Part of Conway's Game of Life in Java pushing on the OO boundary

GameOfLifeOOX.java

protected Map<Cell, State> captureStateTransitions(Ecosystem ecosystem) {
	Map<Cell, State> stateTransitions = createSelfMinimizingMap();
	for (Cell cell : ecosystem.getCells()) {
		stateTransitions.put(cell, getRules().evaluate(ecosystem, cell));
	}
	return stateTransitions;
}


package gol.impl;

import gol.Cell;
import gol.Rules;
import gol.Ecosystem;
import gol.Rule;
import gol.Cell.State;

import java.util.Arrays;
import java.util.List;

public class DefaultRules implements Rules {

	private List<Rule> rules;

	public DefaultRules(Rule[] rules) {
		setRules(Arrays.asList(rules));
	}

	@Override
	public State evaluate(Ecosystem ecosystem, Cell cell) {
		State state = cell.getState();
		int liveNeighborCount = ecosystem.getNeighborCount(cell);

		for (int index = 0; state.equals(cell.getState()) && index < rules.size(); index++) {
			state = rules.get(index).evaluate(cell.getState(), liveNeighborCount);
		}

		return state;
	}

	@Override
	public void setRules(List<Rule> rules) {
		this.rules = rules;
	}

}


package gol.impl;

import static gol.Cell.State.DEAD;
import gol.Rule;
import gol.Cell.State;

public class ResurectableRule implements Rule {

	@Override
	public State evaluate(State state, int neighborCount) {
		return (DEAD == state && 3 == neighborCount) ? State.ALIVE : state;
	}

}


package gol.impl;

import static gol.Cell.State.ALIVE;
import gol.Rule;
import gol.Cell.State;

public class OverPopulatedRule implements Rule {

	@Override
	public State evaluate(State state, int neighborCount) {
		return (ALIVE == state && 3 < neighborCount) ? State.DEAD : state;
	}

}


package gol.impl;

import static gol.Cell.State.ALIVE;
import gol.Rule;
import gol.Cell.State;

public class UnderPopulatedRule implements Rule {

	@Override
	public State evaluate(State state, int neighborCount) {
		return (ALIVE == state && 2 > neighborCount) ? State.DEAD : state;
	}

}