OOP Concept
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This is oop file for you to learn more about OOP in java programming!
![13
Encapsulation
public class TestJava {
private int id;
private String name;
private int age;
public void setId(int id){this.id=id;}
public int getID(){return id;}
public void setName(String name){this.name=name;}
public String getName(){return name;}
public void setAge(int age){
if(age<0){
this.age=1;
}else{
this.age=age;
}
}
public int getAge(){return age;}
}
Public class DemoEncap{
public static void main(String args[]){
TestJava obj= new TestJava();
obj.setId(100);
obj.setName("Hong");
obj.setAge(-1);
System.out.println("ID:"+
obj.getID() + "nName:"+ obj.getName()+
"nAge:"+ obj.getAge());
}
}](https://image.slidesharecdn.com/oop-160622090834/85/OOP-Concept-13-320.jpg)
![16
Inheritance
class ClassA{
int a=;
public void add(int x, int y){
a = x+y;
System.out.println("The sum of the given numbers:"+a);
}}
public class ClassB extends ClassA{
public void multiplication(int x, int y){
a= x*y;
System.out.println("The product of the given
numbers:"+a);
}
public static void main(String args[]){
int a = 20, b = 10;
ClassB sub = new ClassB ();
sub.add(a, b);
sub.multiplication(a, b);
}
}
ο± α§αα ααα αααΎαααΆα ClassααΈα ααΊ
ClassA αα·αClassB α αClassBααααΎααΆα
Inheritannce αααααΈ ClassAα](https://image.slidesharecdn.com/oop-160622090834/85/OOP-Concept-16-320.jpg)
![17
Inheritance
ο± α§αα ααα
public class Sub_class extends Super_class {
int num = 10; //display method of sub class
public void display(){
System.out.println("This is the display method of subclass");}
public void my_method(){
Sub_class sub = new Sub_class();//Instantiating subclass
sub.display();//Invoking the display() method of sub class
super.display();//Invoking the display() method of superclass
System.out.println("value of the variable named num in sub class:"+ sub.num);
//printing the value of variable num of superclass
System.out.println("value of the variable named num in super class:"+ super.num);
}
public static void main(String args[]){
Sub_class obj = new Sub_class();
obj.my_method();
}
class Super_class{
int num = 20; //display method of superclass
public void display(){
System.out.println("This is the display method
of superclass");}}](https://image.slidesharecdn.com/oop-160622090834/85/OOP-Concept-17-320.jpg)
![28
Polymorphism
α αΎα’αααΈαα
ααΆ Runtime Polymorphism ?
ο± Method overriding ααΊααΆα§αα ααα αα’ α
αΆααααΆαα runtime polymorphism α
Y obj = new Y(); //Parent class reference can be assigned to child object X obj = new Y();
ο± ααΆαααααΎααα
αααΎαα§αα αααα αΎαααΈαααααΆααα
αΆαα
public class X {
public void methodA() //Base class method
{ System.out.println
("hello, I'm methodA of class X");
}
}
public class Y extends X {
public void methodA() //Derived Class method
{ System.out.println ("hello, I'm methodA of class Y");
}
}
public class Z {
public static void main (String args []) {
X obj1 = new X(); // Reference and object X
X obj2 = new Y(); // X reference but Y object
obj1.methodA();
obj2.methodA();
}
}
Output:
hello, I'm
methodA of
class X
hello, I'm
methodA of
class Y](https://image.slidesharecdn.com/oop-160622090834/85/OOP-Concept-28-320.jpg)
![29
Polymorphism
α αΎα’αααΈαα
ααΆ Compile time Polymorphism ?
