The problem is the following. Given a class GenericConfig which encapsulates a Map<String, Object> to contain several configurations, a class SpecificConfig is desired to have getters to retrieve specific map values.
For example, I want to avoid testing that GenericConfig.getProperties().get(KEY_OF_PROPERTY); is null and getting the value, with the burden of memorizing the key value in the calling method. I want to create a SpecificConfig that is created only if the key is present and that has a getProperty() method.
Example of what I want to avoid:
private final static String KEY_OF_PROPERTY = "key.for.my.value";
public void process(List<GenericConfig> configs) {
for(GenericConfig config: configs) {
String value = config.getProperties().get(KEY_OF_PROPERTY);
if (value != null) {
// do something
}
}
}
This is my attempt:
public final class SpecificConfig extends GenericConfig {
public SpecificConfig(GenericConfig from) {
if(from.getProperties().get(KEY_OF_PROPERTY) != null) {
this.properties = from.getProperties();
} else {
throw new ThisIsNotTheConfigIWant();
}
}
public String getProperty() {
return (String) this.properties.get(KEY_OF_PROPERTY);
}
}
So I can do the following:
public void process(List<GenericConfig> configs) {
for(GenericConfig config: configs) {
try {
SpecificConfig c = new SpecificConfig(config);
// now i can be sure that c is of the required type
// do stuff related to that type
} catch (ThisIsNotTheConfigIWant) { /* ignore this config */ }
}
}
Is throwing a checked exception in the constructor a bad thing in OOP? Does a pattern to solve this problem exist? Is it viable to instantiate null in the constructor instead of throwing an exception.
When calling the constructor it must return an instance of the class, never null. But if you want it to be possible to be null, use a static factory method instead:
public SpecificConfig maybeCreateFrom(GenericConfig c) {
if (<matches>) {
return SpecificConfig(c);
} else {
return null;
}
}
Then on the for-loop you can check for not-null. I think that is generally better than using clunky exceptions for control-flow handling. Though I suspect this is still not the best architecture for you.
Does the class GenericConfig holds a single config or a Map of configs? I would consider just creating methods to fetch configs with the existing keys + doing any null checks. Then you can just call getConfigX() or something.
I am working on a Spring Boot application and I have the following doubt.
I have this service method (that works fine) that insert an object into the DB calling the repository:
#Override
#Transactional
public CoinDTO createCoin(CoinDTO coin) throws DuplicateException {
Coin checkCoinExists = coinRepository.findByCode(coin.getCode());
if (checkCoinExists != null) {
String MsgErr = String.format("Coin %s already registered in the system !!! "
+ "Impossible to use POST", coin.getCode());
log.warning(MsgErr);
throw new DuplicateException(MsgErr);
}
Coin result = coinRepository.save(conversionService.convert(coin,Coin.class));
return conversionService.convert(result,CoinDTO.class);
}
As you can see the save() methjod return the inserted Coin object (that is an Hibernate entity class mapping my table). The service method than convert this Coin object into the CoinDTO object in order to return the DTO object instead the entity instance. It works fine and it is the expected behavior.
Now I created this second service method that simply retrieve the list of all the Coin objects and must return the list of the related CoinDTO objects:
#Override
public List<CoinDTO> getCoinList() {
List<Coin> coinsList = this.coinRepository.findAll();
return null;
}
and here I have the following doubt: I think that I can implement thid ENTITY to DTO conversion behavior iterating on the coinsList element, converting each element of the list one by one and then adding it to a new List list. It should work
Exist some more modern and smarter way to do it? Maybe using lambda function? Can you help me to implement this behavior in a modern and a smart way?
