This document provides an overview of object-oriented programming concepts in Java including objects and classes, encapsulation, inheritance, polymorphism, and language basics. It discusses key OOP concepts like access modifiers, constructors, interfaces, nested classes, anonymous classes, method overloading. It also covers polymorphism through examples. Finally, it lists some important methods like clone, equals, finalize and language features like final, abstract keywords and exception handling.

1. OOPs & JAVA
By Sandesh Sharma

2. Contents

Objects & Classes

Encapsulation

Composition, Inheritance and Delegation

Polymorphism

Language Basics

3. Objects & Classes

Variable
− Access Modifiers

Private

Public

Default

Classes
− Constructors
− Interface
− Nested Clasess
− Anonym Classes

Objects

4. Access Modifier

public modifier—the field is accessible from all classes.

private modifier—the field is accessible only within its own
class.
public class Bicycle {
private int cadence;
private int gear;
private int speed;
public Bicycle(int startCadence, int
startSpeed, int startGear) {
gear = startGear;
cadence = startCadence;
speed = startSpeed;
}
}

5. Classs
public class Bicycle {
// the Bicycle class has
// three fields
public int cadence;
public int gear;
public int speed;
// the Bicycle class has
// one constructor
public Bicycle(int startCadence, int startSpeed, int startGear) {
gear = startGear;
cadence = startCadence;
speed = startSpeed;
}
// the Bicycle class has
// four methods
public void setCadence(int newValue) {
cadence = newValue;
}
public void setGear(int newValue) {
gear = newValue;
}
public void applyBrake(int decrement) {
speed -= decrement;
}
public void speedUp(int increment) {
speed += increment;
}
}

6. Interface
interface Bicycle {
// wheel revolutions per minute
void changeCadence(int newValue);
void changeGear(int newValue);
void speedUp(int increment);
void applyBrakes(int decrement);
}
class ACMEBicycle implements Bicycle {
int cadence = 0;
int speed = 0;
int gear = 1;
// The compiler will now require that methods
// changeCadence, changeGear, speedUp, and applyBrakes
// all be implemented. Compilation will fail if those
// methods are missing from this class.
void changeCadence(int newValue) {
cadence = newValue;
}

7. Method Overloading
public class DataArtist {
...
public void draw(String s) {
...
}
public void draw(int i) {
...
}
public void draw(double f) {
...
}
public void draw(int i, double f) {
...
}
}

8. Constructor
public Bicycle(int startCadence, int
startSpeed, int startGear) {
gear = startGear;
cadence = startCadence;
speed = startSpeed;
}
Rectangle rectTwo = new Rectangle(50, 100);

9. Nested Classes
class OuterClass {
...
class NestedClass {
...
}
}
class OuterClass {
...
static class StaticNestedClass {
...
}
class InnerClass {
...
}
}

10. Anonymous Classes
HelloWorld frenchGreeting = new HelloWorld() {
String name = "tout le monde";
public void greet() {
greetSomeone("tout le monde");
}
public void greetSomeone(String someone) {
name = someone;
System.out.println("Salut " + name);
}
};

11. Polymorphism
public class RoadBike extends Bicycle{
// In millimeters (mm)
private int tireWidth;
public RoadBike(int startCadence,
int startSpeed,
int startGear,
int newTireWidth){
super(startCadence,
startSpeed,
startGear);
this.setTireWidth(newTireWidth);
}
public int getTireWidth(){
return this.tireWidth;
}
public void setTireWidth(int newTireWidth){
this.tireWidth = newTireWidth;
}
public void printDescription(){
super.printDescription();
System.out.println("The RoadBike" + " has " + getTireWidth() +
" MM tires.");
}
}

12. Polymorphism
public class TestBikes {
public static void main(String[] args){
Bicycle bike01, bike02, bike03;
bike01 = new Bicycle(20, 10, 1);
bike02 = new MountainBike(20, 10, 5, "Dual");
bike03 = new RoadBike(40, 20, 8, 23);
bike01.printDescription();
bike02.printDescription();
bike03.printDescription();
}
}

13. Language Basics

clone()

equals()

finalize()

getClass()

hashCode()

ToString()

final

Abstract

String / stringbuilder / stringbuffer

Try / catch

14. thAnks

Email at ersandeshsharma[at]gmail.com