Unit1 introduction to Java

 Java is one of the world's most important and widely used
computer languages, and it has held this distinction for
many years.
 Java is Object oriented programming language.
 Helps to create modular programs and reusable code.
 Java is free to access and can run on all platforms.
 Java was developed by James Gosling, Patrick Naughton,
Mike Sheridan at Sun Microsystems Inc. in 1991.
 The initial name was Oak but it was renamed to Java in
1995 as OAK was a registered trademark of another Tech
company.
Overview Of Java

 Java was initially launched as Java 1.0 but soon after its initial
release, Java 1.1 was launched. Java 1.1 redefined event
handling, new library elements were added.
 In Java 1.2 Swing and Collection framework was added
and suspend(), resume() and stop()methods were deprecated
from Thread class
 JAVA EDITIONS.
 J2SE(Java 2 Standard Edition) - to develop client-side
standalone applications or applets.
 J2ME(Java 2 Micro Edition ) - to develop applications for
mobile devices such as cell phones.
 J2EE(Java 2 Enterprise Edition ) - to develop server-side
applications such as Java servlets and Java ServerPages.
Evolution Of Java

.
 Java is widely used in every corner of world and of human life
 Java is not only used in softwares but is also widely used in
designing hardware controlling software components.
 Banking: To deal with transaction management.
 Retail: Billing applications that you see in a store/restaurant are
completely written in Java.
 Information Technology: Java is designed to solve
implementation dependencies.
 Android: Applications are either written in Java or use Java API.
Financial services: It is used in server-side applications.
 Stock market: To write algorithms as to which company they
should invest in.
 Big Data: Hadoop MapReduce framework is written using Java.
 Scientific and Research Community.
Application of Java

 Developing Desktop Applications
 Web Applications like Linkedin.com,
Snapdeal.com etc
 Mobile Operating System like Android
 Embedded Systems
 Robotics and games etc.
Cont..

 Java is easy to learn and its syntax is quite simple, clean and
easy to understand.
 The confusing and ambiguous concepts of C++ are either left
out in Java or they have been re-implemented in a cleaner
way.
 It is an evolving language
 Does not have complex features as other programming
languages like
 Operator overloading,
 Multiple inheritance through classes, pointers and
 Explicit memory allocation.
Simple

 In java everything is Object which has some
state and behaviour.
 Java can be easily extended as it is based on
Object Model.
 Object oriented programming is a
methododoly in which programs are
organized as collection of objects, each of
which represents an instance of a class
Object Oriented

 Two main problems which cause program failures
i.e memory management mistakes and
mishandled runtime errors can be overcome.
 Memory management mistakes can be overcome by
garbage collection. Garbage collection is automatic de-
allocation of objects which are no longer needed.
 Mishandled runtime errors are resolved by Exception
Handling procedures.
 Java eliminates error prone codes by checking the code at
compile time and runtime .
Robust

Portable
 Unlike other programming languages such as
C, C++ etc which are compiled into platform
specific machines.
 Java is write-once, run-anywhere language-
compiled version of class can run on any
platform.
Platform Independent

 When it comes to security, Java is always the first choice.
With java secure features it enable us to develop virus
free, temper free system.
 Java program always runs in Java virtual machine
environment with almost null interaction with system OS,
hence it is more secure.
 Provides a virtual firewall between the application and
the computer.
 Java codes are confined within Java Runtime
Environment (JRE).
 No use of explicit pointers.
Secure

 Java multithreading feature makes it possible to
write program that can do many tasks
simultaneously. Benefit of multithreading is
that it utilizes same memory and other
resources to execute multiple threads at the
same time, like While typing, grammatical
errors are checked along.
Multi Threading

 Compiler generates bytecodes, which have
nothing to do with a particular computer
architecture, hence a Java program is easy to
intrepret on any machine.
 Once compiled Java class file can run on any
platform
Architectural Neutral

JAVA COMPILER
JAVA BYTE CODE
JAVA INTERPRETER
Macintosh Solaris Windows Vista
(translator)
(same for all platforms)
(one for each different system)
Windows 7

 Java Byte code can be carried to any platform.
No implementation dependent features.
 Everything related to storage is predefined,
example: size of primitive data types
 Byte codes are interpeted by JVM
Portable

 Java is an interpreted language, so it will never
be as fast as a compiled language like C or C++.
But, Java enables high performance with the
use of just-in-time compiler.
High Performance

