Brief explanation about java and oops concepts "encapsulation" "inheritance" and "interface"

1. INTRODUCTION TO JAVA

2. WHAT IS JAVA?
• Java is an object oriented programming language.
• Java is platform independent.
• Java is used in mobile phones and other embedded devices.

3. HISTORY OF JAVA
• Java was developed by James Gosling from sun microsystems in the
year 1995.
• In January 1996, JDK1.0 was released in the name of OAK.
• The JDK 1.0.2 was the first stable version.
• James Gosling, Mike Sheridan and Patrick Naughton initiated the
green project in June 1991.

4. Versions of java

5. Features of java
• Simple
• Secure
• Portable
• Object-Oriented
• Robust
• Multithreaded
• Architecture neutral
• Interpreted
• High Performance
• Distributed
• Dynamic

6. Types of SDK’s in java
• Java SE
• Java EE
• Java ME
• Java Embedded
• Java DB
• Web Tier
• Java Card
• Java TV

7. Java virtual machine
• Java Virtual Machine is used for converting the bytecode into the
machine understandable format.
• JVM provides an abstraction between the java program and the
operating system.
• Key components in JVM are
• Class loader
• Bytecode verifier
• Just In Time (JIT) compiler

8. How java program is executed?

9. How to compile and run java program
• The java program should be saved with an extension “.java”
• The command to compile the java program is “javac name.java ”
• The command to run the java program is “java name”

10. Sample Java program – Hello World

11. Main Concepts of OOP
• Encapsulation
• Inheritance
• Polymorphism
• Abstraction

12. Encapsulation
• Encapsulation is the technique of making the fields in a class private
and providing access to the fields via public methods.
• The main benefit of encapsulation is the ability to modify our
implemented code without breaking the code of others who use our
code.
• Encapsulation gives maintainability, flexibility and extensibility to our
code.

13. Access Specifiers in java
• public
• private
• protected
• Default

14. Public access specifier
• A class, method, constructor, interface etc., declared public can be
accessed from any other class.
• Therefore fields, methods, blocks declared inside a public class can be
accessed from any class belonging to the Java Universe.
• If the public class we are trying to access is in a different package,
then the public class still need to be imported.

15. Private access specifiers
• Methods, Variables and Constructors that are declared private can
only be accessed within the declared class itself.
• Private access modifier is the most restrictive access level. Class and
interfaces cannot be private.
• Variables that are declared private can be accessed outside the class if
public getter methods are present in the class.
• Using the private modifier is the main way that an object
encapsulates itself and hide data from the outside world.

16. Sample code for private access specifier

17. Protected access specifier
• Variables, methods and constructors which are declared protected in
a superclass can be accessed only by the subclasses in other package
or any class within the package of the protected members' class.
• The protected access modifier cannot be applied to class and
interfaces. Methods, fields can be declared protected, however
methods and fields in a interface cannot be declared protected.

18. Sample code for protected access specifier

19. Default specifier
• The default specifier is used to make a class visible to all the other
classes in its package but not visible to classes from other packages

20. Inheritance
• Inheritance is a compile-time mechanism in Java that allows you to
extend a class with another class
• The keyword extends is used for inheriting a Class.
• The class which extends some other class is called as derived class
• The base class is called as the super class or parent class.

21. Types of inheritance
• Simple inheritance
• Multilevel inheritance
• Hierarchical inheritance
• Hybrid inheritance

22. Simple inheritance
• There are only 1 base class and 1 derived class
• Syntax:
Class Parentclass
{
}
Class Dclass extendsParentclass
{
}

23. Simple inheritance sample code and output

24. Multilevel inheritance
• It contains derived classes which are in turn base class to another class.
class Base
{
}
class Derived1 extends Base
{
}
class Derived2 extends Derived1
{
}

25. Multilevel inheritance sample code and
output

26. Hierarchical inheritance
• It contains one base class and more than one derived class.
class Base
{
}
class Derived1 extends Base
{
}
class Derived2 extends Base{ }

27. Sample code and output for Hierarchical
inheritance

28. Hybrid inheritance
• It is a combination of any two or more inheritances.

29. Sample code for hybrid inheritance

30. Interface
• An interface in Java is similar to a class, but the body of an interface
can include only abstract methods and final fields (constants).
• A class implements an interface by providing code for each method
declared by the interface.
• The keyword used in interface concepts are interface and implements

31. Syntax for interface
interface interfacename
{
method_declaration();
}
class A implements interfacename
{
method_declaration(){ }
}

32. Interface sample code

33. Interface sample output

34. Any queries??

35. Thank you 