You may create an generic abstract class like this:
public abstract class AbstractConverter<T, DTO> {
public abstract T fromDto(DTO dto);
public abstract DTO toDTO(T t);
public List<T> fromDTOs(List<DTO> dtos) {
if (dtos == null || dtos.isEmpty()) {
return null;
} else {
return dtos.stream().map(this::fromDTO).collect(Collectors.toList());
}
}
public List<DTO> toDTOs(List<T> ts) {
if (ts == null || ts.isEmpty()) {
return null;
} else {
return ts.stream().map(this::toDTO).collect(Collectors.toList());
}
}
}
Then create another class that implements the aforecreated abstract class by assigning your desired values like this:
#Component(value = "coinConverter")
public class CoinConverter extends AbstractConverter<Coin, CoinDTO> {
#Override
public Coin fromDTO(CoinDTO dto) {
if (dto == null) {
return null;
} else {
Coin coin = new Coin();
// Assign all values you wanted to consume
// of the following form
// coin.setYourAttribite(dto.getYourAttribute())
return coin;
}
}
#Override
public CoinDTO toDTO(Coin coin) {
if (t == null) {
return null;
} else {
CoinDTO coinDTO = new CoinDTO();
// Assign all values you wanted to expose
// of the following form
// coinDTO.setYourAttribite(coin.getYourAttribute())
return coinDTO;
}
}
}
In controller layer you may change your existing code by this one:
#Autowired
#Qualifier("coinConverter")
AbstractConverter<Coin, CoinDTO> abstractConverter;
#Override
public List<CoinDTO> getCoinList() {
List<Coin> coinsList = this.coinRepository.findAll();
return abstractConverter.toDTOs(cointList);
}
This way your code is flexible to add more converters without changing the existing ones.
As far as I understand, you are looking for a way that makes the conversion process shorter and more convenient. if so use ModelMapper class in this case, read this http://modelmapper.org/ documentation, ModelMapper uses TypeTokens to allow mapping of generic parameterized types.
Not sure if I understood your question, but is the following what you are looking for:
#Override
public List<CoinDTO> getCoinList() {
return this.coinRepository.findAll().stream()
.map(coin -> conversionService.convert(coin, CoinDTO.class))
.collect(Collectors.toList());
}
I'm currently making some validations in my code and one of the main problem is I have a object list that has another object list and so on.
public class BigObject{
private Long idObject;
private String idLanguage;
private Date dateGeneration;
private List<FirstObject> firstObject;
//getters and setters
}
public class FirstObject{
private List<SecondObject> secondObject;
//getters and setters
}
public class SecondObject{
private Long order;
private String titol;
private int floatProperty;
//getters and setters
}
These are my classes and their are inside of another. I set up my Validator in the Main and created their respective class, now, in the validator class I have this:
public class BigObjectValidator implements Validator {
#Override
public boolean supports(Class clazz) {
return BigObject.class.equals(clazz)
|| FirstObject.class.equals(clazz)
|| SecondObject.class.equals(clazz);
}
#Override
public void validate(Object obj, Errors e) {
BigObject bigObject = (BigObject) obj;
ValidationUtils.rejectIfEmptyOrWhitespace(e, "idObject", "empty.id");
ValidationUtils.rejectIfEmptyOrWhitespace(e, "idLanguage", "empty.id");
ValidationUtils.rejectIfEmptyOrWhitespace(e, "dateGeneration", "empty.id");
if (!(bigObject.getFirstObject().isEmpty())) {
for (FirstObject firstObject : bigObject.getFirstObject()) {
if (firstObject.getSecondObject() != null) {
for (SecondObject secondObject : firstObject.getSecondObject()) {
if (secondObject != null){
validateSecondObject(secondObject,e);
}
}
}
}
}
}
private void validateSecondObject(SecondObject secondObject, Errors e) {
ValidationUtils.rejectIfEmptyOrWhitespace(e, "order", "order.empty");
ValidationUtils.rejectIfEmptyOrWhitespace(e, "titol", "order.empty");
ValidationUtils.rejectIfEmptyOrWhitespace(e, "floatProperty", "order.empty");
}
}
The main problem is I'm getting a org.springframework.beans.NotReadablePropertyException: Invalid property 'order' of bean class I'm trying to guess why is that, its because the validator is set up in the BigObject class and not the other ones. Now I don't know if I have to create another class inside BigObjectValidator or something like that.
Edit:
Main
try{
BigObject object = new BigObject();
List<FirstObject> firstObj = ArrayList<FirstObject>;
SecondObject secondObj = new SecondObject();
object.getIdObject("something");
object.getIdLanguage("En");
object.getDateGeneration("05-18-2018");
secondObject.setOrder(null);
firstObj.set(1,secondObject);
BeanPropertyBindingResult result = new BeanPropertyBindingResult(je.getValue(), "Object");
BigObjectValidator validateObject = new BigObjectValidator();
validateObject.validate(object, result);
if (result.hasErrors()){
System.out.println(result.getAllErrors().toString());
}
}catch(Exception e){
System.out.println(e);
}
Please look here
https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/validation/Errors.html
public interface Errors Stores and exposes information about
data-binding and validation errors for a specific object. Field names
can be properties of the target object (e.g. "name" when binding to a
customer object), or nested fields in case of subobjects (e.g.