 C is a structured language and Java is an object
oriented language and has mechanism to define
classes and objects.
 Java does not support an explicit pointer type
 Java does not have preprocessor, so we cant use
#define, #include and #ifdef statements.
 Java does not include structures, unions and enum
data types.
 Java does not include keywords like goto, sizeof and
typedef.
 Java adds labeled break and continue statements.
C Language and Java Compared

 Java does not support operator over loading.
 Java does not perform automatic type conversions that
result in loss of precision.
 Java does not support global variables. Every method and
variable is declared within a class and forms part of that
class.
 Java does not allow default arguments.
 Java does not support inheritance of multiple super classes
by a sub class (i.e., multiple inheritance). This is
accomplished by using “interface” concept.
 It is not possible to declare unsigned integers in java.
 In java objects are passed by reference only. In C++ objects
may be passed by value or reference.
C++ and Java Compared

 Multithreading, that allows two or more pieces of the same
program to execute concurrently.
 C++ has a set of library functions that use a common header file.
But java replaces it with its own set of API classes.
 It adds packages and interfaces.
 Java supports automatic garbage collection.
 break and continue statements have been enhanced in java to
accept labels as targets.
 The use of unicode characters ensures portability.
NEW FEATURES ADDED IN
JAVA

Java Runtime Environment
 JRE : The Java Runtime Environment (JRE) provides the
libraries, the Java Virtual Machine, and other components
to run applets and applications written in the Java
programming language.
 JRE does not contain tools and utilities such as compilers
or debuggers for developing applets and applications.
 JRM=JVM+ set of libraries+ other additional fies

Java Development Kit
 JDK : The JDK also called Java Development
Kit is a superset of the JRE, and contains
everything that is in the JRE, plus tools such as
the compilers and debuggers necessary for
developing applets and applications.
 JDK=JRE+ Development tools

 Java virtual Machine(JVM) is a virtual Machine that provides
runtime environment to execute java byte code.
 The JVM doesn't understand Java pogram, that's why you
compile your *.java files to obtain *.class files that contain the
bytecodes understandable by the JVM.
 JVM control execution of every Java program. It enables features
such as automated exception handling, Garbage-collected heap.
What is JVM?

 Class Loader : Class loader loads the Class for execution.
 Method area : Stores pre-class structure as constant pool.
 Heap : Heap is in which objects are allocated.
 Stack : Local variables and partial results are store here. Each
thread has a private JVM stack created when the thread is
created.
 Program register : Program register holds the address of JVM
instruction currently being executed.
Conti..

 Native method stack : It contains all native used in
application.
 Executive Engine : Execution engine controls the
execute of instructions contained in the methods of
the classes.
 Native Method Interface : Native method interface
gives an interface between java code and native code
during execution.
 Native Method Libraries : Native Libraries consist
of files required for the execution of native code.
Conti..

 Object
 Class
 Inheritance
 Polymorphism
 Abstraction
 Encapulation
Object Oriented Concepts

 Abstraction
 Denotes the extraction of essential characteristics of an object that distinguish from all
other kinds of objects.
 Encapsulation
 Hiding the implementation details of a class.
 Forces the user to use an interface to access the data.
 Inheritance
 Process by which one class acquires the properties and functionalities of the other.
 Polymorphism
 Means the ability of methods to exist in several different forms
Object Oriented Programming

Object
31
 Objects are the basic run time entities in an object oriented system.
They may represent a person, a place, a bank account, a table of
data or any item that the program has to handle.
 Objects have two characteristics: They have states and behaviors.
 Object: Car
State: Color, Brand, Model
Behavior: Accelerate, Slow Down, Gear change.
What is the state and behavior of this bulb?

A bulb:
1. It’s a real-world thing.
2. Can be switched on to generate light and switched off.
3. It has real features like the glass covering, filament and holder.
4. It also has conceptual features like power.
5. A bulb manufacturing factory produces many bulbs based on a basic
description / pattern of what a bulb is.
object
methods
member variables
class
Putting it together
32

Class
33
 A class is a construct created in object-oriented programming
languages that enables creation of objects.
 Also sometimes called blueprint or template or prototype
from which objects are created.
 It defines members (variables and methods).
 Characteristics of an object are represented in a class as
Properties/state/variables. The actions that can be performed
by objects become functions of the class and is referred to as
Methods/behaviour.
 A class is an abstraction.

class <ClassName>
{
attributes/variables;
Constructors();
methods();
}
Class syntax

