@Override
	public int compareTo(final CharacterGene that) {
		return Character.compare(_allele, that._allele);
	}
@see java.lang.Character#compareTo(java.lang.Character)
@param that The other gene to compare.
@return value 0 if the argument Character is equal to this Character;
        a value less than 0 if this Character is numerically less than
        the Character argument; and a value greater than 0 if this
        Character is numerically greater than the Character argument
        (unsigned comparison). Note that this is strictly a numerical
        comparison; it is not local-dependent.
jenetics/src/main/java/io/jenetics/CharacterGene.java