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How do I filter out a list of enums based on some criteria?

Say I have a class:
public enum Enums
{
// about thousand different Enums
}
and I have another class where a user signs in, and based on whether or not hes an admin or a regular user, the user has access to a limited list of enums. I know I can get the full list of all the enums from the class, but what is an elegant way to filter these by some criteria, without the Enums class knowing about user information?
Edit:
Here is a snip of what it looks like today:
#GET
#RolesAllowed({ADMIN})
#Path("/test")
public Response reply(#Auth User user)
{
JSONObject jsonObject = new JSONObject();
jsonObject.put("enums", Arrays.toString(Enums.values()));
return Response.ok(jsonObject.toJSONString()).build();
}
I am returning the full list of 1000+ events, when admin should only see a limited amount.

Let us take example of a week days name as enum. See below
public enum DaysOfWeekEnum {
SUNDAY("off"),
MONDAY("working"),
TUESDAY("working"),
WEDNESDAY("working"),
THURSDAY("working"),
FRIDAY("working"),
SATURDAY("off");
private String typeOfDay;
DaysOfWeekEnum(String typeOfDay) {
this.typeOfDay = typeOfDay;
}
// standard getters and setters
public static Stream<DaysOfWeekEnum> stream() {
return Stream.Of(DaysOfWeekEnum.values());
}
}
Now we will write an example in order to print the non-working days:
public class EnumStreamExample {
public static void main() {
DaysOfWeekEnum.stream()
.filter(d -> d.getTypeOfDay().equals("off"))
.forEach(System.out::println);
}
}
The output we get when we run this:
SUNDAY
SATURDAY
Sorry m on phone, please format code in answer.

Let us say your enum looks like
private enum Enums {
A,
B,
C,
D
}
where A, B are admin specific.
Create a class that allows access to the Enums based on whether the person is admin or not.
public class SO {
EnumSet<Enums> adminEnums = EnumSet.allOf(Enums.class);
EnumSet<Enums> nonAdminEnums = EnumSet.of(Enums.C, Enums.D);
public Set<Enums> getEnums(User user) {
boolean isAdmin = user.isAdmin(); //An example
return isAdmin ? adminEnums : nonAdminEnums;
}
An EnumSet is a special Set implementation optimized for storing a set of enums. adminEnums stores the list of all enums whereas nonAdminEnums has the limited set of enums.
You either have to explicitly specify the list of restricted enums for admin or specify the open enums and derive the other based on this. Not only this is tedious but error-prone. In the future, when you add a new enum instance, you have to update this too and it is easy to forget this.
It would be better if the enums itself contained this information like,
private enum Enums {
A(false),
B(false),
C(true),
D(true);
private boolean adminSpecific;
Enums(boolean adminSpecific) {
this.adminSpecific = adminSpecific;
}
public boolean isAdminSpecific() {
return adminSpecific;
}
}
In this case, we can derive the list based on the information contained in the enum instance.
Set<Enums> adminEnums = Arrays.stream(Enums.values())
.filter(Enums::isAdminSpecific)
.collect(Collectors.toSet());

accessing child constant in parent class in java

OK, so I have an interesting problem. I am using java/maven/spring-boot/cassandra... and I am trying to create a dynamic instantiation of the Mapper setup they use.
I.E.
//Users.java
import com.datastax.driver.mapping.annotations.Table;
#Table(keyspace="mykeyspace", name="users")
public class Users {
#PartitionKey
public UUID id;
//...
}
Now, in order to use this I would have to explicitly say ...
Users user = (DB).mapper(Users.class);
obviously replacing (DB) with my db class.
Which is a great model, but I am running into the problem of code repetition. My Cassandra database has 2 keyspaces, both keyspaces have the exact same tables with the exact same columns in the tables, (this is not my choice, this is an absolute must have according to my company). So when I need to access one or the other based on a form submission it becomes a mess of duplicated code, example:
//myWebController.java
import ...;
#RestController
public class MyRestController {
#RequestMapping(value="/orders", method=RequestMethod.POST)
public string getOrders(...) {
if(Objects.equals(client, "first_client_name") {
//do all the things to get first keyspace objects like....
FirstClientUsers users = (db).Mapper(FirstClientUsers.class);
//...
} else if(Objects.equals(client, "second_client_name") {
SecondClientUsers users = (db).Mapper(SecondClientUsers.class);
//....
}
return "";
}
I have been trying to use methods like...
Class cls = Class.forName(STRING_INPUT_VARIABLE_HERE);
and that works ok for base classes but when trying to use the Accessor stuff it no longer works because Accessors have to be interfaces, so when you do Class cls, it is no longer an interface.
I am trying to find any other solution on how to dynamically have this work and not have to have duplicate code for every possible client. Each client will have it's own namespace in Cassandra, with the exact same tables as all other ones.
I cannot change the database model, this is a must according to the company.
With PHP this is extremely simple since it doesn't care about typecasting as much, I can easily do...
function getData($name) {
$className = $name . 'Accessor';
$class = new $className();
}
and poof I have a dynamic class, but the problem I am running into is the Type specification where I have to explicitly say...
FirstClientUsers users = new FirstClientUsers();
//or even
FirstClientUsers users = Class.forName("FirstClientUsers");
I hope this is making sense, I can't imagine that I am the first person to have this problem, but I can't find any solutions online. So I am really hoping that someone knows how I can get this accomplished without duplicating the exact same logic for every single keyspace we have. It makes the code not maintainable and unnecessarily long.
Thank you in advance for any help you can offer.

