3. Outline
INTRODUCTION
PRINCIPLES OF OBJECT-ORIENTED LANGUAGES
Classes
Objects
Abstraction
Inheritance
Encapsulation
Polymorphism
JAVA ESSENTIALS
JAVA VIRTUAL MACHINE
JAVA FEATURES
BASIC CONSTRUCT/ NOTIONS
Constant , Variable and Data types, Operators and expression
Revision of Branching and looing
4. INTRODUCTION
What Is Object Oriented Programming ?
Object-oriented programming (OOP) is a computer programming
model that organizes software design around data, or objects, rather
than functions and logic.
OR
Object-oriented programming is a method of implementation in which
programs are organized as cooperative collections of objects, each of
which represents an instance of some class, and whose classes are all
members of a hierarchy of classes united via inheritance relationships.
- Grady Booch
6. What Is Object ?
An object is a real-world entity that has attributes, behavior, and
properties. It is referred to as an instance of the class.
It contains member functions, variables that we have defined in
the class.
It occupies space in the memory.
Different objects have different states or attributes, and behaviors.
Object 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.
7. Attributes :
Every object has some attribute different types of
objects contain different attributes or characteristics.
Example
The student are name, roll number , subject The attribute for car
would be color, engine power , number of seats etc.
Attribute are real world are like data they have some
specific value Raj(for name) or 23 (roll number).
8. Behavior :
Behavior defines what can be done with the objects and may manipulate
the attributes of an object
Example,
if a manager orders an employee to do some task, then he responds either
by doing it or not doing it.
The wings of a fan start moving only when the fan is switched ON.
Behavior actually determines the way an object interacts with other
objects.
12. Putting it together
A bulb:
It’s a real-world thing.
Can be switched on to generate light and switched off
It has real features like the glass covering, filament and holder.
It also has conceptual features like power.
A bulb manufacturing factory produces many bulbs based on a basic
description / pattern of what a bulb is.
Object
Methods
member variables
class
13.
14.
15. What is Class ?
A class is a Prototype Or Template or a blueprint of an object.
A class is specification, common to all objects of a particular type.
This specification contains the details of the data and functions that
act upon the data.(Data + Function).
Object of a class are called individual instance of that class.
Any number of objects can be created based on class.
Classes are user defined data types and behaves like the built in
type of a programming language.
16.
17. A class Is defined by 3 element
A unique class name
Data members or attributes
Member functions or methods
22. Now this is just template,
Called as “Class”, and
object is instance of
class
23.
24. Abstraction
Abstraction is a process of hiding the implementation details and showing
only functionality to the user.
For example, when we are driving a car, we are only concerned about
driving the car like start/stop the car, accelerate/ break, etc. We are not
concerned about how the actual start/stop mechanism or
accelerate/brake process works internally. We are just not interested in
those details.
Abstraction reduces the programming efforts and thereby the complexity.
An end-user using the application need not be concerned about how a
particular feature is implemented. He/she can just use the features as
required.
25. Abstraction
In abstraction, we deal with ideas and not the events. This means that we
hide the implementation details from the user and expose only the
functionality to the end-user. Thereby the user will only know “what it does”
rather than “how it does”.
Java provides a non-access modifier “abstract” for implementing
abstraction. This abstract modifier can be used with classes and methods
but not variables.
The interface provides complete abstraction i.e. it only provides method
prototypes and not their implementation.
26. Abstraction in OOP can be of two types.
Data Abstraction
In data abstraction, we mostly create complex data types and hide their
implementation. We only expose the operations to manipulate these data types
without going into the details of their implementation.
One advantage of this approach is that we can change the implementation
anytime without changing the behavior that is exposed to the user.
Control Abstraction
Control abstraction collects all the control statements that are a part of the
application and exposes them as a unit. This feature is used when we have to
perform a working feature using this control unit.
27. Abstraction Example
Let’s first take ATM machine as a
real-time example. We all use an
ATM machine for cash
withdrawal, money transfer,
retrieve min-statement, etc. in
our daily life.
But we don’t know internally
what things are happening
inside ATM machine when you
insert an ATM card for
performing any kind of
operation.
28. Abstraction Example
A car owner knows how to drive
it. He knows about various
components of car and how to
use them.
For example, a car owner knows
that the accelerator pedal is
used to increase the speed of
car, and pressing the brake
pedal stops it.
To perform these simple actions,
you only need to know how to
use these components but not
need to know how they function.
29. Abstraction Example
When you need to send SMS
from your mobile, you only type
the text and send the message.
But you don’t know the internal
processing of the message
delivery.
30. Inheritance
Inheritance is the process by which objects of one class
acquire the properties of objects of another class.
It supports the concept of hierarchical classification.
Inheritance is a compile-time mechanism in Java that
allows you to extend a class (called the that allows you
to extend a class (called the base class or superclass)
with another class (called the derived class or subclass)
or
31. Inheritance
The mechanism of deriving a class from another existing class is called as
inheritance .
