If all you have is the iterator, then no, there is no "better" way. If the iterator comes from a collection you could as that for size.
Keep in mind that Iterator is just an interface for traversing distinct values, you would very well have code such as this
new Iterator<Long>() {
final Random r = new Random();
@Override
public boolean hasNext() {
return true;
}
@Override
public Long next() {
return r.nextLong();
}
@Override
public void remove() {
throw new IllegalArgumentException("Not implemented");
}
};
or
new Iterator<BigInteger>() {
BigInteger next = BigInteger.ZERO;
@Override
public boolean hasNext() {
return true;
}
@Override
public BigInteger next() {
BigInteger current = next;
next = next.add(BigInteger.ONE);
return current;
}
@Override
public void remove() {
throw new IllegalArgumentException("Not implemented");
}
};