Do not specify the keyspace in your model classes, and instead, use the so-called "session per keyspace" pattern.
Your model class would look like this (note that the keyspace is left undefined):
#Table(name = "users")
public class Users {
#PartitionKey
public UUID id;
//...
}
Your initialization code would have something like this:
Map<String, Mapper<Users>> mappers = new ConcurrentHashMap<String, Mapper<Users>>();
Cluster cluster = ...;
Session firstClientSession = cluster.connect("keyspace_first_client");
Session secondClientSession = cluster.connect("keyspace_second_client");
MappingManager firstClientManager = new MappingManager(firstClientSession);
MappingManager secondClientManager = new MappingManager(secondClientSession);
mappers.put("first_client", firstClientManager.mapper(Users.class));
mappers.put("second_client", secondClientManager.mapper(Users.class));
// etc. for all clients
You would then store the mappers object and make it available through dependency injection to other components in your application.
Finally, your REST service would look like this:
import ...
#RestController
public class MyRestController {
#javax.inject.Inject
private Map<String, Mapper<Users>> mappers;
#RequestMapping(value = "/orders", method = RequestMethod.POST)
public string getOrders(...) {
Mapper<Users> usersMapper = getUsersMapperForClient(client);
// process the request with the right client's mapper
}
private Mapper<Users> getUsersMapperForClient(String client) {
if (mappers.containsKey(client))
return mappers.get(client);
throw new RuntimeException("Unknown client: " + client);
}
}
Note how the mappers object is injected.
Small nit: I would name your class User in the singular instead of Users (in the plural).

How to use Spring jdbc templates (jdbcTemplate or namedParameterJDBCTem) to retrieve values from database

Few days into Spring now. Integrating Spring-JDBC into my web application. I was successfully able to preform CRUD operations on my DB, impressed with boiler-plate code reduction. But I am failing to use the query*() methods provided in NamedParameterJDBCTemplate. Most of the examples on the internet provide the usage of either RowMapper or ResultSetExtractor. Though both uses are fine, it forces me to create classes which have to implement these interfaces. I have to create bean for every type of data I am loading for the DB (or maybe I am mistaken).
Problem arises in code section where I have used something like this:
String query="select username, password from usertable where username=?"
ps=conn.prepareStatement(query);
ps.setString(username);
rs=ps.executeQuery();
if(rs.next()){
String username=rs.getString("username");
String password=rs.getString("password")
//Performs operation on them
}
As these values are not stored in any bean and used directly, I am not able to integrate jdbcTemplate in these kind of situations.
Another situation arises when I am extracting only part of properties present in bean from my database.
Example:
public class MangaBean{
private String author;
private String title;
private String isbn;
private String releaseDate;
private String rating;
//getters and setters
}
Mapper:
public class MangaBeanMapper implements RowMapper<MangaBean>{
#Override
public MangaBean mapRow(ResultSet rs, int arg1) throws SQLException {
MangaBean mb=new MangaBean();
mb.setAuthor(rs.getString("author"));
mb.setTitle(rs.getString("title"));
mb.setIsbn(rs.getString("isbn"));
mb.setReleaseDate(rs.getString("releaseDate"));
mb.setRating(rs.getString("rating"));
return mb;
}
}
The above arrangement runs fine like this:
String query="select * from manga_data where isbn=:isbn"
Map<String, String> paramMap=new HashMap<String, String>();
paramMap.put("isbn", someBean.getIsbn());
return template.query(query, paramMap, new MangaBeanMapper());
However, if I only want to retrieve two/three values from my db, I cannot use the above pattern as it generates a BadSqlGrammarException: releaseDate does not exist in ResultSet . Example :
String query="select title, author where isbn=:isbn"
Map<String, String> paramMap=new HashMap<String, String>();
paramMap.put("isbn", someBean.getIsbn());
return template.query(query, paramMap, new MangaBeanMapper());
Template is an instance of NamedParameterJDBCTemplate. Please advice me solutions for these situations.

