public C fitness() {
		if (_fitness == null) {
			throw new NoSuchElementException(
				"Phenotype has no assigned fitness value."
			);
		}

		return _fitness;
	}
Return the fitness value of this {@code Phenotype}.

@see #fitnessOptional()

@return The fitness value of this {@code Phenotype}.
@throws NoSuchElementException if {@link #isEvaluated()} returns
        {@code false}
jenetics/src/main/java/io/jenetics/Phenotype.java