jvm and oops introduction
DESCRIPTION
Brief Introduction about JVM and OOP'S Concept.TRANSCRIPT
static Keyword :◦ The static keyword is used in java mainly for memory
management.
Types Of Static Members :◦ Java supporting four types of static members
1. static variables2. static blocks3. static methods4. main method
Non-static Members :◦ Class level members which don’t have static keyword in their creation statement are called non-static members.
Types Of Non-static Members :◦ Java supporting four types of non-static members
1. Non-static variables2. Non-static blocks3. Non-static methods4. Constructors
Package:◦ It is a Java folder used to group related classes , interfaces
and enums.
Class :◦ Class is a collection of data members and member functions
Interface :◦ Interface is a fully unimplemented class , it is used for
defining set of object operations.
Abstract Class :◦ A class that is declared with abstract keyword, is known as
abstract class in java
DataType :◦ Data type gives information about size of the memory
location and range of data that can be stored inside that location .
1. Primitive types2. Referenced types
Primitive Types: ◦ Primitive Data types is used to store single value at a time.
Size and Default value of Primitive type:
Data Type Name Size [ byte( s ) ] Default Value
byte 1 0
short 2 0
int 4 0
long 8 0
float 4 0.0
double 8 0.0
char 2 ‘\u0000'
boolean 1 false
Types of Loop :◦Java has very flexible three looping mechanisms.
1. while loop2. do…while3. for loop
Enhanced for Loop : Syntax :
for (data_type variable: array_name){ --------- --------- }
Switch-case:◦ A switch statement allows you to test the value of an
expression and, depending on that value, to jump directly to some location within the switch statement.
Syntax: switch (expression) { case value1: //statement s break; ------------------------ case value n: //statements default: //default statement sequence }
Using String in Switch-case:◦ In Java SE 7 and later, you can use a String object in
the switch statement's expression.
Use of instanceof keyword:◦ The instanceof operator allows you to determine the type of
an object. Example:- if(employee instanceof Person){ --------------------- --------------------- }
Class:oA class can be defined as a template/blue print that describes
the behaviours/states that object of its type support. Syntax to declare a class: class <class_name>{ data member; method; } Object:
◦ object is the physical reality of a class. Object’s characteristics : 1.State 2.Behaviour 3.Identity
Relationship with Objects:◦ Java supports three types of relationship:
1.IS-A.(Inheritance) 2.HAS-A.(Composition) 3.USES-A.(Aggregation)
OOPs Features:◦ We have mainly four OOPs Features:
1.Encapsulation 2. Inheritance 3. Abstraction
4. Polymorphism
Encapsulation:◦ The process of creating a class by Hiding internal data from
the outside.
Inheritance:◦ The process of creating a class to reuse exited class member
using our class name or objects is called inheritance.
Abstraction :◦ The process of defining a class by providing necessary
details to class objects operation by hiding or removing its implementation details called abstraction.
Polymorphism:◦ The process of defining a class by with multiple methods
with same name but different implementation is called polymorphism.
Types of Polymorphism: 1. Compile-time polymorphism.
2. Run-time polymorphism.
Behaviors of Polymorphism: ◦ we can developed polymorphism by using
1. Method Overloading. 2. Method Overriding
Return Type Declaration:◦ Use the return statement to return the value.◦ Declare a method's return type in its method declaration. ◦ Declare Within the body of the method.
Types Of Constructor:◦ Default constructor (no-argument constructor):
A constructor that have no parameters Ex-
◦ Parameterized constructor: A constructor that have parameters
Constructor Overloading:◦ A class can have any number of constructors that differ in
parameter lists. Constructor Chaining:
◦ Calling one constructor from other.
this Keyword:◦ this is a reference variable that refers to the current object.
super Keyword :◦ super is a reference variable that is used to refer immediate
parent class object.
Array:◦ Array is a collection of similar type of elements that have
continuous memory location. Array Declaration:
◦ 1 Dimensional Declaration- Ex-int[] x;
◦ 2 Dimensional Declaration- Ex-int[][] x;
Array Initialization :◦ Syntax- Datatype arrayName = new datatype[size];
Array Assignment :◦ Syntax- DataType[] arrayRefVar = {value0, value1, ..., value
k}; Anonymous Array:
◦ Array without any name.◦ Syntax- new datatype[]{10,20,30};