The other answers are sensible: you should create a DTO bean, or use the BeanPropertyRowMapper.
But if you want to be able to have more control than the BeanPropertyRowMapper, (or reflection makes it too slow), you can use the
queryForMap
method, which will return you a list of Maps (one per row) with the returned columns as keys. Because you can call get(/* key that is not there */) on a Map without throwing an exception (it will just return null), you can use the same code to populate your object irrespective of which columns you selected.

You don't even need to write your own RowMapper, just use the BeanPropertyRowMapper that spring provides. The way it works is it matches the column names returned to the properties of your bean. Your query has columns that match your bean exactly, if it didn't you would use an as in your select as follows...
-- This query matches a property named matchingName in the bean
select my_column_that doesnt_match as matching_name from mytable;
The BeanPropertyRowMapper should work with both queries you listed.

Typically, yes : for most queries you would create a bean or object to transform the result into. I would suggest that more most cases, that's want you want to do.
However, you can create a RowMapper that maps a result set to a map, instead of a bean, like this. Downside would be be losing the type management of beans, and you'd be relying on your jdbc driver to return the correct type for each column.
As #NimChimpskey has just posted, it's best to create a tiny bean object : but if you really don't want to do that, this is another option.
class SimpleRowMapper implements RowMapper<Map<String, Object>> {
String[] columns;
SimpleRowMapper(String[] columns) {
this.columns = columns;
}
#Override
public Map<String, Object> mapRow(ResultSet resultSet, int i) throws SQLException {
Map<String, Object> rowAsMap = new HashMap<String, Object>();
for (String column : columns) {
rowAsMap.put(column, resultSet.getObject(column));
}
return rowAsMap;
}
}

In yr first example I would just create a DTO Bean/Value object to store them. There is a reason its a commonly implemented pattern, it takes minutes to code and provides many long term benefits.
In your second example, create a second implementation of rowmapper where you don;t set the fields, or supply a null/subsitute value to mangabean where necessary :
#Override
public MangaBean mapRow(ResultSet rs, int arg1) throws SQLException {
MangaBean mb=new MangaBean();
mb.setAuthor(rs.getString("author"));
mb.setTitle(rs.getString("title"));
/* mb.setIsbn("unknown");*/
mb.setReleaseDate("unknown");
mb.setRating(null);
return mb;
}

How do I add ArrayLists to an ArrayList?

