Consider static sample method on each algorithm

[gstamatelat]

For example

public static <E> Collection<E> execute(Collection<E> population, int sampleSize, Random random) {
    final LiLSampling<E> sampling = new LiLSampling<>(sampleSize, random);
    sampling.feed(population);
    return sampling.sample;
}

This way, the caller would be able to get the mutable sample collection and not reuse the instance.