Introduction to java

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Introduction to Java
Presented by
Amit Srivastava
Java Duke
Java 6
Mustang
Java is one of the slang terms for coffee
Java 7
Dolphin

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Agenda
1. Java Introduction
2. Java Basics
3. Object Oriented Basics (OO Basics)
4. Using Constructor and Finalize
5. IS-A and HAS-A
6. Polymorphism, Abstract class and interfaces
7. Pass By Value & Pass By Reference
8. All About Static
9. Deep Inside JVM
10. OOAD

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Java Introduction
 What is Java
 Java History
 WORA
 Java Kick Start
 The way Java Works
 Writing First Java Program

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The Power of Java
Java software powers the onboard computers in toys, cars, planes, rockets, and
even the NASA (National Aeronautics and Space Administration/Agency )
Mars Rover. It brings interactivity to the Internet, real-time graphics to television,
instant imaging to cameras, and multi-player games to mobile phones and
desktop PCs. It connects the largest enterprises and smallest businesses to
their employees, customers, and data. And it secures the vast majority of
electronic transactions in retail, finance, government, science, and medicine. In
short, Java technology goes everywhere you go

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A Mars rover is an automated
motor vehicle which propels itself
across the surface of the planet
Mars after landing.
Rovers have several advantages
over stationary landers: they
examine more territory, they can
be directed to interesting features,
they can place themselves in
sunny positions to weather winter
months.

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Java software runs on more types of consumer and embedded devices, smart
cards, ATMs, thin clients, PCs, servers, and mainframes than any other
software.
Today's six million Java developers are one of the largest communities of
software developers.
The Java economy includes 2.5 billion smart cards, 800 million PCs shipped
with Java, 1.85 billion Java Powered phones , and over 180 telecom providers
who deploy Java technology based content/services.
The Power of Java

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 WHAT IS JAVA?
 Object Oriented Programming
 WORA( Write Once Run any where) or Platform Independence
 The Java language was created by James Gosling in June 1991.
 Java Provides development and deployment environment.
 It is similar in syntax to C++
 It is robust provides exception handling , automatic garbage
collection.
 Designed for the distributed environment.
 Supports Multithreading
 Secure ( No Pointer and Byte Code Verifier)
 Architectural Neutral - If a company develops new hardware , it
doesn’t have to make a new software , only JRE needs to be replace
for New platform).
 Open Source
 High Performance (JITc)
Java Introduction

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what is the mean of platform?
Platform consists of the computer hardware(mainly architecture of the
microprocessor) and OS.
Platform=hardware+Operating System
Anything that is platform indepedent can run on any operating system and
hardware.
Java is platform indepedent so java can run on any operating system and
hardware.
Now question is how it is platform independent?
This is because of the magic of Byte Code which is OS indepedent.
When java compiler compile any code then it generate the byte code not the
machine native code(unlike C compiler).Now this byte code need a interpreter to
execute on a machine.
This interpreter is JVM.So JVM read that byte code(that is machine indepedent)
amd execute it. Different JVM is designed for different OS and byte code is able
to run on different OS.

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 JAVA HISTORY
 Green Project (1991) was designed for
hand-held devices and set-top boxes.
(Requirement was the hardware in the consumer devices
was always changing but the same code use on the
different hardware systems)
 It was originally named as Oak but became
unsuccessful, so in 1995, Sun changed its
name to JAVA
 James Gosling's goals were to implement a
virtual machine and a language that had a
familiar C/C++ style of notation. The first
public implementation was Java 1.0 in 1995.
It promised "Write Once, Run Anywhere"
(WORA).
Note : The initial version of Java is so small it
fit in a floppy. Now it of 60+MB.
Java Introduction

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Java Introduction
 JAVA HISTORY continue…