So, I have already created an ArrayList<>, say Staff List.
private List<Staff> staffs = new ArrayList<Staff>();
public StaffFacade() {
staffs.add(new Staff("1", "James"));
staffs.add(new Staff("2", "Mike"));
staffs.add(new Staff("3", "Lina"));
staffs.add(new Staff("4", "John"));
}
public List<Staff> getStaffs() {
return staffs;
}
And I want to create another List that contains Staff List (by adding), so that I don't have to add the same Staff in StaffFacade?
I already created this BorrowFacade:
private List<Borrow> borrows = new ArrayList<Borrow>();
public BorrowFacade() {
borrows.add(new Borrow()) //How do I add this?
}
public List<Borrow> getBorrows() {
return borrows;
}
Referring to my question above, I don't know how to add new Staff List that has already been created.
This is the constructor for the Borrow List:
public Borrow(Date dueDate, Staff staff, Book books) {
this.dueDate = dueDate;
this.staff = staff;
this.books = books;
}
Of course, I put Date there because I wanted to add Date inside the List too.
MAJOR EDIT
Okay so let me try to put it this way. I have 4 classes which is StaffFacade, BorrowFacade, Borrow and Staff.
This is what I wrote inside StaffFacade:
public class StaffFacade {
private List<Staff> staffs = new ArrayList<Staff>();
public StaffFacade() {
staffs.add(new Staff("1", "James"));
staffs.add(new Staff("2", "Mike"));
staffs.add(new Staff("3", "Lina"));
staffs.add(new Staff("4", "John"));
}
public List<Staff> getStaffs() {
return staffs;
}
}
BorrowFacade:
public class BorrowFacade {
private List<Borrow> borrows = new ArrayList<Borrow>();
public BorrowFacade() {
borrows.add(staffsList);
}
public List<Borrow> getBorrows() {
return borrows;
}
}
Borrow (parts of it, the rest are just setters and getters)
public class Borrow {
String id;
Date dueDate;
Staff staff;
Book books;
public Borrow(String id, Date dueDate, Staff staff, Book books) {
this.id = id;
this.dueDate = dueDate;
this.staff = staff;
this.books = books;
}
Staff:
public class Staff{
String id, name;
public Staff(String id, String name) {
this.id = id;
this.name = name;
}
The problem is in BorrowFacade. I don't know how to add List that has been created in StaffFacade into BorrowFacade's List which is List<Borrow> borrows;
I'm very sorry for the confusion. If anything please ask me. I really want this program to work.

If you have a collection you can addAll(someOtherCollection); but I am not sure I fully understand your question: you refer to a 'constructor for the Borrow List' but you show a constructor for a Borrow class which is not a list.
You seem to be mixing up an instance of an individual class (e.g. Book) with a collection or plurality of that class: Book books (why is it plural? What are you trying to express?)
Edit:
Based on you comment, I think you're trying to understand how to construct the Borrow objects to be placed in the list.
The difference between constructed the Staff List is that you 'know' the staff ahead of time - albeit these are canned values.
The Borrow object seems to express a particular person borrowing a particular book due back on a certain date. If so, you need to have these details somewhere, for example from a database. The reason you're having trouble is you're trying to construct these objects in your Facade instead of just encapsulating ones that already exist.
public class Facade {
private List<Borrow> borrows = new ArrayList<Borrow>();
// Pass the items in to the constructor
public Facade(List<Borrow> borrows) {
this.borrows.addAll(borrows);
}
// You could call this externally in a loop to populate one by one
public void addBorrow(Borrow borrow) {
borrows.add(borrow);
}
}
To restate: your Staff and your Borrow objects have to come from somewhere, so if they're already in a collection, use addAll, if not, just iterate the list and call add. Don't construct the objects in your Facades.
Edit 2:
In response to your amended question, you can't do this. You're trying to add a list of a particulr object (Staff) in to a list of another type of object (Borrow). This is just inherently wrong. I don't quite know how else to say it. If you asked me to give you a List of my favourite Stack Overflow questions, would you expect to find my favourite Stack Overflow user in that list? This is the fundamental nature of type safety. Now, if you asked me to give you a list of my Favourite Things then it is perfectly reasonable to expect to find various types of things in there - Stack Overflow Questions, Wines, Foods, etc. because they would conceptually share a common Favourite parent class or interface.
To be frank, I think you neeed to (re-)read up on the basic nature of Java generics and type safety, but in pursuit of the almighty reputation, here goes:
Note: I'm using StaffMember and BorrowedItem as names here to try to illustrate the value of good naming conventions.
You seem to want a Facade class for reasons none of us understand. Okay, we can accept that. Your Facade class seems to contain a list of objects. You have created multiple classes to accomplish this, with no discernable difference between the two except which objects are listed inside. Generics to the rescue:
public class Facade<T> {
private List<T> list = new ArrayList<T>();
public Facade(List<T> existingList) {
list.addAll(existingList);
}
}
This facade holds a list of objects, meaning you can do this:
List<StaffMember> staffMembers= new ArrayList<StaffMember>();
// .. assume list is populated here
Facade<StaffMember> staffMembersFacade = new Facade<StaffMember>(staffMembers);
Likewise, with the same facade class:
List<BorrowedItem> borrowedItems = new ArrayList<BorrowedItem>();
// ... populate borrowed items
Facade<BorrowedItem> borrowedItemsFacade = new Facade<BorrowedItem<(borrowedItems);
But you aren't adding StaffMember objects to the borrowedItemsFacade. At least not directly - in your example a BorrowedItem has a Date and it also points to which StaffMember borrowed it.
So at this point you have two lists - a list of StaffMembers, and a list of BorrowedItems but you really have to ask yourself what purpose does this serve? Doesn't it make more sense for a single StaffMember to have a List<BorrowedItem> to keep track of all the items they borrowed?
class BorrowedItem {
Date dueDate;
StaffMember borrower;
}
class StaffMember {
String name;
List<BorrowedItem> borrowedItems;
}
Now this provides the opportunity to add a function to the StaffMember like this:
List<BorrowedItem> getOverdueItems() {
List<BorrowedItem> overdueItems = new ArrayList<BorrowedItem>();
Date today = getTodaysDate(); // Calendar.getInstance etc.
for (BorrowedItem borrowedItem : borrowedItems) {
Date dueDate = borrowedItem.getDueDate();
if (today.after(dueDate)) {
overdueItems.add(borrowedItem);
}
}
return overdueItems;
}
Do you see how you need to create meaningful relationships between these classes in order for there to be anything useful to happen?
Then you can add functions to let someone lend an item to another person, or take something from someone, etc.
So yeah, Collections.addAll is what you're looking for, I think.

