crea

Creation and Initialization

Many OOP languages ( Smalltalk, C++,Java, objective-C) tie together object creation and initialization.

Avoids creating an object without properly initializing its fields
Avoid creating an object and initializing its fields more than once

We discuss two mechanisms, classes(factory) methods and constructors.

Class Methods

smalltalk and object Pascal use "object creators" to initialize objects at creation

Object creators associated with class as whole, not an instance

id aCard;

aCard = [ Card rank:2 suit: 3 ];

Constructors in java

As in ++, a Constructor in java is a method ( i.e. member function)

has same name as a class
can take argument lists., like function.
invoked implicitly by new, explicitly by this in other constructors

     class newClass {
                . . . . . . .
                newClass ( int i ) {

                    . . . // initialization

                        }
}

Destructors in java

Garbage collection recovers memory no longer referenced
method finalize ( ) ,if defined, called when reclaiming memory for object

          - Does any other "housecleaning" needed (close files, etc.)
          - Executes at unpredictable time
          - Should not be depended upon for correctness - do critical ' housecleaning" tasks explicitly