Access specifies:- public, protected ,private, default.
34. Encapsulation
Encapsulation is one of the features of object-oriented methodology. The
process of binding the data procedures into objects to hide them from the
outside world is called encapsulation
In other words, encapsulation is a programming technique that binds the
class members (variables and methods) together and prevents them from
being accessed by other classes.
Thereby, we can keep variables and methods safes from outside
interference and misuse.
Every Java class is an example of encapsulation because we write
everything within the class only that binds variables and methods together
and hides their complexity from other classes.
35. Encapsulation Example
Example of encapsulation is a
capsule. Basically, capsule
encapsulates several
combinations of medicine.
If combinations of medicine
are variables and methods
then the capsule will act as a
class and the whole process is
called Encapsulation as shown
in the figure.
36. Real-time Example of Encapsulation in Java
School bag is one of the most real examples of Encapsulation. School bag can
keep our books, pens, etc.
When you log into your email accounts such as Gmail, Yahoo Mail, or Rediff
mail, there is a lot of internal processes taking place in the backend and you
have no control over it.
Suppose you have an account in the bank. If your balance variable is declared
as a public variable in the bank software, your account balance will be known
as public, In this case, anyone can know your account balance. So, would you
like it? Obviously No.
38. Polymorphism
The word polymorphism is derived from two Greek words: poly and
morphs. The word “poly” implies many and “morphs” means forms.
Therefore, polymorphism means “many forms”. That is one thing that
can take many forms.
Polymorphism is a concept by which we can perform a single task in
different ways. That is, when a single entity behaves differently in
different cases, it is called polymorphism in Java.
39. Real-time Example of Polymorphism in Java
1.We all know that water is a liquid,
but it changes to solid when it frozen,
and it changes to a gas when it is
heated at its boiling point.
2. The best example of polymorphism
is human behavior. One person can
have different behavior. For
example, a person acts as an
employee in the office, a customer in
the shopping mall, a passenger in
bus/train, a student in school, and a
son at home.
3. We all use a single button to switch
ON and OFF the computer.
40. Features of Java
Platform Independence
Object Oriented
Both Compiled and Interpreted
Java is Robust
JAVA Language Security Features
Java is Multithreaded
Other Features
Automatic Memory Management
Dynamic Binding
41. Platform Independence
Compiler converts source code to bytecode and then the JVM executes
the bytecode generated by the compiler. This bytecode can run on any
platform be it Windows, Linux, or macOS which means if we compile a
program on Windows, then we can run it on Linux and vice versa. Each
operating system has a different JVM, but the output produced by all the
OS is the same after the execution of bytecode. That is why we call java a
platform-independent language.
42. Object Oriented
It is conceived that Java is a pure object-oriented language, meaning that
the outermost level of data structure in Java is the object.
Everything in Java (constants, variables, and methods) are defined inside a
class and accessed through objects.
Java has been developed in a way that it allows the user to not only learn
object-oriented programming but to apply and practice it.
But there are some constraints that violate the purity of Java. It was
designed mainly for OOP, but with some procedural elements. For
example, Java supports primitive data types that are not objects.
43. Both Compiled and Interpreted
Interpretation:
An interpreter reads one line of a program and executes it before going to the next
line.
The line is parsed to its smallest operations, the corresponding machine-level code is
found, and then the instruction is executed.
In interpretation, there are no intermediate steps between writing/modifying the
code and running it. The best part is: debugging is fast. Also, the programs are easily
transportable to other platforms (if an interpreter is available). The drawback is its
slow performance.
44. Both Compiled and Interpreted
Compilation:
The program text file is first converted to native machine code with a program called
a compiler.
A linker may also be required to connect together multiple code files together. The
output of the compiler is an executable code. C and C++ are both compiled
languages.
The compiler can perform certain optimization operations because it looks at the
program as a whole and not line by line.
The disadvantages include slower debugging and reduced portability to other
platforms. The source code must be recompiled on the destination platform.
45. Java is Robust
Java language is robust which means reliable.
It is developed in such a way that it puts a lot of effort into checking
errors as early as possible, that is why the java compiler is able to
detect even those errors that are not easy to detect by another
programming language.
The main features of java that make it robust are garbage
collection, Exception Handling, and memory allocation.
46. JAVA Language Security Features
Java has several language features that protect the integrity of the security
system and prevent several common attacks.
Security Through Definition Java is strict in its definition of the language:
All primitive data types in the language have a specific size.
All operations are defined to be performed in a specific order.
Security Through Lack of Pointer Arithmetic
Java does not have pointer arithmetic, so Java programmers cannot forge a pointer
to memory. All methods and instance variables are referred to with their symbolic
names. Users cannot write a code that interprets system variables or accesses private
information stored in a system.
