Core-Java-by-Mahika-Tutor.9459891.powerpoint.pptx

mahika.a.motwani@gmail.com
Programming Languages
High Level Languages
(Machine independent)
Low-Level Languages
(Machine dependent)
Assembly
language
Machine(Binary
) language

Java
 Java was created by James Gosling at Sun Microsystems (which is now
acquired by Oracle Corporation) and released in 1995.
 Java is a high level, object-oriented programming language.

Encapsulation
Binding (or wrapping) code and data together into a single unit.
A java class is the example of encapsulation.

Abstraction
Hiding internal details and showing functionality only.
With Abstraction
WithoutAbstractio
n

Inheritance
A mechanism by which a class acquires all the properties and behaviours of
an existing class.
Provides code reusability.
Used to achieve runtime polymorphism.

Polymorphism
Ability to take multiple forms.
Example-
int a=10,b=20,c;
c=a+b; //addition
String firstname=“Sachin”, lastname=“Tendulkar”, fullname;
fullname=firstname+lastname;//concatenation

OOPLs
(Four OOPs features)
Partial OOPL Pure OOPL
Fully OOPL
Classes not mandatory.
Data members and methods can
be given outside class.
e.g. C++
Classes mandatory.
Data members and methods
cannot be given outside class.
e.g. Java
Classes mandatory.
Data members and methods
cannot be given outside class.
Primitive data types not
supported.
e.g. Smalltalk
Java supports primitive data types , hence it is a fully OOPL but not pure
OOPL.
int i=20; //primitive type
Integer a=new Integer(20); //Class type

public static void main(String[] args) {
…………..
…………..
}

returnType
methodName(arguments)
{
……
}
void m1()
{
…..
…..
}
int m2()
{
…..
return 2;
}
int m3(int n)
{
…..
return n*n;
}

class Test
{
public static void myStatic()
{
-----
-----
-----
}
public void myNonStatic()
{
-----
}
}
class Sample
{
public void CallerFunction()
{
// Invoking static function
Test.myStatic();
// Invoking non-static function
Test t= new Test();
t.myNonStatic();
}
}
Invoking Member Funtions Of A Class

class Test
{
public static void main(String[] args)
{
-----
-----
-----
}
}
// Incase of static main()
Test.main();
Invoking main()
Since the main method is static Java virtual Machine can call it without creating
any instance of a class which contains the main method.
// Incase of non-static main()
Test t=new Test()
t.main();

Java Code (.java)
JAVAC
Compiler
Byte Code
(.class)
JVM JVM JVM
Linux Mac Windows

JVM
JVM (Java Virtual Machine) is an abstract machine. It is a
specification that provides runtime environment in which java
bytecode can be executed.
JVM is the engine that drives the java code
The JVM performs following main tasks:
 Loads code
 Verifies code
 Executes code

JRE
 JRE is an acronym for Java Runtime Environment.
JRE
JVM
Llibraries
like rt.jar
Other files

JRE
JVM
Llibraries
like rt.jar
Other files
Development
tools like
javac, java
etc.
JDK
JDK
JDK is an acronym for Java Development Kit.
Includes a complete JRE (Java Runtime Environment) plus tools for developing,
debugging, and monitoring Java applications.

Internal Architecture of JVM
Java
Runtim
e
System
Class Loader
Class
Area
Heap Stack
PC
Registe
r
Native
Method
Stack
Execution
engine
Native
Method
Interface
Java
Native
Libraries
Memory areas
allocated by
JVM

Java Keywords
Words that cannot be used as identifiers in programs.
There are 50 java keywords.
All keywords are in lower-case.
Each keyword has special meaning for the compiler.
Keywords that are not used in Java so far are called reserved
words.

Category Keywords
Access modifiers private, protected, public
Class, method,
variable modifiers
abstract, class, extends, final, implements, interface, native,new, st
atic,
strictfp, synchronized, transient, volatile
Flow control break, case, continue, default, do, else, for, if, instanceof,return, swi
tch,
while
Package control import, package
Primitive types boolean, byte, char, double, float, int, long, short
Exception handling assert, catch, finally, throw, throws, try
Enumeration enum
Others super, this, void
Unused const, goto
Points to remember
 const and goto are resevered words.
 true, false and null are literals, not keywords.
List of Java Keywords

Rules for Naming Java Identifiers
Allowed characters for identifiers are[A-Z], [a-z],[0-9], ‘$‘(dollar sign)
and ‘_‘ (underscore).
Should not start with digits(0-9).
Case-sensitive, like id and ID are different.
Java keyword cannot be used as an identifier.
Java Identifiers
Names given to programming elements like variables,
methods, classes, packages and interfaces.

