JAVA

 Java is a programming language and a platform. Java is a high level, robust, object-oriented and secure programming language.

Java was developed by Sun Microsystems (which is now the subsidiary of Oracle) in the year 1995. James Gosling is known as the father of Java. Before Java, its name was Oak. Since Oak was already a registered company, so James Gosling and his team changed the Oak name to Java.

Platform: Any hardware or software environment in which a program runs, is known as a platform. Since Java has a runtime environment (JRE) and API, it is called a platform.

Java Platforms / Editions

There are 4 platforms or editions of Java:

1) Java SE (Java Standard Edition)

2) Java EE (Java Enterprise Edition)

3) Java ME (Java Micro Edition)

4) JavaFX

Features of Java

Simple

Object-Oriented

Portable

Platform independent

Secured

Robust

Architecture neutral

Interpreted

High Performance

Multithreaded

Distributed

Dynamic

Token

Smallest individual unit in a java program is known as Token.

1.keywords(Reserved Words)

2.Identifiers (variables)

3.Literals(Constant)

4.Operators

5.Symbols

Java Keywords

Java keywords are also known as reserved words. Keywords are particular words which acts as a key to a code. These are predefined words by Java so it cannot be used as a variable or object name.

eg:abstract

assert (since Java 1.4)

boolean

break

byte

case

catch

char

class

const (not used)

continue

default

do

double

else

enum (since Java 5.0)

extends

final

finally

float

for

goto (not used)

if

implements

import

instanceof

int

interface

long

native

new

package

private

protected

public

return

short

static

strictfp (since Java 1.2)

super

switch

synchronized

this

throw

throws

transient

try

void

volatile

while

Java Variables

A variable is a container which holds the value while the Java program is executed. A variable is assigned with a data type.

Variable is a name of memory location. There are three types of variables in java: local, instance and static.

There are two types of data types in Java: primitive and non-primitive.

Variable is name of reserved area allocated in memory. In other words, it is a name of memory location. It is a combination of "vary + able" that means its value can be changed.

Types of Variables

There are three types of variables in Java:

local variable

instance variable

static variable

Constants:  Cannot alter its value during execution of program.

Operators :Operator in Java is a symbol which is used to perform operations.

There are many types of operators in Java

Unary Operator,

Arithmetic Operator,

Shift Operator,

Relational Operator,

Bitwise Operator,

Logical Operator,

Ternary Operator and

Assignment Operator.

Punchuators:

, ; : ( ) [ ] { }

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Java is an object-oriented programming language. Everything in Java is an object. Object-oriented means we organize our software as a combination of different types of objects that incorporates both data and behavior.

Object-oriented programming (OOPs) is a methodology that simplifies software development and maintenance by providing some rules.

Basic concepts of OOPs are:

Object

Class

Inheritance

Polymorphism

Abstraction

Encapsulation

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public class FIRST {

public static void main(String[] args) {

// TODO Auto-generated method stub

System.out.println("HARISREE GANAPATHAYEE NAMA");

}

}

===============================================

public class FIRST {

public static void main(String[] args) {

// TODO Auto-generated method stub

int a=10;

int b=5;

int c=a+b;

System.out.println(c);

}

}

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Java Variables

A variable is a container which holds the value while the Java program is executed. A variable is assigned with a data type.

Variable is a name of memory location. There are three types of variables in java: local, instance and static.

There are two types of data types in Java: primitive and non-primitive.

Variable is name of reserved area allocated in memory. In other words, it is a name of memory location. It is a combination of "vary + able" that means its value can be changed.

Types of Variables

There are three types of variables in Java:

local variable

instance variable

static variable

Data Types in Java

Data types specify the different sizes and values that can be stored in the variable. There are two types of data types in Java:

Primitive data types: The primitive data types include boolean, char, byte, short, int, long, float and double.

Non-primitive data types: The non-primitive data types include Classes, Interfaces, and Arrays.

Java Primitive Data Types

In Java language, primitive data types are the building blocks of data manipulation. These are the most basic data types available in Java language.

There are 8 types of primitive data types:

boolean data type

byte data type

char data type

short data type

int data type

long data type

float data type

double data type

Operators in Java

Operator in Java is a symbol which is used to perform operations. For example: +, -, *, / etc.

There are many types of operators in Java

Unary Operator,

Arithmetic Operator,

Shift Operator,

Relational Operator,

Bitwise Operator,

Logical Operator,

Ternary Operator and

Assignment Operator.

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int x=10;  

System.out.println(x++);//10 (11)  

System.out.println(++x);//12  

System.out.println(x--);//12 (11)  

System.out.println(--x);//10

=================================

int a=10;  

int b=10;  

System.out.println(a++ + ++a);//10+12=22  

System.out.println(b++ + b++);//10+11=21

===============================================

Java Unary Operator Example: ~ and !

int a=10;  

int b=-10;  

boolean c=true;  

boolean d=false;  

System.out.println(~a);//-11 (minus of total positive value which starts from 0)  

System.out.println(~b);//9 (positive of total minus, positive starts from 0)  

System.out.println(!c);//false (opposite of boolean value)  

System.out.println(!d);//true 

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Java Arithmetic Operator Example

int a=10;  

int b=5;  

System.out.println(a+b);//15  

System.out.println(a-b);//5  

System.out.println(a*b);//50  

System.out.println(a/b);//2  

System.out.println(a%b);//0 

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Java AND Operator Example: Logical && and Bitwise &

int a=10;  

int b=5;  

int c=20;  

System.out.println(a<b&&a<c);//false && true = false  

System.out.println(a<b&a<c);//false & true = false  

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Java Assignment Operator Example

int a=10;  

int b=20;  

a+=4;//a=a+4 (a=10+4)  

b-=4;//b=b-4 (b=20-4)  

System.out.println(a);  

System.out.println(b);  

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