Security Through Garbage Collection
Garbage collection makes Java programs more secure and robust by automatically
freeing memory, once it is no longer needed.
47. Java is Multithreaded
A thread can be loosely defined as a separate stream of execution that takes
place simultaneously and independent of everything else that might be
happening.
Threads are independent parts of a process that run concurrently. Using
threads, a program cannot hold the CPU for a long duration intentionally (e.g.
infinite loop).
The beauty of multithreading is that the other tasks that are not stuck in the loop
can continue processing without having to wait for the stuck task to finish.
Threads in Java can place locks on shared resources so that while one thread is
using it, no other
thread is allowed to access it. This is achieved with the help of synchronization.
48. Java Programming Constructs
VARIABLES
PRIMITIVE DATA TYPES
IDENTIFIER
Rules for Naming
Keywords
Data Type
OPERATORS
FLOW OF CONTROL
49. VARIABLES
Variable is a symbolic name refer to a memory location used to store
values that can change during the execution of a program. Java declares
its variables in the following manner:
50. PRIMITIVE DATA TYPES
Primitive data types are the basic building
blocks of any programming language.
A primitive data type can have only one
value at a time and is the simplest built-in
form of data within Java.
All variables in Java have to be declared
before they can be used, that is why Java
is termed as a strongly typed language.
There are eight primitive data types in Java,
as follows:
51.
52. IDENTIFIER
Identifiers are names assigned to variables, constants, methods, classes,
packages, and interfaces.
No limit has been specified for the length of a variable name.
Identifiers can have letters, numbers, underscores, and any currency
symbol.
However they may only begin with a letter, underscore, or a dollar sign.
Digits cannot be the first character in an identifier.
53. Rules for Naming
The first character of an identifier must be a letter, an underscore, or a
dollar sign ($).
The subsequent characters can be a letter, an underscore, dollar sign, or a
digit. Note that white spaces are not allowed within identifiers.
Identifiers are case-sensitive. This means that Total Price and total price are
different identifiers.
Do not use Java’s reserved keywords. A few examples of legal and illegal
identifiers are shown below.
54. Naming Convention
Names should be kept according to their usage, as it is meaningful and
easy to remember as shown in Fig
55. Class or Interface Identifiers
Class or interface identifiers begin with a capital letter.
The first alphabet of every internal word is capitalized. All other letters are in
lower case.
Example:
public class MyClass // class identifier: MyClass
interface Calculator; // interface identifier: Calculator
56. Variable or Method Identifiers
Variable or Method Identifiers start with a lower-case letter. The first
alphabet of every internal word is capitalized. All other letters are in lower
case.
example
int totalPay; // variable identifier: totalPay
MyClass.showResult(); // MyClass is the Class Name and showResult()
is a method of MyClass.
57. Constant Identifiers
Constant Identifiers These are specified in upper case. Underscores are
used to separate internal words.
example
final double TAX_RATE = 0.05; // constant identifier: TAX_RATE
58. Package Identifiers
Package Identifiers These consist of all lower-case letters.
package mypackage.subpackage.subpackage; //Package Declaration
59. Keywords
Keywords are predefined identifiers meant for a specific purpose and
cannot be used for identifying used defined classes, variables, methods,
packages, and interfaces.
All keywords are in lower case.
62. FLOW OF CONTROL
Control flow statements help programmers make decisions about which
statements to execute and to change the flow of execution in a program.
The four categories of control flow statements available in Java are
conditional statement, loops, exception, and branch.
64. Loops
The purpose of loop statements is to execute Java statements many times.
There are three types of loops in Java—
for
while
do ..while
65. for loop
The for loop groups the following three common parts together into one
statement:
(a) Initialization
(b) Condition
(c) Increment or decrement
To execute a code for a known
number of times, for loop is the
right choice.
Syntax
Example
A for loop is useful when you know the exact number of iterations.
66. while Loop
The while loop is used to repeatedly execute a block of statements based
on a condition.
If you want to execute some statements for an indefinite number of times (i.e., number of iterations is unknown), a
while loop may be the better choice.
Example
67. do-while Loop
A do-while loop is also used to repeatedly execute (iterate) a block of
statements. But, in a do-while loop the condition is evaluated at the end of
the iteration. So the do-while loop (unlike the while loop) will execute at
least once and after that depending upon the condition.
68. Branching Mechanism
Java does not offer a go to type of statement as in some older languages,
because it leads to unreadable code.
However, Java supports other ways to jump from one statement to another.
Two types of branching statements are available in Java— break and
continue.
69. break Statement
break statement is used in case the user needs to jump out of a loop. A
break statement is used to jump out of a loop when a particular condition
occurs, as shown below:
70. Continue Statement
Situations can occur where you do not want to jump out of a loop, but
simply stop the current iteration and go back to the top and continue with
the next iteration, as shown in the following code.
Output
