A Class is the definition of an object. It represents a concept within the architecture of the software system. A Class generally defines all the elements of an object but does not have any physical reality in the computing system (see Object).
The Object Constructor is a private method that actually creates an instance of the object by allocating memory and initializing all the data elements. Constructors can also accept a series of arguments (values) so that various forms or flavors of an object can be created.
A Data Member is part of the internal data elements defined by an object class. An object always defines its own data (which, of course, can be other objects).
A Design Pattern is part of the re-usable, conceptual framework in an object oriented system. Patterns reflect and define one of the many different ways in which data is processed, objects are created, destroyed, or manipulated, and information and control moves through an object oriented system. Large, complex object systems are built from the interconnection of design patterns.
Encapsulation is the process of hiding the internal workings of an object. A well defined and well behaved object only exposes its interface – that is, in most cases, the methods necessary to put data into and get data out of the object. Hiding the actual data elements, the algorithms, and the mechanics necessary to maintain the integrity and security of the object’s data keeps application software from depending on any particular implementation of the object and also insures that the client-to-object behavior is well understood and consistent.
Inheritance is the ability of one object to inherit properties of one or more parent objects. Inheritance is an important integrity, extensibility, and control mechanism in an object oriented system. Inheritance works in a tree structure, When B inherits from A, then B is a kind of A. Thus a Customer is A-Kind-Of Person. Inheritance allows system designers to establish stable controls and properties for a small, broad class of concepts and then build on these to populate a wider architecture of objects.
A Method is a procedure or operation associated with the object. The actual manipulation of data within an object (the definition of algorithms, error handling routines, and auditing as an example) as well as the published interface to the object (routines to put data into and get data out of an object) are all handled through a set of methods. TOP
An Object is the instance of a class. If CUSTOMER is a class, then (using the Java syntax)
CUSTOMER myCustomer = new CUSTOMER()
creates the corresponding object. This is also called an instance of the class. When the new operator is used, the associated object constructor is called and the class is allocated real memory. TOP
Polymorphism is the ability to change the syntax of the language in order to adapt existing language elements to new uses. As an example, associated arithmetic operators with matrix operators in a Matrix class. In this way the multiplication operator in C = A * B actually invokes a method that performs matrix multiplication or vector and matrix multiplication depending on the structure type of “A” and “B”. TOP
A Private method or data element is only visible within the object class itself, neither external objects, other software systems, nor inherited objects can see a private member. TOP
A Protected method or data element is private to the object and all its inherited objets. That is, Objects B and C that inherit from Object A also have access to all the protected data and method elements of A. TOP
A Public method or data element is visible to any user of the class. These elements comprise the public interface for the object and, for well behaved and well formed classes, are the only elements that can be used by application software to access and manipulate an object. TOP