ICS2602: Module 11 OOP

Object-Oriented Programming

is a computer programming model that organizes software design
around data, or objects, rather than functions and logic. An object can be defined as a data field that has unique attributes and behavior.

object

a software bundle of related state
and behavior. Software objects are often used to model the real-world objects that you find in everyday life

Parts of an OBJECT

Attributes and Methods

Benefits of Bundling Code into Individual Software Object

Modularity, Information-hiding, Code re-use, and Pluggability and Debugging Ease

Modularity

The source code for an object can be written and maintained
independently of the source code for other objects. Once created, an object can be easily passed around inside the system.

Information-hiding

By interacting only with an object's methods, the details of
its internal implementation remain hidden from the outside world

Code re-use

If an object already exists (perhaps written by another software
developer), you can use that object in your program. This allows specialists to implement/test/debug complex, task-specific objects, which you can then trust to run in your own code.

Pluggability and debugging ease

If a particular object turns out to be problematic, you can simply remove it from your application and plug in a different object as its replacement. This is analogous to fixing mechanical problems in the real world. If a bolt breaks, you replace it, not the entire machine.

class

blueprint or prototype from which objects
are created.

class

This section defines a class that models the state and behavior of a real-world object.

class

It intentionally focuses on the basics, showing how even a simple class can cleanly model state and behavior.

class diagram

depicts a static view of an application

class diagram

It represents the types of objects residing in the system and the relationships between them.

class diagram

A class consists of its objects, and also it may inherit from other classes.

class diagram

used to visualize, describe, document various different aspects of the system, and also construct executable software code.

Components of a Class Diagram

Upper, Middle, and Lower Section

Upper Section

encompasses the name of the class

class

a representation of similar objects that shares
the same relationships, attributes, operations,
and semantics

capitalize

? the initial letter of the class
name

center

Place the class name in the ? of the
upper section.

bold

(class diagram sections) A class name must be written in ? format.

italics

(class diagram sections) The name of the abstract class should be written in ? format

Middle Section

(class diagram sections) constitutes the attributes, which describe the quality of the class

symbol for PUBLIC in class diagram

+

symbol for PRIVATE in class diagram

-

symbol for PROTECTED in class diagram

#

symbol for PACKAGE in class diagram

~

true

The accessibility of an attribute class is
illustrated by the visibility factors.

true

A meaningful name should be assigned to
the attribute, which will explain its usage
inside the class.

Lower Section

(class diagram sections) contain methods or operations

Lower Section

(class diagram sections) The methods are represented in the form of a list, where each method is written in a single line.

Lower Section

(class diagram sections) It demonstrates how a class interacts with data.

Types of Relationships

Dependency, Generalization, Association, Multiplicity, Aggregation, and Composition

Dependency

(types of relationships) a semantic relationship between two or more classes where a change in one class cause changes in another class. In the following example, Student_Name is dependent on the Student_Id.

Dependency

(types of relationships) It forms a weaker relationship.

Generalization

(types of relationships) a relationship between a parent
class (superclass) and a child class (subclass). In this, the child class is inherited from the parent class.

For example, The Current Account, Saving Account, and Credit Account
are the generalized form of Bank Account.

Association

(types of relationships) It describes a static or physical connection between two or more objects. It depicts how many objects are there in the relationship.


For example, a department is associated with the college.

Multiplicity

(types of relationships) It defines a specific range of allowable instances of attributes. In case if a range is not specified, one is considered as a default multiplicity.

For example, multiple patients are admitted to one hospital.

Aggregation

(types of relationships) is a subset of association, which represents
has a relationship.

Aggregation

(types of relationships) It is more specific than association. It defines a part-whole or part-of relationship.

Aggregation

(types of relationships) In this kind of relationship, the child class can exist independently of its parent class. The company encompasses a number of employees, and even if one employee resigns, the company still exists.

Composition

(types of relationships) is a subset of aggregation.

Composition

(types of relationships) It portrays the dependency between the parent and its child, which means if one part is deleted, then the other part also gets discarded. It represents a whole-part relationship.

A contact book consists of multiple contacts, and if you delete the contact book, all the contacts will be lost.

true

In the abstract class, no objects can be a direct entity of
the abstract class.

abstract class

can neither be declared nor be instantiated

abstract class

used to find the functionalities across the classes

The notation of the abstract class is similar to that of class; the only difference is that the name of the CLASS IS WRITTEN IN ITALICS

true

best to use the abstract class with multiple objects

Class Diagram

used most widely to construct software applications

Class Diagram

It not only represents a static view of the system but also all the major aspects of an application.