Java Naming conventions
Name Convention
class name should start with uppercase letter and be a noun e.g.Shape, String, Color, System, Thread
etc.
interface name should start with uppercase letter and be an adjective e.g. Runnable, Clonable etc.
method name should start with lowercase letter and be a verb e.g. compute(), print(), println() etc.
variable name should start with lowercase letter e.g. firstName, lastName etc.
package name should be in lowercase letter e.g. java, lang, sql, util etc.
constants name should be in uppercase letter. e.g. BLUE, MAX_PRIORITY etc.

Class
 A template that describes the data and behavior.
Object
An entity that has state and behavior is known as an object e.g. chair, bike,
table, car etc.
state: represents data (value) of an object.
behavior: represents the functionality of an object such as deposit,
withdraw etc.

Student
Data
members
id
name
Methods
setId()
setName()
getId()
getName()
class

public class Student {
private int id;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
Java class example

Instantiation/ Object Creation-
Classname referenceVariable=new Classname();
e.g.-
Student s=new Student();
Method Invocation/Call-
Non-static method:
referenceVariable.methodname();
e.g.- s.show();
static method:
Classname.methodname();
e.g.- Sample.display();

Scanner class
A class in java.util package
Used for obtaining the input of the primitive types like int, double etc. and strings
Breaks its input into tokens using a delimiter pattern, which by default matches
whitespace.
To create an object of Scanner class, we usually pass the predefined object System.in,
which represents the standard input stream.
We may pass an object of class File if we want to read input from a file.

Creating instance of Scanner class
To read from System.in:
Scanner sc = new Scanner(System.in);
To read from File:
Scanner sc = new Scanner(new File("myFile"));

Commonly used methods of Scanner class
Method Description
public String next() it returns the next token from the scanner.
public byte nextByte() it scans the next token as a byte.
public short nextShort() it scans the next token as a short value.
public int nextInt() it scans the next token as an int value.
public long nextLong() it scans the next token as a long value.
public float nextFloat() it scans the next token as a float value.
public double nextDouble() it scans the next token as a double value.

Types of Variable
local instance static

public class Student
{
int rn; //instance variable
String name; //instance variable
static String college; //static variable
void m1()
{
int l; //local variable
……
}
……….
}

id=1
name= Hriday
Stack
Heap
id=2
name= Anil
s1
s2
college=“SVC”
”
Class Area
class Student{
int id;
String name;
static String college=“SVC”;
………
public static void main(String args[]){
Student s1=new Student();
Student s2=new Student();
…………
}
}

Core-Java-by-Mahika-Tutor.9459891.powerpoint.pptx

Data Type Default Value Default size
boolean false 1 bit
char 'u0000' 2 byte
byte 0 1 byte
short 0 2 byte
int 0 4 byte
long 0L 8 byte
float 0.0f 4 byte
double 0.0d 8 byte
lowest unicode value:u0000
highest unicode value:uFFFF

Control Structures
1. Conditional
a) Simple if
b) if–else
c) if-else-if ladder
d) Nested if
e) switch case
2. Looping
a) while loop
b) for loop
c) do while loop
d) for each/enhanced for loop

if Statement:
if(condition){
//code to be executed
}

if –else Statement:
if(condition){
//code if condition is true
}
else{
//code if condition is false
}

if-else-if ladder Statement
if(condition1){
//code to be executed if condition1 is true
}
else if(condition2){
}
else if(condition3){
}
...
else{
//code to be executed if all the conditions are false
}
Test
Expression 1
Test
Expression 2
Test
Expression 3
No
No
No
Statement
1
Statement
2
Statement
3
else Body
Yes
Yes
Yes

if(Boolean_expression 1)
{
// Executes when the Boolean expression 1 is true
if(Boolean_expression 2)
{
// Executes when the Boolean expression 2 is true
}
}
Nested if

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