The document discusses key concepts of inheritance, aggregation, encapsulation, overloading, the static keyword, and the 'this' keyword in Java. It explains the mechanisms and relationships (is-a and has-a), the purpose of encapsulation, method overloading, static methods and variables, and the usage of the 'this' reference. Specific examples are provided to illustrate these concepts.

1. P.1
Inheritance
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2. Inheritance in Java P.2
 Is a mechanism in which one acquires all the properties and behavior
of parent object
 You can create new classes that are built upon exist classes
 You can reuse methods and fields of patent class, and add new.
 Inheritance represents the IS-A relationship.
The extends keyword indicates that you are making
a new class that derives from an existing class

3. Inheritance Cont. : P.3
C IS-A D and B IS-A D
class D
class Cclass B
There can be three types of inheritance in Java:
Single, multilevel and hierarchical
Note: Multiple inheritance is not supported in java through class.

4. Example : P.4

5. P.5
Aggregation

6. Aggregation In Java : P.6
 Is class have an entity reference
 Aggregation represents HAS-A relationship

7. Example : P.7

8. P.8
Encapsulation

9. Encapsulation in Java P.9
 Is a process of wrapping code and data together into a single unit.
 We can create a fully encapsulated class in Java by making all the data
member of the class private.
 Now we can use setter and getter methods to set and get the data in it.
 It provides you the control over the data.

10. Class Student : P.10

11. Overloading In Java : P.11
 Is class has multiple methods by same name but different parameters.
 Increases the readability of the program.
There are two ways to overload the method:
1. by changing by of arguments
2. by changing the data type
We can not overloading by changing the return type of the method

12. Overloading Cont. : P.12

13. Overloading Cont. : P.13

14. Overloading Cont. : P.14
One type is promoted to another implicitly if no matching datatype is found

15. cdf
Java static keyword: P.15
 Is used for memory management mainly.
 Variable , methods, blocks and nested class.
Static variable :
If you declare any variable as static, it is know static variable.
• Can be used to refer the common property of all object.
• Gets memory only once in class area at the time of class loading.
s1
s2
num=1
fullname=“Maala:
num=2
fullname=“Elian”
college=“IT”
Stack memory
Heap memory

16. Example 1: P.16

17. Example 2: P.17

18. Static method: P.18
Apply static keyword with any method.
 belongs to the class rather than object of a class.
 Can be invoked without the need for creating an instance of a class.
 Can access static data member and can change the value of it.

19. Example 1: P.19
P.S:
1. The static method can not use non static data member
or call non static method directly.
2. This and super cannot be used in static context.

20. Static block P.20
 Is used to initialize the static data member.
 It is executed before main at the time of class loading.
P.S:
You can execute a program without main() method, with static block but
In previous version of JDK not in JDK 1.7

21. Java this keyword: P.21
this is a reference variable that refer to the current object.
a.) can be used to refer current class instance variable.

22. this keyword Cont. : P.22
b.) this() can be used to invoked current class constructor:

23. P.23
c.) you can used this() constructor call:
this keyword Cont. :
Call to this() must be the first
statement in constructor

24. P.24
d.) this keyword can be used to invoke current class method (implicitly)
this keyword Cont. :

25. P.25this keyword Cont. :
e.) this keyword can be passed as an argument in the method:

26. The End
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