java - N-Queens Genetic Algorithm in regards to Selection and Mutation -

currently program works 8-queens, trying make work 22-queens. takes long when run algorithm 22 queens. believe problem may lie in way of selecting population or mutation.

private chromosome selectchromosome(chromosome[] population) {      random random = new random();     double x = random.nextdouble();     double accfit = 0;      (int = 0; < population.length; i++) {         accfit += population[i].fitness;         if (accfit > x && != 0) {             return population[i - 1];         }     }      return population[0]; } 

not sure if how mutation part

 private chromosome crossover(chromosome x, chromosome y) {     random random = new random();     int point = random.nextint(x.state.length);     int[] state = new int[x.state.length];     (int = 0; < point; i++) {         state[i] = x.state[i];     }      (int = point; < y.state.length; i++) {         state[i] = y.state[i];     }      // mutation     double mutaterate = random.nextdouble();     if (mutaterate <= 0.05) {         state[random.nextint(state.length)] = random.nextint(state.length);     }      return new chromosome(state); }