
  @throws IllegalArgumentException if <code>parameter</code> is null or not empty.