@Override
	public boolean isValid() {
		if (_valid == null) {
			final byte[] check = Bits.newArray(_validAlleles.length());
			_valid = _genes.forAll(g -> !getAndSet(check, g.alleleIndex()));
		}

		return _valid;
	}
Check if this chromosome represents still a valid permutation (or subset)
of the given valid alleles.
jenetics/src/main/java/io/jenetics/PermutationChromosome.java