"address.street"). Supports subtree navigation via
setNestedPath(String): for example, an AddressValidator validates
"address", not being aware that this is a subobject of customer.
If you pass the same Errors object to your validateSecondObject method, it still references the original obj, not your firstObject.. You must validate this differently. Either get a new instance of Errors (eg. org.springframework.validation.BindException) or do it by manually throwing exceptions
Caller:
switch (type){
case "creature":
Creature returnActor2 = getNextCreature();
boolean isEat2 = actOnNearby(getRightChromosome(Config.HardCode.creature), returnActor2.getLocation());
if (isEat2) {
actOnCreature(returnActor2);
}
break;
case "monster":
Monster returnActor3 = getNextMonster();
boolean isEat3 = actOnNearby(getRightChromosome(Config.HardCode.monster), returnActor3.getLocation());
if (isEat3) {
actOnMonster(returnActor3);
}
break;
}
It will call the following 2 methods:
private Monster getNextMonster() {
ArrayList<Actor> nearbyActors = getActors();
Monster mine = new Monster();
for (Actor a : nearbyActors) {
if (a instanceof Monster) {
mine = (Monster) a;
}
}
return mine;
}
private Creature getNextCreature() {
ArrayList<Actor> nearbyActors = getActors();
Creature mine = new Creature();
for (Actor a : nearbyActors) {
if (a instanceof Creature) {
mine = (Creature) a;
}
}
return mine;
}
The question
As you can see, the getNextXXXXX() method are pretty the same, just return different object, the logic is same, how to DRY? the actOnXXXX() seems falls in the DRY category as well, but it all about the same, use same logic against different object. How to solve this?
Make it accept a classtype:
private <T> T getNext(Class<T> type) {
for (Actor a : getActors()) {
if (type.isAssignableFrom(a.getClass())) {
return (T) a;
}
}
return null; //or type.newInstance(); if you want a guaranteed object, but this restricts your constructor.
}
Or with Java 8:
private <T> T getNext(Class<T> type) {
return (T) getActors().stream()
.filter(a -> type.isAssignableFrom(a.getClass()))
.findFirst().orElse(null);
}
But the usage is the same:
Monster next = getNext(Monster.class);
Breaking down the problem, you know two categories of things:
What you need:
A next object of t type.
A way of determining if an object is t
type
What you have:
The type t you want
A collection of objects, one of which might be t type
A new object via a no-args constructor (or null) if none are there
Additionally, the only variance between all these methods is one thing: Which type it is. So we literally "make that a variable", and as such it becomes a method parameter.
Breaking this down we simply need to organize the code in a manner which accomplishes this:
method: //receives a "type" as a parameter
iterate the list of possible `t`s //our list of objects
if some_t == type //our comparison, previously `a instanceof Type`
return some_t //our result is found
return null //or a new object, but essentially our "default"
The only primary differences here were:
Replacing some_t instanceof Type with type.isAssignableFrom(some_t.getClass())
Reason being here that this is simply how you determine this when using Class<T>
Our default can either be null or a new object
Making the object dynamically via reflection restricts your options and has exceptions to deal with. Returning null or an empty Optional<T> would help signify that you did not have a result, and the caller can act accordingly. You could potentially also just pass the default object itself, and then go back to the instanceof check.
Asking yourself this same hypothesis of "what do I need, and what can I provide/have", will help you map out breaking down the problem into smaller steps, and solving the larger puzzle.
I think, there is a confusion in your code and logic.