ο± Method overloading ααΊααΆα§αα ααα αα’ α
αΆααααΆαα compile time polymorphism α
Y obj = new Y(); //Parent class reference can be assigned to child object X obj = new Y();
ο± ααΆαααααΎααα
αααΎαα§αα αααα αΎαααΈαααααΆααα
αΆαα
class X {
void methodA(int num) {
System.out.println ("methodA:" + num);
}
void methodA(int num1, int num2)
{
System.out.println ("methodA:" + num1 + "," + num2);
} double methodA(double num) {
System.out.println("methodA:" + num); return num;
}
} class Y {
public static void main (String args []) {
X Obj = new X(); double result; Obj.methodA(20);
Obj.methodA(20, 30); result = Obj.methodA(5.5);
System.out.println("Answer is:" + result);
}
}
Output:
methodA:20
methodA:20,30
methodA:5.5
Answer is:5.5](https://image.slidesharecdn.com/oop-160622090834/85/OOP-Concept-29-320.jpg)
![31
Polymorphism
α αΎα’αααΈααΆβMethod Overloading ?
ο± Method Overloading ααΆαααα αα αΌα
αααα βα αααααα αα
α
αΆααα½α αα·α data type αα parameter α
class Overload
{
void demo (int a) {
System.out.println ("a: " + a);
}
void demo (int a,int b){
System.out.println ("a and b: " + a + "," + b);
}
double demo(double a) {
System.out.println("double a: " + a); return a*a;
}
}
class MethodOverloading {
public static void main (String args []) {
Overload Obj = new Overload(); double result; Obj .demo(10); Obj .demo(10, 20);
result = Obj .demo(5.5); System.out.println("O/P : " + result);
}
}
Output:
a: 10
a and b: 10,20
double a: 5.5
O/P : 30.25](https://image.slidesharecdn.com/oop-160622090834/85/OOP-Concept-31-320.jpg)
![33
Polymorphism
α αΎα’αααΈααΆβMethod Overriding ?
ο± Method Overriding ααΆαααα αα αΌα
αααα βα
αΆααα½α αα·α data type αα parameter α αΌα
αααα α
public class BaseClass { public void methodToOverride() //Base class method
{
System.out.println ("I'm the method of BaseClass");
}
}
public class DerivedClass extends BaseClass {
public void methodToOverride() //Derived Class method
{
System.out.println ("I'm the method of DerivedClass");
}
}
public class TestMethod {
public static void main (String args []) { // BaseClass reference and object
BaseClass obj1 = new BaseClass(); // BaseClass reference but DerivedClass object
BaseClass obj2 = new DerivedClass(); // Calls the method from BaseClass class
obj1.methodToOverride(); //Calls the method from DerivedClass class obj2.methodToOverride();
}
}
Output:
I'm the method of BaseClass I'm the method
of DerivedClass](https://image.slidesharecdn.com/oop-160622090834/85/OOP-Concept-33-320.jpg)
OOP Concept
- 1. Java Presentation αααααααα αααΌα αα αα αα αα ααα α ααΈ Korea Software HRD Center www.kshrd.com.kh ααα α»αααΈα€α ααα αααΉα αα·ααΆ ααα ααΆααΈαα αΆα αααβα ααα»α αααΈααα ααα αα αααααΆ ααα ααΈα ααα αα
- 2. ααααΆ αα αααΆαααα ααα α»αααΈ α€ αααααΆαααα ααΌαααααΆ αααααΉαααααααΆααΆJava αααΆααα·α ααα ααΆααΈαα αΆα αααβα αα»α ααΈααα ααα αα αααααΆ ααα ααΈα ααα α
- 3. ααΆαα·ααΆ 1. α αΎα’αααΈααΆ OOP? 2. α αΎα’αααΈααΆβClass αα·α Object ? 3. α αΎα’αααΈααΆ Encapsulation ? 4. α αΎα’αααΈααΆ Inheritance? 5. α αΎα’αααΈααΆ Abstraction (Abstract class Interface) 6. α αΎα’αααΈααΆ Polymorphism ? 3
