How to group elements of a List by elements of another in Java 8

Question

I have the following problem: Given these classes,

class Person {
    private String zip;
    ...
    public String getZip(){
        return zip;
    }
}

class          


        

Answer 1

I suspect the cleanest way to do this -- I'm not quite happy with the other answers posted -- would be

 persons.stream().collect(Collectors.toMap(
    person -> person,
    person -> regions.stream()
       .filter(region -> region.getZipCodes().contains(person.getZip()))
       .collect(Collectors.toList())));