Java Programming - 04 object oriented in java

Module 04 – Object Oriented in Java
Danairat T.
Line ID: Danairat
FB: Danairat Thanabodithammachari
+668-1559-1446

Fundamental Java Programming
The Course Outline
Module 01 – Introduction to Java
Module 02 – Basic Java Programming
Module 03 – Control Flow and Exception Handling
Module 05 – Java Package and Access Control
Module 06 – Java File IO
Module 07 – Java Networking
Module 08 – Java Threading

• Java Class
• Java Object
• Java Variable
• Java Method and Constructor
• Abstraction
• Encapsulation
• Inheritance
• Polymorphism

Java Class
A class is a blueprint or prototype from which objects are
created. This section defines a class that models the state
and behavior of a real-world object. It intentionally focuses on
the basics, showing how even a simple class can cleanly
model state and behavior.

Java Object
Java Object is conceptually similar to real-world objects.
They consist of state and behavior.
An object stores its state in fields (variables) and exposes its
behavior through methods.
Methods operate on an object's internal state. Hiding internal
state is known as data encapsulation
Class
Object 1
Object 2
Blueprint
Instance

Java Class Syntax
["public"] ["abstract"|"final"]"class" Class_name
["extends" object_name] ["implements"
interface_name]
"{"
// properties declarations
// behavior declarations
"}"

Class Members
Class consists from two main members:-
• Variable
• Method
Variable
Member variables in a class—these are called fields.
- Class – static member
- Object – instance member
Variables in a method or block of code—these are called local variables.
Variables in method declarations—these are called parameters.

Method
[ "public" | "private" | "protected" ] [ "final" ]
[ "static" | "abstract" ]
return_data_type method_name "(" parameter_list ")"
"{"
// some defining actions
"}"
public static void example1() {}
public static int add2(int x) {x+=2; return x;}
public static double example3(int x, double d) {return x*d;}
public static void example4(int x, int y, boolean flag) {}
public static void example5(int arr[]) {} // note: this is object

Type of Java Method
1. Constructor methods
These allow class objects to be created with fields initialized to values
as determined by the methods' parameters. This allows objects to start
with values appropriate to use
public Box() {length=0;width=0;height=0;} // default is point public Box(int l,int w,int h) // allows
giving initial size {length=l; width=w; height=h;}
2. Accessor (or observer) methods read property (ie. field variable) values
and are conventionally named getField() or whatever the property is
called.
3. Mutator (or transformer) methods set property values and are often
named setField() etc. Mutators can be used to ensure that the
property's value is valid in both range and type.
4. Helper methods support modular of code structure in a unit of working.

Overloading Method
The Java programming language supports overloading methods,
and Java can distinguish between methods with different method
signatures (Method Name, Argument Type, Number of Argument).
public class TouchPointer {
...
public void draw(int i) {
...
}
public void draw(double f) {
...
}
public void draw(int i, int j) {
...
}
}

Constructor
When you create a new instance (a new object) of a class using the new
keyword, a constructor for that class is called. Constructors are used to
initialize the instance variables (fields) of an object. Constructors are
similar to methods, but with some important differences.
• Constructor name is class name. Eg. YourClassName() {}
• Default constructor. If you don't define a constructor for a class, a
default parameterless constructor is automatically created by the
compiler. The default constructor calls the default parent constructor
(super()) and initializes all instance variables to default value.
• Default constructor is created only if there are no constructors. If you
define any constructor for your class, no default constructor is
automatically created.

Differences between methods and
constructors
1. There is no return type given in a constructor signature
(header). The value is this object itself so there is no need
to indicate a return value.
2. There is no return statement in the body of the constructor.
3. The first line of a constructor must either be a call on
another constructor in the same class (using this), or a call
on the superclass constructor (using super). If the first line
is neither of these, the compiler automatically inserts a call
to the parameterless super class constructor.