- 4. 4 OOP ο± ααΆααααΆ OOP ααΆααααααΆ Object Oriented Programming α αΎαααΈαα½αα ααααααααα αααα αΆ ααΆααα‘αΆαα ο± ααΌα αΆ αααααααααααα OOP ααΊααΆβclass α αΎαααΈααΆ ααααΆ Program αα½αααΆααααααααΆ OOP αααααααΆα Program α ααααΆααααααΌααααααα α£αααΆ αααΊα α αΎα’αααΈαα ααΆ OOP ? 1. Encapsulation 2. Inheritance 3. Polymorphism
- 5. 5 OOP ο± Class ααΊααΆαααααΆαααΌααααααΆαααααααΎ Object α¬βααΆαα αααααααααααα Object α ο± Java ααααααΎααααααα·ααααααα Class α αΎαααΈαααααΎ Object α α αΎα’αααΈαα ααΆ Class ? ο± Instance Variable ( Data Member ) αα·α Method α α Instance Variable αα·α Method ααΊααΆ Member αααα Classα
- 6. 6 OOP class class-name{ type instance-variable1; type instance-variable2; //β¦. type instance-variableN; type methodname 1(parameter-list){ //body of method } type methodname 2(parameter-list){ //body of method } type methodname N(parameter-list){ //body of method } ααΆααααααΌαα αααα Class
- 7. 7 OOP Class Vehicle{ int passengers; //number of passengers int fuelcap; //fuel capacity in liters int kpl; //fuel consumption in kilometers per liter } ααΆααααααΎ Class o Class α’αΆα αααααΎ ααΌαααααααααα·ααααα (Data type) ααααΈαα½α α αα α»αααααΈαααα ααααααα αα·αααααααααΈα ααααα ααααΆβ Vehicle αα αΎααααΎααααααααααΎααα ααααααα αΎαααΈααααααΆα Objects α Vehicle minivan = new Vehicle();
- 8. OOP ο± Object ααΊααΆ Instance αααα Classα ο± Object ααΆα’αααΈαα ααα ααΆαα α·ααα α½ααααΎα αΌα ααΆ ααα αααΆαΌ αΌβα‘αΆα αααααα α αα·α ααΆααααΌ αααβ¦α α αΎα’αααΈαα ααΆ Object ? ο± Object ααΆα State αα·α Behaviorα οΌ State ααΆααααα α¬ ααΆ ααααΆαααααααΆαααααααΎ Object α Ex1: ααααααΆα αααα» α ααΆαααα α’αΆα ααα α Ex2:αααΆαΌ αΌααΆα ααα ααα αααα αααΆ αα ααααΎαααΈαααΆαΌβ¦α οΌ Behavior ααΆα’αααΈα α Object α’αΆα ααααΎααΆαα Ex1: ααααααΆα α αΎα α α α’ααα α»α αα ααΆα αααΎα β¦.α Ex2:ααΌα ATM ααΆα ααααααΆαα αααααααΆαα β¦. α
- 9. 9 OOP ααααααααααΎ Objects Vehicle minivan = new Vehicle(); β’ αααΎαααααααΆαα’αααα α·ααα½αααΆαααα ααααΆ minivan α αααΆα Vehicle ααΆααααααα αα·ααααα (Reference of Object)α β’ new operator αααααΎ ααΈαΆαΆαααα α»αβMemory αααα Object αα½ααα αΎαααααα Reference αα α²αα Object α αα α β’ Reference ααΆα’αΆααα αΆ ααα Object αα αα α»α Memory α ααααααΎ ααΈαΆαΆααα α new α
- 10. 10 OOP ααααααααααΎ Methods ret-type methName(param-list){ //body of method } οΌ ret-type αααα αΆ ααααΈααααααααα·αααααα αααα αΌαααΆααααααα²αα Method α αα’αΆα ααΆ ααααααααα·αααααααααΆ α¬ α’αΆα αααααααααΆβClass α ααααΎαααΆααααααΎ α αΎα α οΌ Method αα·αααα αΌαααΆαααααα ααααα α ααααααααααα·ααααααααααααα αΌαα ααΆ void α οΌ methName ααΆααα αααααα Method α οΌ param-list ααΆααααααααα·ααααα αα·α ααα ααα’αααα αα·ααααααΎααααααα α ααααααααααα α αααΈαααα α α αααα α ααααα (,)α
- 11. 11 Encapsulation ο± Encapsulation αααΆααααααα½ααα OOP conceptα ο± ααααΎαα’αΆα Field αα αα α»α class αα½ααα·αα’ααααα α αα’αΆαααΆαααΆα access α αΌαααΈ class ααααααΆαααΊ variable αα αα α»α class αα½αααα αΌαααΆα hide ααΈ class αα αα αΎααα’αΆα access ααΆααΆαααα method getter() αα·αβsetter()α α αΎα’αααΈαα ααΆ Encapsulation ?