Persistent data structures in Java

Does anyone know a library or some at least some research on creating and using persistent data structures in Java? I don't refer to persistence as long term storage but persistence in terms of immutability (see Wikipedia entry).
I'm currently exploring different ways to model an api for persistent structures. Using builders seems to be a interesting solution:
// create persistent instance
Person p = Builder.create(Person.class)
.withName("Joe")
.withAddress(Builder.create(Address.class)
.withCity("paris")
.build())
.build();
// change persistent instance, i.e. create a new one
Person p2 = Builder.update(p).withName("Jack");
Person p3 = Builder.update(p)
.withAddress(Builder.update(p.address())
.withCity("Berlin")
.build)
.build();
But this still feels somewhat boilerplated. Any ideas?

Builders will make your code too verbose to be usable. In practice, almost all immutable data structures I've seen pass in state through the constructor. For what its worth, here are a nice series of posts describing immutable data structures in C# (which should convert readily into Java):
Part 1: Kinds of Immutability
Part 2: Simple Immutable Stack
Part 3: Covariant Immutable Stack
Part 4: Immutable Queue
Part 5: Lolz! (included for completeness)
Part 6: Simple Binary Tree
Part 7: More on Binary Trees
Part 8: Even More on Binary Trees
Part 9: AVL Tree Implementation
Part 10: Double-ended Queue
Part 11: Working Double-ended Queue Implementation
C# and Java are extremely verbose, so the code in these articles is quite scary. I recommend learning OCaml, F#, or Scala and familiarizing yourself with immutability with those languages. Once you master the technique, you'll be able to apply the same coding style to Java much more easily.

I guess the obvious choices are:
o Switch to a transient data structure (builder) for the update. This is quite normal. StringBuilder for String manipulation for example. As your example.
Person p3 =
Builder.update(p)
.withAddress(
Builder.update(p.address())
.withCity("Berlin")
.build()
)
.build();
o Always use persistent structures. Although there appears to be lots of copying, you should actually be sharing almost all state, so it is nowhere near as bad as it looks.
final Person p3 = p
.withAddress(
p.address().withCity("Berlin")
);
o Explode the data structure into lots of variables and recombine with one huge and confusing constructor.
final Person p3 = Person.of(
p.name(),
Address.of(
p.house(), p.street(), "Berlin", p.country()
),
p.x(),
p.y(),
p.z()
);
o Use call back interfaces to provide the new data. Even more boilerplate.
final Person p3 = Person.of(new PersonInfo(
public String name () { return p.name(); )
public Address address() { return Address.of(new AddressInfo() {
private final Address a = p.address();
public String house () { return a.house() ; }
public String street () { return a.street() ; }
public String city () { return "Berlin" ; }
public String country() { return a.country(); }
})),
public Xxx x() { return p.x(); }
public Yyy y() { return p.y(); }
public Zzz z() { return p.z(); }
});
o Use nasty hacks to make fields transiently available to code.
final Person p3 = new PersonExploder(p) {{
a = new AddressExploder(a) {{
city = "Berlin";
}}.get();
}}.get();
(Funnily enough I was just put down a copy of Purely Functional Data Structures by Chris Okasaki.)

