java version

gistfile1.java

class Person {
	private String firstName;
	private String lastName;
	private Address address;
	public Person() {
	}
	public Person(String firstName, String lastName, Address address) {
		this.firstName = firstName;
		this.lastName = lastName;
		this.address = address;
	}
	public String getFirstName() {
		return firstName;
	}
	public String getLastName() {
		return lastName;
	}
	public String getAddress() {
		return address;
	}
	public String setFirstName(String firstName) {
		this.firstName = firstName;
	}
	public String setLastName(String lastName) {
		this.lastName = lastName;
	}
	public String setAddress(Address address) {
		this.address = address;
	}
}

class Address {
	private String city;
	private String street;
	...
	public Address() {
	}
	public Address(String city, String street) {
		this.city = city;
		this.street = street;
	}

	public String getCity() {
		return city;
	}
	public String setCity(String city) {
		this.city = city;
	}
	public String getStreet() {
		return ...;
	}
	public String setStreet(String street) {
		this.... = ...
	}
	...

}


...
List<Persons> persons = getAListSomewhere();
List<Persons> filtered = doFilter(persons, new Filter<Person>() {
	public boolean filter(Person p) {
		return p.getAddress().getCity().equals("Kyiv");
	}
});

List<T> doFilter(List<T> list, Filter<T> filter) {
	List<T> result = new ArrayList<T>(list.size());
	for (T t : list) {
		if (filter(t)) {
			result.add(t);
		}
	}
	return result;
}

Set<Address> extractedAddresses = doExtract(list, new Extractor<Person,Address>() {
	public Address extract(Person p) {
		return p.address;
	}
})

List<Out> doExtract<In,Out>(List<In> list, Extractor<In,Out> extractor) {
	...
	for (In x : list) {
		...
	}
	...
}