- 12. 12 Encapsulation ο± Field αααα class α’αΆα ααΆαα αααΆ Read-only α¬ Write-only. ο± Class α’αΆα αααααααααααααΆαααααα α»ααα αααΎ data α αααααααΎαααααΆαα codeα ααααα αα·αααα Encapsulation ? ο± α’αααααααααΎαααααΆαα class αα·α ααααΈαααααα α class ααα α»α(store) αα·αααααα ο± Class α’αΆα αα αΌαααΌα data type αα field αα½αα ο± α’αααααααααΎαααααΆααα class αα·αααα αΌαααΆααα αΌα code ααααααα
- 13. 13 Encapsulation public class TestJava { private int id; private String name; private int age; public void setId(int id){this.id=id;} public int getID(){return id;} public void setName(String name){this.name=name;} public String getName(){return name;} public void setAge(int age){ if(age<0){ this.age=1; }else{ this.age=age; } } public int getAge(){return age;} } Public class DemoEncap{ public static void main(String args[]){ TestJava obj= new TestJava(); obj.setId(100); obj.setName("Hong"); obj.setAge(-1); System.out.println("ID:"+ obj.getID() + "nName:"+ obj.getName()+ "nAge:"+ obj.getAge()); } }
- 14. 14 Inheritance α αΎα’αααΈαα ααΆ Inheritance? ο± Inheritance ααΊααΆααααααα αααΈ Class αα½ααα Class αα½ααααααααα α ο± Class α αααααα ααααα’αΆααααα ααΆ Parent Class αα αΎα Class α αααα½α ααααα ααΆ Child Classα ο± Inheritance α’ααααα α α·α²αα Class αα½αααααααΎαααααΆαααα properties αα·α methods αα class αααααααα ααΆα α ο± Inheritance ααΊααΆ compile-time mechanism α super-class α’αΆα ααΆα subclasses αααα½αα αΆααα½αα αααΆααα subclass ααΆαααα ααα super-class αα½ααααΆααα αα α
- 15. 15 Inheritance α αΎ Inheritance ααααΎααΆααααΆ α αΌα αααα ? ο± Extends: αα αα α»αJava α αΎαααΈααααΎααΆα Inheritance ααΈ Parent Class αα Child Class αααΎαααα αΌαααααααΎαααααΆαα Keyword Extendsα ο± Super: ααααααααΎαααααααΆααααΆαα ααααααMemberαααα Classαα ααααΈ α α Method αα·α Variable αααα Classαααα·α ClassααΌα αΌα αααα α ο± Implement: ααΆKeyword αα½αα αα’ααααα α αα’αΆα Class ααααΎααΆαααα½ααα αααΈ Interfaceα
- 16. 16 Inheritance class ClassA{ int a=; public void add(int x, int y){ a = x+y; System.out.println("The sum of the given numbers:"+a); }} public class ClassB extends ClassA{ public void multiplication(int x, int y){ a= x*y; System.out.println("The product of the given numbers:"+a); } public static void main(String args[]){ int a = 20, b = 10; ClassB sub = new ClassB (); sub.add(a, b); sub.multiplication(a, b); } } ο± α§αα ααα αααΎαααΆα ClassααΈα ααΊ ClassA αα·αClassB α αClassBααααΎααΆα Inheritannce αααααΈ ClassAα
- 17. 17 Inheritance ο± α§αα ααα public class Sub_class extends Super_class { int num = 10; //display method of sub class public void display(){ System.out.println("This is the display method of subclass");} public void my_method(){ Sub_class sub = new Sub_class();//Instantiating subclass sub.display();//Invoking the display() method of sub class super.display();//Invoking the display() method of superclass System.out.println("value of the variable named num in sub class:"+ sub.num); //printing the value of variable num of superclass System.out.println("value of the variable named num in super class:"+ super.num); } public static void main(String args[]){ Sub_class obj = new Sub_class(); obj.my_method(); } class Super_class{ int num = 20; //display method of superclass public void display(){ System.out.println("This is the display method of superclass");}}
