Q: The UJO Framework offers several Ujo implementations. What is the best implementation?
A: I think that implementation QuickUjo satisfies both requirements for good performance and user friendliness.

Q: How to use the QuickUjo for my business object ?
A: Follow the next code. The static block with init(..) method assigns correct indexes and names into Property objects.

public class Person extends QuickUjo {
  public static final Property<Person,String > NAME = newProperty(String.class);
  public static final Property<Person,Boolean> MALE = newProperty(Boolean.class);
  public static final Property<Person,Double > CASH = newProperty(0);
  static { init(Person.class); }
}

Q: Is the static block calling the QuickUjo.init(..) method necessary?
A: The static block with init(..) method assigns correct indexes and names into Property objects. Alternatively you can call the method Ujo.readProperties() before the first using of the object instead of.

Q: Why a subclass OrmTable implementations don't use the static block init(..)?
A: The Ujorm initializes all properties automatically in the ORM meta-model building time.

Q: May the UjoProperty contain a reference to a List?
A: Yes, of course, however a better solution is to use a special subtype ListProperty.

public class Person extends QuickUjo {
  public static final ListProperty<Person,String > EMAILS = newListProperty("email", String.class);
  static { init(Person.class); }
}

Q: How do I quickly copy all the attributes of an UJO object to another instance?
A: Use the next code:

Person from = getPerson();
Person to = new Person ();
for (UjoProperty p : newUser.readProperties()) {
    p.copy(from, to);
}

Q: How do I copy all the attributes of an UJO object to another instance excluding a property?
A: See the next code for excluding a CASH property for example. Note that each property have got a unique instance of the object so it is allowed to use the == operator to a quick comparison:

for (UjoProperty p : oldUser.readProperties()) {
    if (Person.CASH != p) {
        newUser.writeValue(p, oldUser.readValue(p));
    }
}

Q: How to test that a type of property is the Date for example?
A: Use a property method isTypeOf(Class)

if (property.isTypeOf(Date.class)) {
    // your code ...
}

Q: How to save the UJO from to a XML file?
A: Use the next code:

String defaultXmlHeader = null;
UjoManagerXML.getInstance().saveXML(dataFile, person, defaultXmlHeader, "Save");

Q: How to restore the UJO from a XML file?
A: Use the next code:

Person user = UjoManagerXML.getInstance().parseXML(dataFile, Person.class, "Restore");

Q: How works the QuickUjo implementation?
A: The one QuickUjo instance have got the exactly one field: private array of objects. Because each instance of UjoProperty has an index to the one cell of the array, so it is easy to read or write values.

Q: How to use parentheses on composed Criterions?
A: A Criterion instance composed from aother criterions works as an expression separated by parentheses. See the next example:

// Consider instances:
 Criterion<Person> a, b, c, result;
 a = Criterion.where(CASH, Operator.GT, 10.0);
 b = Criterion.where(CASH, Operator.LE, 20.0);
 c = Criterion.where(NAME, Operator.STARTS, "P");
 
 // Expression 1: (a OR b) AND c :
 result = (a.or(b)).and(c); // or simply:
 result = a.or(b).and(c); 
 
 // Expression 2: a AND (b OR c) :
 result = a.and(b.or(c));