LAB – ConstructTest1
public class ConstructTest {
int value1;
int value2;
ConstructTest() {
value1 = 10;
value2 = 20;
System.out.println("Inside Constructor");
}
public void display() {
System.out.println("Value1 === " + value1);
}
public static void main(String[] args) {
ConstructTest c1 = new ConstructTest();
c1.display();
}
}
Inside Constructor
Value1 === 10
Value2 === 20
Creating Object HereCreating
Reference
Activating Method

LAB - Constructor Overloading
class ConstrutOverloadDemo {
int value1;
int value2;
ConstrutOverloadDemo() {
value1 = 10;
value2 = 20;
System.out.println("Inside 1st Constructor");
}
ConstrutOverloadDemo(int a) {
value1 = a;
System.out.println("Inside 2nd Constructor");
}
ConstrutOverloadDemo(int a, int b) {
value1 = a;
value2 = b;
System.out.println("Inside 3rd Constructor");
}
public void display() {
}
public static void main(String[] args) {
ConstrutOverloadDemo c1 = new
ConstrutOverloadDemo();
ConstrutOverloadDemo(30);
ConstrutOverloadDemo(30, 40);
c1.display();
c2.display();
c3.display();
}
}

LAB - Constructor Chain
class ConstrucChainDemo{
int value1;
int value2;
ConstrucChainDemo(){
value1 = 1;
value2 = 2;
System.out.println("Inside 1st Parent Constructor");
}
ConstrucChainDemo(int a, int b){
value1 = a;
value2 = b;
Syastem.out.println("Inside 2nd Parent Constructor");
}
}
class ConstrucChild extends ConstrucChainDemo{
int value3;
int value4;
ConstrucChild(){
super(11,22);
value3 = 3;
value4 = 4;
System.out.println("Inside the Constructor of Child");
}
public void display(){
System.out.println("Value1 === "+value1);
}
}
public static void main(String args[]){
ConstrucChild c1 = new ConstrucChild();
c1.display();
}

Object Oriented History
The sense of object-oriented programming term seems to
make their first appearance at MIT in the late 1950s
Object-oriented programming is modeled on how in the
real world objects are made up of many kinds of smaller
objects.
The Smalltalk language, which was developed at Xerox
PARC (by Alan Kay and others) in the 1970s, introduced
the term object-oriented programming to represent the
pervasive use of objects and messages as the basis for
computation.

Abstraction
Abstraction(hiding implementation) focuses on the
outside view of an object.. (i.e. the interface)
Abstraction is an essential element for OO which
manages the complexity. In a sense when someone
works on a computer not necessary that he should
know the working of each and every part of the
computer.
interface Customer {
void printCustomer (int i);
}

Encapsulation
Encapsulation (hiding information) prevents clients from
seeing its inside view, where the behavior of the
abstraction is implemented
It is the mechanism that binds together state and behavior
in manipulates and keeps both safe from outside
interference and misuse.
class Customer {
private String name;
public String getName() { return name; }
public void setName(String name) { this.name = name; }
}

Inheritance
It is the process by which one object acquires the properties
of another object. This supports the hierarchical
classification. Without the use of hierarchies each object
would need to define all its characteristics explicitly.
However by use of inheritance, an object need only define
those qualities that make it unique within its class.
Java use “extend” keyword to inherit properties and
behavior from super to its sub class.
class Customer {
String name;
public String getName() {
}
}
class MemberCustomer extends
Customer {
int collectedPoints;
}

Polymorphism
The ability of the object design to group object behavior
from different types.
So by using this, one object can be treated like another
even it came from difference hierarchy.
The programmers can focus on selected behavior by no
need to know the exact type of object in advance and this
is being implemented at runtime.

Defining the Behavior
public interface IFace_Printable {
public void printNow();
}

Defining Classes which are the same
behavior
public class CustomerInfo implements IFace_Printable{
@Override
public void printNow() {
System.out.println("Read Customer Table... CustomerInfo. Done.");
}
}
public class ProductInfo implements IFace_Printable{
@Override
public void printNow() {
System.out.println("Reading Product Table... ProductInfo. Done.");
}
}

Create Polymorphic Method
public class PrintServer {
private IFace_Printable iFacePrintable;
PrintServer(IFace_Printable iFacePrintable){
this.iFacePrintable = iFacePrintable;
}
public void printNowWraper(){
iFacePrintable.printNow();
}
}

Create Test Client for the Polymorphic Method
public class PrintClientApplication {
private static CustomerInfo customerInfo = new CustomerInfo();
private static ProductInfo productInfo = new ProductInfo();
public static void main(String [] args) {
new PrintServer(customerInfo).printNowWraper();
new PrintServer(productInfo).printNowWraper();
}
}

Danairat T.
Line ID: Danairat
FB: Danairat Thanabodithammachari
+668-1559-1446
Thank you

Java Programming - 04 object oriented in java

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Java Programming - 04 object oriented in java