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JDK 1.0.2 JDK 1.1 JDK 1.2 JDK 1.5 JDK 1.6 JDK 1.7
Oak ------ Playground 1.2
Kestrel 1.3
Merlin 1.4
Tiger Mustang Dolphin
250 Classes 500 Classes 2300 Classes 3500 Classes 3793 Classes 4024 Classes
23 Jan 96 19 Feb 97 8 Dec 98 (1.2)
8 May 2000
(1.3)
6 Feb 2002 (1.4)
30 Sept 2004 11 Dec 2006 28 July 2011
you could use
private and
protected together
to create yet
another form of
protection that
would restrict
access to
methods or
variables solely to
subclasses of a
given class. As of
1.0.2, this
capability has
been removed
from the
language.
Extensive AWT
RMI
Inner Classes
JavaBeans
JDBC
Reflection
JDK 1.2
Strictfp
Swing
CORBA
Collection FW
JDK 1.3
Java Sound
JNDI
Java 1.4
Assert
XML Parser
Security and
Cryptography
Enhance for Loop
Var-Args
Generics
AutoBoxing
Static import
Java Compiler
API
Splash Screen
System Tray Icon
Instrument Class
(For Object Size)
Switch with String
Numeric Literal
with Underscore
Improved
Generics
Catching multiple
Exception
New Java NIO
Java Version Histroy

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JDK 1.8 JDK 1.9 JDK 1.10
Lambda ------
Sept 2013 ---- -----
Improvement in java.lang
package
Parallel Array Sorting
Bulk Data Operations for
Collections
Base64 Encoding and
Decoding
New HTTP Client
More Security
enhancements from the
language
MultiGiga bytes Heap
Self Tuning JVM
Remove Primitive data
types
Move Towards 64 Bit
Addressing

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 WORA
The goal is to write an application which run anywhere.
Java Introduction

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 JAVA KICK START
1. JDK (Java Development Kit)
JDK = javac compiler + .jar (libraries) + javadoc + jdb + JRE
JDK – JDK is a software package which is used to develop and deploy
java applications.
JDK consists
a) javac compiler – it is use to convert .java file into .class file
b) JAR Files - A jar files are java API’s , which contains number of
classes and interfaces. For Example to make a database
connection with oracle we require ojdbc.jar.
c) Javadoc – through this utility we can make Java documentaion for
any java program.
d) Jdb- jdb is a java debugger.
e) JRE – See in the next slide
Java Introduction

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 JAVA KICK START continue…
Java Introduction
2. JRE (Java Runtime Environment)- A JRE is required to run Java
applications interpretively on a target hardware and operating system platform.
JRE=JVM (Java Virtual machine)+ jar files (libraries)
Java Program execution flow

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Java Introduction
3. JVM
JVM is a software that is plat form
specific. For example for Linux
platform
You require a Linux based JVM ,
for windows platform you require a
windows based JVM.
Now in these days JVM is bundled
with Internet explorer and With
other types of browsers.

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A JVM performs the following tasks.
1. Class Loader Load all the .class file, necessary for the execution of
a program.
2. Byte code Verifier It ensures the code does not no illegal data
conversion, no stack over flow, not violate system integrity.
3. JIT – (Just In time compiler) JIT work as a cache for the JVM
interpreted code. It memorized the repeated code instructions (that is
interpreted by the JVM) and when JVM reqiure the same set of
instructions so JIT provides these instructions to the JVM , so JVM
does not interpret the same instructions again
4. Generate Native Code- The JVM and the Java API are built for every
O/S platform. The Java API calls to the O/S API.
Java Introduction

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Java Introduction
In particular, a Java program, unlike one written in C or C++, isn't a
Single executable file, but instead is composed of many individual class files, each
of which corresponds to a single Java class.
Additionally, these class files are not loaded into memory all at once, but rather are
loaded on demand, as needed by the program.
The ClassLoader is the part of the JVM that loads classes into memory.
a) BootStrap or Primordial or Default or System Class Loader – It is a part of the
JVM Implementation. It loads the classes, including the classes of Java API.
b) User-Defined Class Loader- A Java Application can install user-define class
loader that load classes in the custom ways, such as by downloading class files
across a network.
 JAVA Class Loader

