Demo Observable Intersect of 2 lists.

ObservableIntersect.java

package com.charter.aesd.deviceactivation.edgeservice.rest;

import org.apache.commons.collections.CollectionUtils;
import rx.Observable;

import java.util.Collection;
import java.util.List;
import java.util.concurrent.TimeUnit;

import static java.util.Arrays.asList;

/**
 * Created by rhasija on 11/3/15.
 */
public class ObservableIntersect {

    public static void main(String[] args) {
        Observable<List<String>> o1 = Observable.interval(550, TimeUnit.MILLISECONDS).just(asList("a", "b", "c"));
        Observable<List<String>> o2 = Observable.interval(500, TimeUnit.MILLISECONDS).just(asList("a", "d", "c"));

        Observable.zip(o1, o2, (source, selected) -> {
            final Collection intersection = CollectionUtils.intersection(source, selected);
            final Collection collection = CollectionUtils.disjunction(selected, intersection);
            intersection.addAll(collection);
            System.out.println(intersection);
            return intersection;
        }).toBlocking().single();
    }
}