Class Diagram

A collection of class diagrams as a whole represents a system.

meaningful

(class diagram key points) To describe a complete aspect of the system, it is suggested to give a ? name to the class diagram.

advance

(class diagram key points) The objects and their relationships should be acknowledged in ?.

methods

(class diagram key points) The attributes and ? (responsibilities) of each class must be known.

specified

(class diagram key points) A minimum number of desired properties should be ? as more number of the unwanted property will lead to a complex diagram.

describe

(class diagram key points) Notes can be used as and when required by the developer to ? the aspects of a diagram.

redrawn

(class diagram key points) The diagrams should be ? and reworked as many times to make it correct BEFORE PRODUCING its final version

public class Person
{
public String name;
public int age;
public void showDetails()
{code}
}

Type the equivalent code:

Constructor

a method-like construct that has the same name as your class
name

false

Constructors DOES have any return type, even void.

true

(true of false) There is always at least ONE constructor for each class, if the writer does not provide a constructor, Java will provide the default, no-argument, empty-bodied constructor.

Constructor's Golden Rule

There is always at least one constructor for each class, if the writer does not provide a constructor, Java will provide the default, no-argument, empty-bodied constructor.

this

Java Keyword: this is a reference variable that refers to the current object.

current

(usage of 'this' keyword) this can be used to refer ? class instance variable

class method

(usage of 'this' keyword) this can be used to invoke current ? (implicitly)

constructor

(usage of 'this' keyword) this() can be used to invoke current class ? .

passed

(usage of 'this' keyword) this can be ? as an argument in the method call.

constructor

(usage of 'this' keyword) this can be passed as argument in the ? call.

return

(usage of 'this' keyword) this can be used to ? the current class instance from the method.

instance method

called thru the created object

static method

is called thru the class name

Integer class

found under the java.lang package and has a static method
parseInt() that can accept an String integer format that will return an int value.

Integer.parseInt(strNum);

Since the parseInt() method is static, then we call the method thru the name of the class, ? .

Encapsulation, Inheritance, and Polymorphism

Object Oriented Programming Language supports
three main features:

Encapsulation

(OOP 3 main features) Allows you to protect your data from direct access

Encapsulation

(OOP 3 main features) It also provides a common interface that makes them accessible and guards the state of your data by checking the correctness of the values assigned before applying the actual change.

Encapsulation

(OOP 3 main features) It also allows you to create methods that can be called later in your code and the users or callers of those methods need not worry on how the method was implemented.

Encapsulation

(OOP 3 main features) It also allows you to create methods that can be called later in your code and the users or callers of those methods need not worry on how the method was implemented.

Encapsulation

(OOP 3 main features) We can create a fully encapsulated class in Java by making all the data
members of the class private. Now we can use setter and getter
methods to set and get the data in it.

Encapsulation

(OOP 3 main features) EXAMPLE: Package, Access Modifiers

Java Source File Layout

Package – Import – Classes

number of statements per part in PACKAGE

0 to 1 statement

number of statements per part in IMPORT

0 to many

number of statements per part in CLASSES

0 to many

Packages

refer to subdirectories

Packages

may contain classes or sub-packages

Inheritance

(OOP 3 main features) way to reuse objects, carrying over what
was already created and allowing added methods and
attributes to be written on top of what you already have.

Inheritance

(OOP 3 main features) This useful feature allows programmers to reuse what was already coded and not making them rewrite codes and produce redundancies.

Inheritance

(OOP 3 main features) Reusing code can make the runtime of your application faster by eliminating duplicate codes.

class

(terms used in INHERITANCE) is a group of objects which have common properties. It is a template or blueprint from which objects are created.

sub/child class

(terms used in INHERITANCE) which inherits the other class. It is also called a derived class, or extended class

super/parent class

(terms used in INHERITANCE) class from where a subclass inherits the features. It is also called a base class

Reusability

(terms used in INHERITANCE) As the name specifies, reusability is a mechanism which facilitates you to reuse the fields and methods of the existing class when you create a new class. You can use the same fields and methods already defined in the previous class.

syntax of Java Inheritance

class Subclass-name extends Superclass-name

extends

(terms used in INHERITANCE) indicates that you are making a new class that derives from an existing class. The meaning of the term is to Increase the functionality.

Java Inheritance

name the example (OOP features)

Polymorphism

is another process that will allow you to change the method implementation during runtime by having a declared type of a certain class and implements the methods of the sub-type (subclass) also known as Virtual Method Invocation (VMI).

Polymorphism

EXAMPLE: Method Overloading, Method Overriding,
Covariant Return Type, Instanceof Operator, etc.

thread

a Virtual CPU (you may think of a virtual CPU as a virtual machine). It contains three things, the CPU (Thread Class), Code and the Data.

false

Java applications CANNOT run several threads.

Multi-threading

makes use of these three elements and creates its own independent runtime process inside a running Java Application. It is extremely useful in practice. For example, a browser should be able to simultaneously download multiple images while accessing other data storage devices or printing a document.