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Types of Class Loader in Java
a) BootStrap Class Loader - Bootstrap class loader loads java’s core classes
like java.lang, java.util etc. These are classes that are part of java runtime
environment. Bootstrap class loader is native implementation and so they
may differ across different JVMs. The bootstrap class loader loads the core
Java libraries located in the <JAVA_HOME>/jre/lib directory, search for rt.jar
.
b) Extension Class loader - classes in JAR files in the lib/ext directory of the
JRE, and in the system-wide, platform-specific extension directory (such as
/usr/jdk/packages/lib/ext on the Solaris™ Operating System, but note that
use of this directory applies only to Java™ 6 and later
c) System Class Loader - The class path: classes, including classes in JAR
files, on paths specified by the system property java.class.path. If a JAR file
on the class path has a manifest with the Class-Path attribute, JAR files
specified by the Class-Path attribute will be searched also. By default, the
java.class.path property's value is ., the current directory. You can change
the value by using the -classpath or -cp command-line options, or setting
the CLASSPATH environment variable. The command-line options override
the setting of the CLASSPATH environment variable.

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 The Way Java Works
Java Introduction

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 Writing First Java Program
Step -1 Write Source Code
Example:
class A
{
public static void main(String args[])
{
System.out.println(“Hello Java ! “);
}
}
Step- 2 Save Code with class Name
A.java
Step-3 Compile the code
javac A.java ( when you compile the code it will generate an intermediate code (Byte
code) it is not a machine code.
Step-4 run the Program
java A ( running the program by starting the JVM with the A.class. The JVM translates the
bytecode into something the underlying platform understands , and runs your program.
Execution point of java program
Java Introduction

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System Class
In - System.in
Out - System.out.println()
Err – System.err.println()
Shorten the System.out.println()
Import static java.lang.System.out;
out.println(“Hello Java ! “);

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1. Do you know through System.out.println(), You can write the output in a file
instead of writing on a Console.
2. You can print output in a different language , like in Hindi in Java
3. You can get the Login User Name , Operation System Name, JDK Location,
Number of Processor in a System and many more.
4. Request to the Java Garbage Collector
5. You can not create an object of System class
6. Performance Monitoring of a Method
7. Introduce the printf method
Example:
String name ="Amit";
int age =21;
System.out.printf("Your Name is %s and Age is %d",name,age);
char gender ='M';
System.out.printf("nGender is %c ",gender);
float amount = 12000.50f;
System.out.printf("nAmount is %f",amount);
System.out.printf("nAmount is %6.2f",amount);
The Magic of System class

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Program Observation
When the JVM starts running , it looks for the class that is at the
command line. Then it starts looking for a specially written method that
looks exactly like:
{
//Your Code Here
}
Note: Every Java application has to have at least one class, and at
least one main method.
Java Introduction

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Program Observation continue…
You can define main method in the following ways
a) public static void main(String args[])
b) static public void main(String args[])
c) public static void main(String …a) // Allowed in JDK 1.5 or higher
d) static public void main(String …a) //Allowed in jdk1.5 or higher
The main method is public , because java is package centric language.
Now JVM has to access your main method from outside your package.
That’s why it set to as public
The main method also static , because static is loaded on the compile
Time and not required to instantiate.
The main method is void , because it is not required to return any thing
to the JVM.
Main is the name of the method
String args[] is used for command line arguments , where String is a
Java class.
Java Introduction

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Java Introduction
Program Observation continue…
System.out.println(“Hello Java ! ”);
Where System is a final class, found in java.lang package.
Out is a object of PrintStream class and it declare static in the System
Class.
Println(String msg) this is a method define in the PrintStream class.
Used to print on console and print in new line

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Java Basics
 Identifier
 Variable
 Constant
 Keyword
 Data Types
 Java Coding Conventions
 Sequential Programs
 Conditional Programs
 Looping

