Salesforce Apex Fibonacci Generator

FibonacciGenerator.cls

public with sharing class FibonacciGenerator implements Iterable<Long> {
  private Integer howMany = 0;

  public FibonacciGenerator(Integer howMany) {
    this.howMany = howMany;
  }

  public Iterator<Long> iterator() {
    return new FibonacciIterator(howMany);
  }

  public class FibonacciIterator implements Iterator<Long> {
    private Integer generationGoal = 0;
    private Integer generationCount = 0;
    private List<Long> state = new List<Long>{ 0, 1 };

    public FibonacciIterator(Integer generationGoal) {
      this.generationGoal = generationGoal;
    }

    public Boolean hasNext() {
      return generationCount < generationGoal;
    }

    public Long next() {
      generationCount++;

      if (generationCount == 1) {
        return state[1];
      }

      Long tmp = state[1];
      state[1] = state[1] + state[0];
      state[0] = tmp;
      return state[1];
    }
  }
}

FibonacciGeneratorTest.cls

@IsTest
public with sharing class FibonacciGeneratorTest {
  @IsTest
  static void shouldGenerateFibonacci() {
    Integer howManyToGenerate = 33;

    for (Long num : new FibonacciGenerator(howManyToGenerate)) {
      system.debug(num);
    }
  }
}