- 18. 18 Inheritance ο± α§αα ααα Public Interface Motor{ void speedUp(int increment); } class MyMotor implement Motor{ int speed = 0; void speedUp(int increment) { speed = speed + increment; } void printStates() { System.out.println("My motor speed" +speed); } }
- 19. 19 Inheritance ααααααααα Inheritance ο§ Single inheritance in java ο§ multilevel inheritance ο§ multiple inheritance ο§ hybrid inheritance ο§ hierarchical inheritance
- 20. 20 Abstraction ο± ααΆαα programming languages α αα ααααα abstractions α ο± ααα½αααααααα αΆααααααααααα αααΆαααΆααα α»ααα ααααααα αΆ (α ααααααα αααααα αααα αΆαααααααα αα·α ααααα αα·αα abstraction α α αΎα’αααΈαα ααΆ Abstraction? ο± Abstraction αααΆααΆ ααΆαααΆαααα½ααα object-oriented programming ο± Abstraction ααΆ αΆααααΎαααΆαααααΆααααααΆαΆααααα αααΈααΆαα’αα· ααααΆαα’ααα ααα( implementation)αα αΎααααααΆ αα α½ ααΈ α αα½αα ααα ααα’αααααααααΎαααααΆααα
- 21. 21 Abstraction ο± Abstract class ααΆβclass αα½αα αααααααΆαααΆ abstract α ο± Abstract method ααΊααΆ methodαα½αα αααααααΆαααΆ abstract α α αΎα’αααΈαα ααΆ Abstract class? ο± Abstract Class ααααΆαααα abstract method αα½αα¬ααααα αΎαα Syntax: abstract class (class name){ //abstract methods }
- 22. 22 Abstraction α αΆαααΆαα o αααα·αααΆααΆα abstract method α αααΎαα α αααα»α class αααα½α α αΉα class αααΌαααααΆ abstract α o αααα·αααΆα’ααααααααα»ααα extend abstract classα αααΎααααααΆα abstract method α’αααααα·ααααΌααααααααΆα implementationα α α αα method α¬ α αααΎα αα class α αΉα ααΆαΆ αααΆ abstract classα
- 23. 23 Abstraction α αΎα’αααΈαα ααΆ Interface ? ο± Interface αααΎααα αΌα ααΆ class αααΆαααααα·ααααααΆ class ααα ο± Interface ααΊααααααΎαα default abstract (ααΆαααα ααα method signature αααα α body αα)α ο± Interface α αΎα α½ ααΈααΆ blueprint (αααα)ααΆαααΆαα class α ο± Interface αα·αα’αΆα αααααΎ object ααΆαααα
- 24. 24 Abstraction αα α’αααΈαααΎαααα αΌαααααααΎ Interface ? ο± ααααΎα²αα abstract αα½αβββααΆαααααααααααα α ο± αΆαααα interface αααΎαα’αΆα αααα α·α αα·ααΆααααααααααα multi-inheritanceα ο± αα’αΆα ααα αΌαααααααΎαααααΆααα αΎαααΈααΆαααα loose coupling α
- 25. 25 Abstraction 1. Abstract class VS Interface: ααΆαααΌα ααααΆ ααΆαβAbstract class & Interface: ο± α’αΆα α²αα abstraction αα·αα’αΆα ααααααΆα abstract method α ο± Abstract class & Interface αα·αα’αΆα ααΆ instantiatedα