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Identifier
It is a name given to a class, variable, constant or method.
Rules for Declaring a Legal Identifier:
a) Identifier must start with a letter, $, _. Cannot start with number.
b) After the first letter, contain numeric.
c) No Limit to the number of characters an identifier can contain.
d) Cannot use keyword in identifier name.
e) Identifiers are case-sensitive.
Java Basics

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Variable
A variable is just like a cup or container. It can hold something.
It has a size and a type.
Example:
int a=123;
a
Java Basics
Sample Example

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 Constant
As the name implies , constants are fixed values which never
change.
Example:
final int MAX=100;
“final” keyword is used to declare a constant in java.
 Keywords
Keywords are reserved which has some special meaning for
the compiler.
For Example : if , while ,int etc.
Java Basics
Sample Example

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 Data types
Variable (Cup) can be of two type
✔Primitive Type
✔Reference Type
Primitive Type – Primitives are like the cups at the Coffee-House
They come in different sizes and each has name like small , big,
medium.
Java Basics

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Primitive Type Example
byte x=10; // Take 1 byte in memory
short y=500; // Take 2 bytes in memory
int a=40000; // Take 4 bytes in memory
Java Basics

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Primitive Data Types List
In Java, primitives come in different sizes with different names.
When you declare a variable in Java, you must declare with a
specific type.
Java Basics
Data Type Bytes Range
boolean
: Internally java treat is 1 for true and 0 for false, and dependent on OS itcan be treated as byte, short, int)
True or false
char 2 Bytes (UNICODE Characters) 0 to 65535
byte 1 byte -128 to 127
short 2 bytes -32768 to 32767
int 4 bytes -2147483648 to2147483647
long 8 bytes huge
float 4 bytes varies
double 8 bytes varies

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TEST YOUR SELF
Java Basics
I am a slow walker, but I never walk back. Said by Abraham Lincoln

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Test Your Self
1. Declare a variable, in which store age of Employee,
choose the best way
a) int age;
b) short age;
c) long age;
d) boolean age;
e) byte age;
2. To declare constant in java
a) const int a=10;
b) int a=10;
c) final int A=10;
d) byte a=10;
3. To store the attendance status of employee , whether Employee is
present or not. Which deceleration is appropriate.
a) boolean att; c) float att;
b) int att; d) double att;
Java Basics

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Test Your Self
4. Which one is the correct variable deceleration ,
choose all that apply
a) int _a;
b) int _____a;
c) int 1a;
d) int emp_no;
e) float @sal;
f) float $sal;
g) double $_bonus;
h) boolean int;
Java Basics

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Reference type
A Reference variable holds bits that represents a way to access
an object.
It doesn't hold the object itself, but it holds something like a
pointer, or an address.
Java Basics

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b
JAVA
Reference Type Example:
String b=”Java”;
Java Basics

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Primitive Type Example
int a=100;
int b=200;
int c=a;
100 200
a b
100
c
Memory Area
Java Basics
Primitive Vs Reference Type

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Java object
reference
World object
reference
Java object
reference
a
b
c
Java
World
Reference Type Example
String a=new String(“Java”);
String b=new String(“World”);
String c=a;
Java Basics
Primitive vs Reference Type

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Using == with primitive type
Example
int a=100;
int b=100;
System.out.println(a==b); //print true
Using == with reference type
Example:
String a=new String(“Hello”);
String b=new String(“Hello”);
System.out.println(a==b); // false But Why ???
Answer is, The reference type checks address in this case , it return true if both
address or references are same.
So HOW I COMPARE VALUES IN REFERENCE TYPE, BECAUSE == CHECKS
ADDRESS NOT VALUE?
Answer is using equals()
System.out.println(a.equals(b)); //return true
Java Basics

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TEST YOUR SELF
Java Basics
There is nothing impossible to him who will try.
Said by Alexander the Great