FOr example, if you need to iterate on list, you dont need to create a new object. That is, in the following code snippet, "new Monster()" doesn't need to be written
Monster mine = null; // new Monster();
for (Actor a : nearbyActors) {
if (a instanceof Monster) {
mine = (Monster) a;
}
}
Anyway, the answer is the "Type Inference in Java."
https://docs.oracle.com/javase/tutorial/java/generics/genTypeInference.html
The answer to your question is
package __TypeInference;
import java.util.ArrayList;
import java.util.List;
public class Main {
public static void main(String[] args) {
new Main().doLogic();
}
private void doLogic() {
List<Actor> nearbyActors = getActors();
for (Actor actor : nearbyActors) {
// do with the next actor
System.out.println(actor.toString());
}
}
private List<Actor> getActors() {
List<Actor> actors = new ArrayList<Actor>();
actors.add(new Monster());
actors.add(new Creature());
actors.add(new Monster());
actors.add(new Creature());
return actors;
}
class Monster extends Actor {
#Override
public String toString() {
return "Monster";
}
}
class Creature extends Actor {
#Override
public String toString() {
return "Creatue";
}
}
class Actor {
}
}
I think what you want is to combine getNextMonster and getNextCreature because they have repeated code.
The best thing to do here is to write a generic method that does this:
private <T extends Actor> T getNextActor(T newActor) {
ArrayList<Actor> nearbyActors = getActors();
T mine = newActor;
for (Actor a : nearbyActors) {
if (a instanceof T) {
mine = (T) a;
}
}
return mine;
}
And you can call it like this:
// This is equivalent to calling getNextCreature()
getNextActor(new Creature());
// This is equivalent to calling getNextMonster()
getNextActor(new Monster());
Let me explain the code.
The new method returns a type of Actor. You tell it what kind of actor you want by passing the argument. The argument is necessary because you cannot just initialize a generic type argument like this:
new T();
Because the parameterless constructor might not be available. So that's the job of the caller.
I don't really know what I'm talking about...
This method has the following advantages:
It reduces repeated code
It is flexible - when you want to add another method called getNextXXX (where XXX is a subclass of Actor), you don't need to. Just call getNextActor(new XXX())!
It increases maintainability - if you want to change the implementation of getNextXXX, you can just change one method instead of 2.
I need to compare dozens of fields in two objects (instances of the same class), and do some logging and updating in case there are differences. Meta code could look something like this:
if (a.getfield1 != b.getfield1)
log(a.getfield1 is different than b.getfield1)
b.field1 = a.field1
if (a.getfield2!= b.getfield2)
log(a.getfield2 is different than b.getfield2)
b.field2 = a.field2
...
if (a.getfieldn!= b.getfieldn)
log(a.getfieldn is different than b.getfieldn)
b.fieldn = a.fieldn
The code with all the comparisons is very terse, and I would like to somehow make it more compact. It would be nice if I could have a method which would take as a parameter method calls to setter and getter, and call this for all fields, but unfortunately this is not possible with java.
I have come up with three options, each which their own drawbacks.
1. Use reflection API to find out getters and setters
Ugly and could cause run time errors in case names of fields change
2. Change fields to public and manipulate them directly without using getters and setters
Ugly as well and would expose implementation of the class to external world
3. Have the containing class (entity) do the comparison, update changed fields and return log message
Entity should not take part in business logic
All fields are String type, and I can modify code of the class owning the fields if required.
EDIT: There are some fields in the class which must not be compared.
Use Annotations.
If you mark the fields that you need to compare (no matter if they are private, you still don't lose the encapsulation, and then get those fields and compare them. It could be as follows:
In the Class that need to be compared:
#ComparableField
private String field1;
#ComparableField
private String field2;
private String field_nocomparable;
And in the external class:
public <T> void compare(T t, T t2) throws IllegalArgumentException,
IllegalAccessException {
Field[] fields = t.getClass().getDeclaredFields();
if (fields != null) {
for (Field field : fields) {
if (field.isAnnotationPresent(ComparableField.class)) {
field.setAccessible(true);
if ( (field.get(t)).equals(field.get(t2)) )
System.out.println("equals");
field.setAccessible(false);
}
}
}
}
The code is not tested, but let me know if helps.
The JavaBeans API is intended to help with introspection. It has been around in one form or another since Java version 1.2 and has been pretty usable since version 1.4.