- 26. 26 Abstraction Abstract class Interface 1) Abstract class α’αΆα ααΆαα¬αααα α(0%-100%) abstract methodα Interface ααα αΌαα ααΆα (100%) abstract methodα 2) Abstract class αα·αββsupport multiple inheritanceα Interface supports multiple inheritance. 3) Abstract class α’αΆα ααΆα final, non-final, static and non-static variablesα Interface α’αΆα ααΆα static and final variables αααΆααα ααα 4) Abstract class α’αΆα ααΆα static methods, main method and constructorα Interface αα·αααΆα static methods, main method and Constructorα 5) Abstract class α’αΆα αααααβimplementation ααααinterfaceα Interface αα·αα’αΆα αααααβimplementation αααα abstract class ααΆαααα 6) The abstract keyword ααΊααααααΎα αΎαααΈααααααΆαα abstract classα The Interface keyword ααΊααααααΎα αΎαααΈααααααΆαα Interfaceα 7) Example: public abstract class Shape{ public abstract void draw(); } Example: public interface Drawable{ void draw(); } ααΆαααααααΆ ααΆαβAbstract class & Interface:
- 27. 27 Polymorphism ο± Polymorphism ααααΈααΆαααααααβααΈαααΆααααΊ poly αα·α morphs α ο± Poly ααΆααααααΆβααααα αΎα αα·α morphs ααΆααααααΆ ααΆαααα α ο± polymorphism ααΆαααΈαααααααααα αα α»α java ααΊ 1) compile time polymorphism(static polymorphism) 2) runtime polymorphism (Dynamic polymorphism ) α αΎα’αααΈαα ααΆ Polymorphism? ο± αααΎαα’αΆα α’ααα α polymorphism αα αα α»α java α α method overloading αα·α method overriding α
- 28. 28 Polymorphism α αΎα’αααΈαα ααΆ Runtime Polymorphism ? ο± Method overriding ααΊααΆα§αα ααα αα’ α αΆααααΆαα runtime polymorphism α Y obj = new Y(); //Parent class reference can be assigned to child object X obj = new Y(); ο± ααΆαααααΎααα αααΎαα§αα αααα αΎαααΈαααααΆααα αΆαα public class X { public void methodA() //Base class method { System.out.println ("hello, I'm methodA of class X"); } } public class Y extends X { public void methodA() //Derived Class method { System.out.println ("hello, I'm methodA of class Y"); } } public class Z { public static void main (String args []) { X obj1 = new X(); // Reference and object X X obj2 = new Y(); // X reference but Y object obj1.methodA(); obj2.methodA(); } } Output: hello, I'm methodA of class X hello, I'm methodA of class Y
- 29. 29 Polymorphism α αΎα’αααΈαα ααΆ Compile time Polymorphism ? ο± Method overloading ααΊααΆα§αα ααα αα’ α αΆααααΆαα compile time polymorphism α Y obj = new Y(); //Parent class reference can be assigned to child object X obj = new Y(); ο± ααΆαααααΎααα αααΎαα§αα αααα αΎαααΈαααααΆααα αΆαα class X { void methodA(int num) { System.out.println ("methodA:" + num); } void methodA(int num1, int num2) { System.out.println ("methodA:" + num1 + "," + num2); } double methodA(double num) { System.out.println("methodA:" + num); return num; } } class Y { public static void main (String args []) { X Obj = new X(); double result; Obj.methodA(20); Obj.methodA(20, 30); result = Obj.methodA(5.5); System.out.println("Answer is:" + result); } } Output: methodA:20 methodA:20,30 methodA:5.5 Answer is:5.5
