Generation in Conways game of life

Generation.java

package game;

public class Generation {

  private LivingCells livingCells;
  private Rules rules;

  public Generation(LivingCells cells, Rules rules) {
    this.livingCells = cells;
    this.rules = rules;
  }

  public boolean isExtinct() {
    return livingCells.empty();
  }

  public Generation produceNextGeneration() {
    LivingCells next = new LivingCells();

    addSurvivors(next);

    addNewCells(next);

    return new Generation(next, rules);
  }

  private void addSurvivors(LivingCells next) {
    for (Cell cell : livingCells) {
      if (willSurvive(cell))
        next.add(cell);
    }
  }

  private void addNewCells(LivingCells next) {
    Cells notAliveNeighbors = livingCells.getNotAliveNeighbors();

    for (Cell cell : notAliveNeighbors) {
      if (willBeBorn(cell))
        next.add(cell);
    }
  }

  private boolean willSurvive(Cell cell) {
    return rules.shouldStayAlive(livingCells
          .getAliveNeighborsNumberFor(cell));
  }

  private boolean willBeBorn(Cell cell) {
    return rules.shouldBeBorn(livingCells
          .getAliveNeighborsNumberFor(cell));
  }

  @Override
  public String toString() {
    return "[" + livingCells.toString() + "]";
  }

  @Override
  public boolean equals(Object obj) {
    if (this == obj)
      return true;
    if (obj == null)
      return false;
    if (getClass() != obj.getClass())
      return false;
    Generation other = (Generation) obj;
    if (livingCells == null) {
      if (other.livingCells != null)
        return false;
    } else if (!livingCells.equals(other.livingCells))
      return false;
    return true;
  }
}