OOP Quotes 1: ADT vs Object

From: "On Understanding Data Abstraction, Revisited. William R. Cook"

 "in modern object-oriented languages, the issue boils down to whether or not classes are used as types. In a pure object-oriented style, classes are only used to construct objects, and interfaces are used for types. When classes are used as types, the programmer is implicitly choosing to use a form of abstract data type."

 

"To summarize, when a class name is used as a type, it represents an abstract data type"

 

"Object-Oriented Programming in Java

While Java is not a pure object-oriented language, it is possible to program in a pure object-oriented style by obeying the following rules

Classes only as constructors: A class name may only be used after the keyword new.

No primitive equality: The program must not use primitive equality (==). Primitive equality exposes representation and prevents simulation of one object by another. "

"Objects work with interfaces as types"

"OOP is using dynamic dispatch, ADT does not"

"ADT work with class as types"

Example ADT:

C++

class Person {}

Person p = new Person();

C

struct set rep; // representation is not defined in header  

typedef struct set rep* set;
set empty();
bool isEmpty(set s);

set insert(set s, int i); 

bool contains(set s, int i); 

set union(set s1, set s2);

 

 

Example Objects:

class PersonManager {};

 
class PersonSystem {

    void printName(Person p) {}

    PersonManager m_manager;

};

Person p = new Person();

PersonSystem.printName(p);