import java.util.*;
public class MergeIterators<T> implements Iterator<T> {
    Iterator<T> a,b;
    MergeIterators(Iterator<T> a, Iterator<T> b){
        this.a = a;
        this.b = b;
    }
    public boolean hasNext(){ return a.hasNext() || b.hasNext(); }
    // pre: there is a next
    public T next(){
        if (a.hasNext() )
            if (b.hasNext())
                if ( Math.random() < 0.5 )
                    return a.next();
                else
                    return b.next();
            else
                return a.next();
        else
           return b.next();
    }

    public void remove(){}
    
    public static void testMe(){
        List<String> a1 = Arrays.asList("Hans", "Lars", "Gurli", "Hedvig");
        List<String> a2 = Arrays.asList("Per", "Ib", "Odd", "Kim");
        MergeIterators<String> ms = new MergeIterators<String>(
            a1.iterator(), a2.iterator());
        while (ms.hasNext())
            System.out.println( ms.next());
        System.out.println("-----------");
    }
}