FiboGenerator.java

public class FiboGenerator implements Iterable<BigInteger>, Iterator<BigInteger> {

    BigInteger avantDernier = BigInteger.ZERO;
    BigInteger avantAvantDernier = BigInteger.ONE ;

    @Override
    public Iterator<BigInteger> iterator() {
        return this;
    }

    @Override
    public boolean hasNext() {
        return true;
    }

    @Override
    public BigInteger next() {
        BigInteger next = avantAvantDernier.add(avantDernier);
        this.avantAvantDernier = this.avantDernier;
        this.avantDernier = next;
        return next;
    }
}

// Execution :

public class Main {
    public static void main(String[] args) {
        for (BigInteger elt : new FiboGenerator()){
            System.out.println(elt.toString());
            if (elt.compareTo(new BigInteger("1000000")) == 1)
                break;
        }
    }
}