Have a look at Functional Java. Currently provided persistent datastructures include:
Singly-linked list (fj.data.List)
Lazy singly-linked list (fj.data.Stream)
Nonempty list (fj.data.NonEmptyList)
Optional value (a container of length 0 or 1) (fj.data.Option)
Set (fj.data.Set)
Multi-way tree (a.k.a. rose tree) (fj.data.Tree)
Immutable map (fj.data.TreeMap)
Products (tuples) of arity 1-8 (fj.P1..P8)
Vectors of arity 2-8 (fj.data.vector.V2..V8)
Pointed list (fj.data.Zipper)
Pointed tree (fj.data.TreeZipper)
Type-safe, generic heterogeneous list (fj.data.hlist.HList)
Immutable arrays (fj.data.Array)
Disjoint union datatype (fj.data.Either)
A number of usage examples are provided with the binary distribution. The source is available under a BSD license from Google Code.

I implemented a few persistent data structures in Java. All open source (GPL) on Google code for anyone who is interested:
http://code.google.com/p/mikeralib/source/browse/#svn/trunk/Mikera/src/mikera/persistent
The main ones I have so far are:
Persistent mutable test object
Persistent hash maps
Persistent vectors/lists
Persistent sets (including a specialised persistent set of ints)

Follow a very simple tentative with dynamic proxy:
class ImmutableBuilder {
static <T> T of(Immutable immutable) {
Class<?> targetClass = immutable.getTargetClass();
return (T) Proxy.newProxyInstance(targetClass.getClassLoader(),
new Class<?>[]{targetClass},
immutable);
}
public static <T> T of(Class<T> aClass) {
return of(new Immutable(aClass, new HashMap<String, Object>()));
}
}
class Immutable implements InvocationHandler {
private final Class<?> targetClass;
private final Map<String, Object> fields;
public Immutable(Class<?> aTargetClass, Map<String, Object> immutableFields) {
targetClass = aTargetClass;
fields = immutableFields;
}
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if (method.getName().equals("toString")) {
// XXX: toString() result can be cached
return fields.toString();
}
if (method.getName().equals("hashCode")) {
// XXX: hashCode() result can be cached
return fields.hashCode();
}
// XXX: naming policy here
String fieldName = method.getName();
if (method.getReturnType().equals(targetClass)) {
Map<String, Object> newFields = new HashMap<String, Object>(fields);
newFields.put(fieldName, args[0]);
return ImmutableBuilder.of(new Immutable(targetClass, newFields));
} else {
return fields.get(fieldName);
}
}
public Class<?> getTargetClass() {
return targetClass;
}
}
usage:
interface Person {
String name();
Person name(String name);
int age();
Person age(int age);
}
public class Main {
public static void main(String[] args) {
Person mark = ImmutableBuilder.of(Person.class).name("mark").age(32);
Person john = mark.name("john").age(24);
System.out.println(mark);
System.out.println(john);
}
}
grow directions:
naming policy (getName, withName, name)
caching toString(), hashCode()
equals() implementations should be straightforward (although not implemented)
hope it helps :)

It is very difficult, if not impossible, to make things immutable that ain't designed so.
If you can design from ground up:
use only final fields
do not reference non immutable objects

Do you want immutability :
so external code cannot change the data?
so once set a value cannot be changed?
In both cases there are easier ways to accomplish the desired result.
Stopping external code from changing the data is easy with interfaces:
public interface Person {
String getName();
Address getAddress();
}
public interface PersonImplementor extends Person {
void setName(String name);
void setAddress(Address address);
}
public interface Address {
String getCity();
}
public interface AddressImplementor {
void setCity(String city);
}
Then to stop changes to a value once set is also "easy" using java.util.concurrent.atomic.AtomicReference (although hibernate or some other persistence layer usage may need to be modified):
class PersonImpl implements PersonImplementor {
private AtomicReference<String> name;
private AtomicReference<Address> address;
public void setName(String name) {
if ( !this.name.compareAndSet(name, name)
&& !this.name.compareAndSet(null, name)) {
throw new IllegalStateException("name already set to "+this.name.get()+" cannot set to "+name);
}
}
// .. similar code follows....
}
But why do you need anything more than just interfaces to accomplish the task?

Google Guava now hosts a variety of immutable/persistent data structures.