Java Programing laungage

Core Java Tutorial

Introduction of Core Java

How To Install JDk and Set of Path

Syntax of java Program

Difference between Java and C/C++

Advantage and Disadvantage of Java

What is Java

Why Java is not Pure Object Oriented Language

Java has Following Features/Characteristics

Limitation of Java Language and Java Internet

Common Misconception about Java

Simple Program of Java

Integrated Development Environment in java

Compile and Run Java Program

Applet and Comments in Java

Tokens in Java

Keywords in Java

Identifier and Variables in Java

Literals/Constants

Data Type in Java

Assignments and Initialization in Java

Operators in Java

Rule of Precedence in Java

Operator on Integer and Separators in Java Programming

Java Control Flow of Statements

If and If-else Selection Statement

Nested If-else and If-else-If Selection Statement

switch case and conditional operator Selection Statement

for and while Loop

do..while and for each Loop

break and labeled break statement

continue and labeled continue statement

return Statement and exit() Method

Escape Sequence for Special Characters and Unicode Code

Constants and Block or Scope

Statement in Java

Conversions between Numeric Types in Java

Import Statement in Java

User Input in Java using Scanner Class

User Input in Java using Console Class

Array in Java

One Dimensional Array

Two Dimensional Array

Two Dimensional Array Program

Command Line Argument in Java

String args Types in Java

Uneven/Jagged array in java

Math Class Function and Constant

Math Class all Function used in a program

Enumerated Types in Java

Object Oriented Programming v/s Procedural Programming

Object Oriented Programming Concepts in Java

Introduction to Class,Object and Method in Java

Class Declaration in Java

Class & Objects in java

Encapsulation in Java

Modifiers/Visibility for a Class or Interrface or member of a Class

Polymorphism in Java

Runtime polymorphism (dynamic binding or method overriding)

What are classes and objects in java?
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In object-oriented programming languages like Java, a class is a construct that is used as a template to create objects of that class. This construct describes the state and behaviour that the objects of the class share.

Since in Java we cannot do anything without class, so when we write a source code in java we are actually creating a class but not object. Writing a class is called implementing a class and has two main components :the class declaration and the class body. Class declaration contains name of the class and other attributes like access modifiers, whereas class body consists of various methods, variables, and the logic of the code. The body of a class is contained within the curly{}braces, can be declared as :

access-modifier class ClassName
{
  //some variables
  // methods
 // logic of code
}  

Objects in java are the entities in the real world problem, and are the building blocks of any Java program. Whenever we write a source code, we are writting a class and code for creating the objects from that class. Thus, when a program is running objects are created for doing their specific jobs for which they have been created.

Thus, we can say that a class is a template that we write and objects are created from the class. In technical terms we can say that an object is instantiated from a class and this process is called instantiation, that's why objects are also called the instances of the class.

 

What are main components of a class ?

Every class in Java have the following components :

  • fields: Fields are variables that held data specific to each object. For e.g., a student may have an ID number, also known as member variables.
  • methods: Methods perform operations on an object. For e.g., a student may have to see his/her marks.
  • static fields: Static fields are common to any object of the same class, only one static field exists for one class.
  • static methods :Static methods are methods that do not affect a specific object.
  • nested classes: It is useful to contain a class within another one if it cannot be accessed outside of the class.
  • Java Tutorialsconstructors: It is a special method that generates a new object and have same name as of a class.
Java Tutorialsclass ShowClass
{
private static int i=0; //defined a static field
int j=1;
ShowClass()
{
 //default constructor declaration
}
public static void show()   //defined a static method
{
System.out.println("The value of i is :"+i);
//System.out.println("The value of j is :"+j);         
//this statement will cause compilation  error, since j is non-static
}
public static void main(String args[])
{
ShowClass sc=new ShowClass();
show();                                             
//we don't have to create an object to call a static method
sc.show();
}
} 
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