- 30. 30 Polymorphism ο± α’ααααα α α·α²αα interface αα½αα’αΆα ααα αΌαααΆαααααααΎαααααΆααααΆααΌαα αα αα α»α classα ο± αααα α·α αα·ααΆααα½αα’αΆα ααΆα behavior αααααα αα αα α»αααααΈααααααααα α α αΎ Polymorphism ααααΎααΆααααΆ α αΌα αααα ? ο± Behavior ααααααα’ααα αααΎααααααααα data α αααΆαααααααΎαα αα α»ααααα’ααα αα ο± αα αΎα α½ ααΈαααΆ αααΆαααΆαααα αα α»αααΆαα’ααααα α α·α²αα object α αααΆα internal structures α αΎαααΈαα αααααα external interface α ο± Polymorphism ααα αΌαααΆαααααααααΎαααΆ αααΌααΆαααΌαααα α»αααΆα implement inheritance α
- 31. 31 Polymorphism α αΎα’αααΈααΆβMethod Overloading ? ο± Method Overloading ααΆαααα αα αΌα αααα βα αααααα αα α αΆααα½α αα·α data type αα parameter α class Overload { void demo (int a) { System.out.println ("a: " + a); } void demo (int a,int b){ System.out.println ("a and b: " + a + "," + b); } double demo(double a) { System.out.println("double a: " + a); return a*a; } } class MethodOverloading { public static void main (String args []) { Overload Obj = new Overload(); double result; Obj .demo(10); Obj .demo(10, 20); result = Obj .demo(5.5); System.out.println("O/P : " + result); } } Output: a: 10 a and b: 10,20 double a: 5.5 O/P : 30.25
- 32. 32 Polymorphism α αΎ Method Overloading ααααΎααΆααααΆ α αΌα αααα ? 1. Method Overloading α’αΆα ααααΎααΆααα αα α»α class αΌα αααα α¬ αα αα α»α sub-class ααααα α 2. Constructor αα αα α»α Java α’αΆα ααΆ Overloaded 3. Overloaded methods αα½αα ααΆα argument list αααααα 4. Parameter α’αΆα αααααα αα αααΎ type α¬ number α¬α ααΆααααΈαα ααα α 5. αα½ααα’αΆα ααΆα return types αααααα α¬ αΌα αααα α 6. ααααα αΌαααΆααααα ααΆααΆ compile time polymorphism α
- 33. 33 Polymorphism α αΎα’αααΈααΆβMethod Overriding ? ο± Method Overriding ααΆαααα αα αΌα αααα βα αΆααα½α αα·α data type αα parameter α αΌα αααα α public class BaseClass { public void methodToOverride() //Base class method { System.out.println ("I'm the method of BaseClass"); } } public class DerivedClass extends BaseClass { public void methodToOverride() //Derived Class method { System.out.println ("I'm the method of DerivedClass"); } } public class TestMethod { public static void main (String args []) { // BaseClass reference and object BaseClass obj1 = new BaseClass(); // BaseClass reference but DerivedClass object BaseClass obj2 = new DerivedClass(); // Calls the method from BaseClass class obj1.methodToOverride(); //Calls the method from DerivedClass class obj2.methodToOverride(); } } Output: I'm the method of BaseClass I'm the method of DerivedClass
- 34. 34 Polymorphism α αΎ Method Overriding ααααΎααΆααααΆ α αΌα αααα ? 1. α’ααααα α α· α α αΆααααΆαα inherited methods 2. Object type (αα·ααααααΆ reference variable type)α αααΆαα α overridden method αα·αααα αΌαααΆαααααααΎαα ααα runtime 3. Overriding method α’αΆα ααΆα return type αααααα 4. Overriding method αα·αααα αΌαααΆα restrictive access modifier α 5. Abstract methods ααα αΌαααΆαα’αΆα overridden 6. Static αα·α final method αα·αα’αΆα overridden 7. αααα αΌαααΆαααααΆ ααααΆααΆ Runtime polymorphism α