Is it possible to merge iterators in Java?

Question

Is it possible to merge iterators in Java? I have two iterators and I want to combine/merge them so that I could iterate though their elements in one go (in same loop) rathe

Answer 1

I haven't written Java code in a while, and this got me curious to whether I've still "got it".

First try:

import java.util.Iterator;
import java.util.Arrays; /* For sample code */

public class IteratorIterator implements Iterator {
    private final Iterator is[];
    private int current;

    public IteratorIterator(Iterator... iterators)
    {
            is = iterators;
            current = 0;
    }

    public boolean hasNext() {
            while ( current < is.length && !is[current].hasNext() )
                    current++;

            return current < is.length;
    }

    public T next() {
            while ( current < is.length && !is[current].hasNext() )
                    current++;

            return is[current].next();
    }

    public void remove() { /* not implemented */ }

    /* Sample use */
    public static void main(String... args)
    {
            Iterator a = Arrays.asList(1,2,3,4).iterator();
            Iterator b = Arrays.asList(10,11,12).iterator();
            Iterator c = Arrays.asList(99, 98, 97).iterator();

            Iterator ii = new IteratorIterator(a,b,c);

            while ( ii.hasNext() )
                    System.out.println(ii.next());
    }
}

You could of course use more Collection classes rather than a pure array + index counter, but this actually feels a bit cleaner than the alternative. Or am I just biased from writing mostly C these days?

Anyway, there you go. The answer to you question is "yes, probably".