Demo code that compares a list of properties in two beans:
public static void compareBeans(PrintStream log,
Object bean1, Object bean2, String... propertyNames)
throws IntrospectionException,
IllegalAccessException, InvocationTargetException {
Set<String> names = new HashSet<String>(Arrays
.asList(propertyNames));
BeanInfo beanInfo = Introspector.getBeanInfo(bean1
.getClass());
for (PropertyDescriptor prop : beanInfo
.getPropertyDescriptors()) {
if (names.remove(prop.getName())) {
Method getter = prop.getReadMethod();
Object value1 = getter.invoke(bean1);
Object value2 = getter.invoke(bean2);
if (value1 == value2
|| (value1 != null && value1.equals(value2))) {
continue;
}
log.format("%s: %s is different than %s%n", prop
.getName(), "" + value1, "" + value2);
Method setter = prop.getWriteMethod();
setter.invoke(bean2, value2);
}
}
if (names.size() > 0) {
throw new IllegalArgumentException("" + names);
}
}
Sample invocation:
compareBeans(System.out, bean1, bean2, "foo", "bar");
If you go the annotations route, consider dumping reflection and generating the comparison code with a compile-time annotation processor or some other code generator.
I would go for option 1, but I would use getClass().getDeclaredFields() to access the fields instead of using the names.
public void compareAndUpdate(MyClass other) throws IllegalAccessException {
for (Field field : getClass().getDeclaredFields()) {
if (field.getType() == String.class) {
Object thisValue = field.get(this);
Object otherValue = field.get(other);
// if necessary check for null
if (!thisValue.equals(otherValue)) {
log(field.getName() + ": " + thisValue + " <> " + otherValue);
field.set(other, thisValue);
}
}
}
}
There are some restrictions here (if I'm right):
The compare method has to be implemented in the same class (in my opinion it should - regardless of its implementation) not in an external one.
Just the fields from this class are used, not the one's from a superclass.
Handling of IllegalAccessException necessary (I just throw it in the example above).
This is probably not too nice either, but it's far less evil (IMHO) than either of the two alternatives you've proposed.
How about providing a single getter/setter pair that takes a numeric index field and then have getter/setter dereference the index field to the relevant member variable?
i.e.:
public class MyClass {
public void setMember(int index, String value) {
switch (index) {
...
}
}
public String getMember(int index) {
...
}
static public String getMemberName(int index) {
...
}
}
And then in your external class:
public void compareAndUpdate(MyClass a, MyClass b) {
for (int i = 0; i < a.getMemberCount(); ++i) {
String sa = a.getMember();
String sb = b.getMember();
if (!sa.equals(sb)) {
Log.v("compare", a.getMemberName(i));
b.setMember(i, sa);
}
}
}
This at least allows you to keep all of the important logic in the class that's being examined.
While option 1 may be ugly, it will get the job done. Option 2 is even uglier, and opens your code to vulnerabilities you can't imagine. Even if you eventually rule out option 1, I pray you keep your existing code and not go for option 2.
Having said this, you can use reflection to get a list of the field names of the class, if you don't want to pass this as a static list to the method. Assuming you want to compare all fields, you can then dynamically create the comparisons, in a loop.
If this isn't the case, and the strings you compare are only some of the fields, you can examine the fields further and isolate only those that are of type String, and then proceed to compare.
Hope this helps,
Yuval =8-)
since
All fields are String type, and I can modify code of the class owning the fields if required.
you could try this class:
public class BigEntity {
private final Map<String, String> data;
public LongEntity() {
data = new HashMap<String, String>();
}
public String getFIELD1() {
return data.get(FIELD1);
}
public String getFIELD2() {
return data.get(FIELD2);
}
/* blah blah */
public void cloneAndLogDiffs(BigEntity other) {
for (String field : fields) {
String a = this.get(field);
String b = other.get(field);
if (!a.equals(b)) {
System.out.println("diff " + field);
other.set(field, this.get(field));
}
}
}
private String get(String field) {
String value = data.get(field);
if (value == null) {
value = "";
}
return value;
}
private void set(String field, String value) {
data.put(field, value);
}
#Override
public String toString() {
return data.toString();
}
magic code:
private static final String FIELD1 = "field1";
private static final String FIELD2 = "field2";
private static final String FIELD3 = "field3";
private static final String FIELD4 = "field4";
private static final String FIELDN = "fieldN";
private static final List<String> fields;
static {
fields = new LinkedList<String>();
for (Field field : LongEntity.class.getDeclaredFields()) {
if (field.getType() != String.class) {
continue;
}
if (!Modifier.isStatic(field.getModifiers())) {
continue;
}
fields.add(field.getName().toLowerCase());
}
}
this class has several advantages:
reflects once, at class loading
it is very simply adding new fields, just add new static field (a better solution here
is using Annotations: in the case you care using reflection works also java 1.4)
you could refactor this class in an abstract class, all derived class just get both
data and cloneAndLogDiffs()
the external interface is typesafe (you could also easily impose immutability)
no setAccessible calls: this method is problematic sometimes
A broad thought:
Create a new class whose object takes the following parameters: the first class to compare, the second class to compare, and a lists of getter & setter method names for the objects, where only methods of interest are included.
