Anyway, the problem is that I can’t really return just a single object from next(), and I also can’t have a Iterator take more than one type. So, any thoughts?
Obviously you are going to need a light-weight “pair” class. This is roughly analogous to the Map.Entry
inner class.
Here’s a rough cut at a generic solution:
public class ParallelIterator <T1, T2> implements Iterator<Pair<T1, T2>> {
public class Pair<TT1, TT2> {
private final TT1 v1;
private final TT2 v2;
private Pair(TT1 v1, TT2 v2) { this.v1 = v1; this.v2 = v2; }
...
}
private final Iterator<T1> it1;
private final Iterator<T2> it2;
public ParallelIterator(Iterator<T1> it1, Iterator<T2> it2) {
this.it1 = it1; this.it2 = it2;
}
public boolean hasNext() { return it1.hasNext() && it2.hasNext(); }
public Pair<T1, T2> next() {
return new Pair<T1, T2>(it1.next(), it2.next());
}
...
}
Note: this doesn’t explicitly deal with cases where the lists have different lengths. What will happen is that extra elements at the end of the longer list will be silently ignored.