Abstraction
35
 Abstraction refers to the act of representing essential features
without including the background details or explanations.
 Example
 For a Doctor you are a Patient
 Name, Age, Old medical records
 For a Teacher you are a Student
 Name, Roll Number/RegNo, Education background
 For HR Staff you are ______________
 ___________,_____________,___________
Abstraction denotes essential characteristics of an object that
distinguish it from all other kinds of objects and thus provide crisply
defined conceptual boundaries, relative to the perspective of the
viewer.
-Grady Booch

Encapsulation
36
 Encapsulation is binding data and operations that work on data
together in a construct.
 Encapsulation involves Data and Implementation Hiding.
Would you like it if your CPU is given
to you like this?
What are the problems if it were given
to you like this?
Encapsulation is the process of compartmentalizing the elements of
abstraction that constitute its structure and behavior; encapsulation
serves to separate the contractual interface of an abstraction and its
implementation.
- Grady Booch

Class and Encapsulation
Student
•-roll: long
• -name: String
• + display(): void
• + read(): boolean
Rectangle
• -length: int
• -width:int
• +area(): int
LinkedList
•-Node
•+ addFirst(Node n)
•+ remove(Node n)
•+ add(Node n, int pos)
- : private
+ : public

Reuse in Object Oriented
Programming
38
 Object Oriented programming also implements reuse in the same
way that we do in real life.
 Using
 has-a
 is-a
 Has-a or composition relationship is implemented by having a
class having another class as its member, or rather an object
having another object as its member.
 Car has a Stereo
 College has Teachers and Students
 Is-a is implemented through what we call inheritance relationship

Inheritance
 Inheritance allows to reuse classes by deriving a new class from
an existing one
 The existing class is called the parent class, or superclass, or base
class
 The derived class is called the child class or subclass. The child
class inherits characteristics of the parent class(i.e the child class
inherits the methods and data defined for the parent class
 Defines IS-A relationship between classes
 Cat IS-A Animal
 Car IS-A Vehicle
 Rose IS-A Flower

Inheritance hierarchy
40
Animal
legs
tail
run()
Dog
bark()
Tiger
growl()
CatFamily
paddedClaws
whiskers
Cat
meow()
Single -level
Multi-level

 Many Object-orientated language does not support this type of
inheritance.
 Java, C# are the examples of object-oriented language that does
not support multiple inheritance through classes.
Mammal Bird
Bat
Multiple inheritance

{ {Super class Subclass
42
 Fruit
 Library
 Cat
 Bird
 Parrot
 Music
 Tiger
 Books
 Apple
 Mango

Activity
 Given the following classes. Can you form inheritance hierarchy?
 Person
 Teacher
 Student
 HOD
 Typist
 Clerk
 What are the common members shared ?

Polymorphism
A concept in type theory, according to which a name (such as a
variable declaration) may denote objects of many different classes
that are related by some common superclass; thus, any object
denoted by this name is able to respond to some common set of
operations in different ways.
- Grady Booch

Polymorphism example
Flower
fragrance()
Rose
fragrance()
Sunflower
fragrance()
FlowerVase
Flower f[]
smell()

 You pick a rose from the vase and smell it?
 What fragrance do you expect?
Flower
fragrance()
Rose
fragrance()
Sunflower
fragrance()
FlowerVase
Flower f[]
smell()
f[0]= rose;
f[1]= sunflower;
….
f[0]. fragrance();
f[1]. fragrance();
…

Benefits of OOP
1. Emphasis is on data rather than procedure.
2. Programs are divided into objects.
3. Methods are reused.
4. Methods that operate on the data of an object are tied together in the data
structure.
5. Data is hidden and can not be accessed by external functions.
6. Objects may communicate with each other through .
7. Good control over data, data of an object can be accessed by methods
associated with the object.
8. Easy to test, upgrade and debug.

 Client-Server Systems(OCSI)
 Object-Oriented Databases(ODBMS)
 Real-Time System Design
 Office Automation Systems
 CAD/CAM Systems
Applications of OOPs

 Object-oriented programming is a method of implementation in which
programs are organized as cooperative collections of objects.
 The object’s state is determined by the value of its properties and its
behavior is determined by the operations that it provides.
 Abstraction is the process of taking only a set of essential characteristics
from something.
 Encapsulation is binding data and operations that work on data together
in a construct.
 Inheritance defines relationship among classes, wherein one class share
structure or behavior defined in one or more classes.
 Polymorphism is using a function in many forms. Poly means ‘many’,
Morphism means ‘forms’.
Summary

Unit1 introduction to Java

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Unit1 introduction to Java