You can query with reflection the object's class, and from that its available methods. Assuming each getter method in the parameter list is included in the available methods for the class, you should be able to call the method to get the value for comparison.
Roughly sketched out something like (apologies if it isn't super-perfect... not my primary language):
public class MyComparator
{
//NOTE: Class a is the one that will get the value if different
//NOTE: getters and setters arrays must correspond exactly in this example
public static void CompareMyStuff(Object a, Object b, String[] getters, String[] setters)
{
Class a_class = a.getClass();
Class b_class = b.getClass();
//the GetNamesFrom... static methods are defined elsewhere in this class
String[] a_method_names = GetNamesFromMethods(a_class.getMethods());
String[] b_method_names = GetNamesFromMethods(b_class.getMethods());
String[] a_field_names = GetNamesFromFields(a_class.getFields());
//for relative brevity...
Class[] empty_class_arr = new Class[] {};
Object[] empty_obj_arr = new Object[] {};
for (int i = 0; i < getters.length; i++)
{
String getter_name = getter[i];
String setter_name = setter[i];
//NOTE: the ArrayContainsString static method defined elsewhere...
//ensure all matches up well...
if (ArrayContainsString(a_method_names, getter_name) &&
ArrayContainsString(b_method_names, getter_name) &&
ArrayContainsString(a_field_names, setter_name)
{
//get the values from the getter methods
String val_a = a_class.getMethod(getter_name, empty_class_arr).invoke(a, empty_obj_arr);
String val_b = b_class.getMethod(getter_name, empty_class_arr).invoke(b, empty_obj_arr);
if (val_a != val_b)
{
//LOG HERE
//set the value
a_class.getField(setter_name).set(a, val_b);
}
}
else
{
//do something here - bad names for getters and/or setters
}
}
}
}
You say you presently have getters and setters for all these fields? Okay, then change the underlying data from a bunch of individual fields to an array. Change all the getters and setters to access the array. I'd create constant tags for the indexes rather than using numbers for long-term maintainability. Also create a parallel array of flags indicating which fields should be processed. Then create a generic getter/setter pair that use an index, as well as a getter for the compare flag. Something like this:
public class SomeClass
{
final static int NUM_VALUES=3;
final static int FOO=0, BAR=1, PLUGH=2;
String[] values=new String[NUM_VALUES];
static boolean[] wantCompared={true, false, true};
public String getFoo()
{
return values[FOO];
}
public void setFoo(String foo)
{
values[FOO]=foo;
}
... etc ...
public int getValueCount()
{
return NUM_VALUES;
}
public String getValue(int x)
{
return values[x];
}
public void setValue(int x, String value)
{
values[x]=value;
}
public boolean getWantCompared(int x)
{
return wantCompared[x];
}
}
public class CompareClass
{
public void compare(SomeClass sc1, SomeClass sc2)
{
int z=sc1.getValueCount();
for (int x=0;x<z;++x)
{
if (!sc1.getWantCompared[x])
continue;
String sc1Value=sc1.getValue(x);
String sc2Value=sc2.getValue(x);
if (!sc1Value.equals(sc2Value)
{
writeLog(x, sc1Value, sc2Value);
sc2.setValue(x, sc1Value);
}
}
}
}
I just wrote this off the top of my head, I haven't tested it, so their may be bugs in the code, but I think the concept should work.
As you already have getters and setters, any other code using this class should continue to work unchanged. If there is no other code using this class, then throw away the existing getters and setters and just do everything with the array.
I would also propose a similar solution to the one by Alnitak.
If the fields need to be iterated when comparing, why not dispense with the separate fields, and put the data into an array, a HashMap or something similar that is appropriate.
Then you can access them programmatically, compare them etc. If different fields need to be treated & compared in different ways, you could create approriate helper classes for the values, which implement an interface.
Then you could just do
valueMap.get("myobject").compareAndChange(valueMap.get("myotherobject")
or something along those lines...