Abstraction (Corel Paradox and Java Cross Reference Guide)

General Info: Abstract Class / Abstract Member

An abstract class member is a member that is specified in a class but not implemented. Classes that inherit from the class will have to implement the abstract member. Abstract members are a technique for ensuring a common interface with descendant classes. An abstract class is a class you cannot instantiate. A pure abstract class is a class with only abstract members.

Languages Focus

Abstraction is supported at various levels with each language. A language could enforce abstraction at the class level (either enforcing a no-instantiation rule or a only abstract members rule), and with class members (member methods and/or properties).

Corel Paradox:   Not Supported	Java:   abstract Java supports marking a full class as abstract as well as class members. A subclass must either implement the abstract members or you must declare the subclass abstract (which delays the implementation to it's subclass). Syntax Example: public abstract class Dog {   abstract void Bark(); }  Java Abstraction (abstract)