Question

I’m working in a Genetic Algorithm and I want it as abstract as possible to be able to reuse the GA. I defined and implemented a Population Interface, and well it works, but I’m sure that’s not the best way to do it. I don’t have great experience with Java Generics. Is there an easier way of defining and implementing the Population interface (e.g. maybe avoid a cast conversion? avoid a new list in getChromosomes() ?)

public interface Population
{
    void addChromosomes(List<? extends Chromosome> chromosomes);

    List<Chromosome> getChromosomes();

    // More code here ...
}

public class TSPPopulation implements Population
{
    private List<TSPChromosome> chromosomes;

    @Override
    public void addChromosomes(List<? extends Chromosome> chromosomes) {
        for (Chromosome chromosome : chromosomes) {
            this.chromosomes.add((TSPChromosome) chromosome);
        }
    }

    @Override
    public List<Chromosome> getChromosomes() {
        List<Chromosome> newList = new ArrayList<Chromosome>();
        for (TSPChromosome chromosome : chromosomes) {
            newList.add(chromosome);
        }
        return newList;
    }
}

Answer 1

Use a Bounded Wildcard in your interface:

public interface Population<T extends Chromosome>{
    void addChromosomes(List<T> chromosomes);

    List<T> getChromosomes();
}

public class TSPPopulation implements Population<TSPChromosome>
{
    private List<TSPChromosome> chromosomes;

    @Override
    public void addChromosomes(List<TSPChromosome> chromosomes) {
...
    }

    @Override
    public List<TSPChromosome> getChromosomes() {
...    
    }

}