selection algorithm

void produceNextGen() {
     LinkedList<Candidate> newPopulation = new LinkedList<Candidate>();

     //TODO: improve selection algorithm
     while(newPopulation.size()<populationSize) {
          int[] pos = getPermutation(4); // pick 4 candidates

          Candidate c1 = population.get(pos[0]);
          Candidate c2 = population.get(pos[1]);
          Candidate c3 = population.get(pos[2]);
          Candidate c4 = population.get(pos[3]);

          // pick 2 winners
          Candidate w1, w2;
          w1 = (c1.score() < c2.score()) ? c1 : c2;
          w2 = (c3.score() < c4.score()) ? c3 : c4;

          // cross-over the winners
          Candidate d1 = newChild(w1, w2, rnd.nextInt(numElements-2)+1);
          Candidate d2 = newChild(w1, w2, rnd.nextInt(numElements-2)+1);

          // mutate children
          if(rnd.nextInt(100)<mutationRatePercent) {
               mutate(d1);
          }
          if(rnd.nextInt(100)<mutationRatePercent) {
               mutate(d2);
          }

          // add children or the winners, based on the score
          newPopulation.add( (d1.score()<w1.score()) ? d1 : w1  );
          newPopulation.add( (d2.score()<w2.score()) ? d1 : w2  );

     }

     population = newPopulation;
     //Collections.sort(population, candidateComparator);
}