JAVA_Chapter1_ JAVA FUNDAMENTALS, DATA TYPES, OPERATORS & CONTROL STATEMENTS

1.1 History and Philosophy of Java

History

• Developed by Sun Microsystems
• James Gosling is known as father of Java
• Originally called Oak
• Later renamed Java

Philosophy / Features of Java

Feature	Meaning
Simple	easy syntax
Object Oriented	based on objects/classes
Platform Independent	runs anywhere
Secure	no pointer access
Robust	strong memory management
Multithreaded	multiple tasks simultaneously
Distributed	network support
Portable	machine independent
Dynamic	runtime loading

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1.2 Object Oriented Programming (OOP)

OOP Principles

1. Class

Blueprint/template.

class Car{}

2. Object

Real instance of class.

Car c = new Car();

3. Encapsulation

Wrapping data and methods together.

class A{
   private int x;
}

4. Inheritance

Acquire properties from parent class.

class B extends A{}

5. Polymorphism

One thing many forms.

A obj = new B();

6. Abstraction

Hide implementation details.

Using:

• abstract class
• interface

Advantages of OOP

• Code reusability
• Security
• Easy maintenance
• Real-world modeling
• Flexibility

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1.3 Java Development Kit (JDK)

JDK Components

Component	Work
javac	compiler
java	interpreter
javadoc	documentation
JVM	executes bytecode

JVM, JRE, JDK Difference

JVM	JRE	JDK
Executes bytecode	JVM + libraries	JRE + tools

Java Program Execution Process

Source Code (.java)
        ↓
Compiler (javac)
        ↓
Bytecode (.class)
        ↓
JVM
        ↓
Output

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1.4 First Simple Java Program

class Hello{
   public static void main(String args[]){
      System.out.println("Hello");
   }
}

Important Keywords

Keyword	Meaning
class	defines class
public	accessible everywhere
static	no object needed
void	returns nothing
main	starting point
String args[]	command line arguments

Compilation

javac Hello.java

Execution

java Hello

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1.5 Packages in Java

Package

Collection of related classes.

package mypack;

Types of Package

1. Built-in package
2. User-defined package

Important Packages

Package	Use
java.lang	basic classes
java.util	Scanner, collections
java.io	file handling
java.sql	JDBC
javax.swing	GUI

Import Statement

import java.util.Scanner;

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1.6 Java Data Types

Primitive Data Types

Type	Size	Example
byte	8 bit	10
short	16 bit	20
int	32 bit	100
long	64 bit	1000L
float	32 bit	2.5f
double	64 bit	5.67
char	16 bit	'A'
boolean	true/false	true

Non Primitive Types

• String
• Array
• Class
• Interface

Integer Types

int x = 10;
long y = 1000L;

Floating Types

float a = 5.6f;
double b = 9.87;

Character Type

char ch = 'A';

ASCII/Unicode supported.

Boolean Type

boolean flag = true;

String

String s = "Java";

Important String Methods

Method	Work
length()	size
charAt()	character
toUpperCase()	uppercase
equals()	compare

Arrays

Declaration

int a[];

Creation

a = new int[5];

Initialization

int a[] = {1,2,3};

---

1.7 Literals

Fixed values in program.

10
'A'
true
"Hello"

Hexadecimal

int x = 0x12;

Octal

int x = 012;

Binary

int x = 0b1010;

Escape Sequences

Escape	Meaning
\n	newline
\t	tab
\\	backslash
\"	double quote

String Literal

String s = "Hello";

Stored in string pool.

---

1.8 Variables and Constants

Variable

int x = 10;

Types of Variables

Type	Meaning
local	inside method
instance	inside class
static	shared

Constant

final int MAX = 100;

Cannot change.

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1.9 Operators

Arithmetic Operators

+ - * / %

Unary Operators

++
--

Relational Operators

>
<
>=
<=
==
!=

Return boolean.

Logical Operators

&&
||
!

Bitwise Operators

&
|
^
~
<<
>>

Assignment Operators

=
+=
-=
*=

Ternary Operator

x>y ? x : y;

Operator Precedence

() highest
* / %
+ -
= lowest

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1.10 Type Casting

Widening Casting

Automatic.

int x = 10;
double y = x;

Narrowing Casting

Manual.

double x = 9.8;
int y = (int)x;

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1.11 Control Statements

if Statement

if(condition){
}

if else

if(a>b){
}
else{
}

else if Ladder

if(){
}
else if(){
}
else{
}

switch Statement

switch(choice){
   case 1:
      break;
   default:
}

Loop Statements

for loop

for(int i=0;i<5;i++)

while loop

while(condition)

do while loop

do{
}while(condition);

Runs at least once.

break Statement

Terminates loop.

break;

continue Statement

Skips current iteration.

continue;

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Important Practical Programs

1. Sum of two numbers
2. Odd/even check
3. Largest among 3 numbers
4. Factorial
5. Fibonacci series
6. Prime number
7. Palindrome
8. Array sorting
9. Matrix addition
10. String reverse

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MOST IMPORTANT EXAM QUESTIONS

• Features of Java
• Difference between C++ and Java
• JVM vs JRE vs JDK
• Primitive vs non-primitive datatype
• Array vs String
• break vs continue
• while vs do while
• switch vs if else

---

Important Viva

Why Java is platform independent?

Because bytecode runs on JVM.

Why String is not primitive?

Because it is a class/object.

Difference between == and equals()

==	equals()
compares reference	compares content

Difference between compile time and runtime error

Compile Time	Runtime
syntax error	occurs during execution

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