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Test Your Self
1) What will be the output of the following code?
if(a.equals(b))
System.out.println(“Same “);
else
System.out.println(“Not Same “);
Java Basics

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Test Your Self contd…
String c=a;
String d=b;
if(a==c)
System.out.println(“Same Reference “);
else
System.out.println(“Not Same Reference “);
if(b==d)
System.out.println(“Same b and d Reference“);
else
System.out.println(“Not Same b and d reference “);
Java Basics

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Java Coding Convention
Class and Interfaces – The First letter should be capital, and first
letter of the inner words should be Capital.
Example : Account
PrintWriter
Emp
Methods – The First Letter should be lowercase, and then normal
camelCase rules should be used.
Example : getBalance
setCustomerName
Variables – Same rule as Method Rule
Constants – All in Uppercase.
Example : MIN_HEIGHT
Java Basics

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What can you say in the main method?
•Write Sequential Statements
•Conditional Branching
•Looping
Java Basics

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 Writing Sequential Statements
Example:
class Test
{
{
int a,b,c; //declaring primitive variables
a=100;
b=200;
c=a+b;
System.out.println(“Sum is “+c);
} //main close
} //class close
Java Basics

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Exercise: To Do YourSelf
1) WAP to swap two numbers.
2) WAP to calculate simple interest
3) WAP to calculate area and perimeter of a rectangle
4) WAP to calculate net salary of employee, take basic
salary of employee and calculate Hra 30% of basic salary,
DA 20% of the basic salary, Ta 10% of the basic salary and
net salary is sum up of basic salary+ allowances-pf. Pf is
1400 fix.
Note : Follow Java Conventions during coding
Java Basics

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Java Decision Making Statements
1) Using if-else
2) Using switch
Java Basics

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 Decision Making Programs
Example 1
class Test
{
{
int a,b;
a=100;
b=200;
if(a>b) //required boolean true or false
System.out.println(“A is Greater “);
else
System.out.println(“B is Greater “);
}
}
Java Basics

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class Test
{
{
int a=2;
switch(a)
{
case 1:
System.out.println(“Sunday “);
break;
case 2:
System.out.println(“Monday “);
break;
case 3:
System.out.println(“Tuesday”);
break;
case 4:
System.out.println(“Wednesday “);
break;
case 5:
System.out.println(“Thursday “);
break;
case 6:
System.out.println(“Friday “);
break;
Java Basics
Example 2:
case 7:
System.out.println(“saturday “);
break;
default:
System.out.println(“Invalid Day “);
}
}
}
Note: Switch only allowed
int ,byte, char type

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TEST YOUR SELF
Your Purpose in life is to find your purpose and give your whole heart and soul to it.
Said by Buddha

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Test Your Self
Java Basics
class Test
{
{
int a=10;
if(a=20)
System.out.println(“TRUE”);
else
System.out.println(“False “);
}
}
a) Print TRUE b) Print False
c) Compilation Fail d) None of these

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class Test
{
{
String name=”Mike”;
int age=21;
if((name.equals(“Mike”)) && age>=21)
System.out.println(“Welcome “+name);
else
System.out.println(“Bye “+name);
}
}
Java Basics

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class Test
{
{
int color=2;
switch(color)
{
case 1:
System.out.println(“RED “);
default:
System.out.println(“GREEN”);
case 3:
System.out.println(“BLUE”);
}
}
}
Java Basics

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class Test
{
{
int color=2;
switch(color)
{
case 1:
System.out.println(“RED “);
break;
default:
System.out.println(“GREEN”);
break;
case 3:
System.out.println(“BLUE”);
break;
}}}
Java Basics

60
Exercise:
1) Find out entered number is Positive or Negative Number.
2) Find out the grade , according to given percentage of the user.
>=90 print A Grade
89 to 70 B Grade
69 to 50 C Grade
<50 D Grade
Java Basics

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3) A Insurance Company have a following polices (Insurance Premium
Calculation program)
User Input :
Person Name
Person gender
Person Age
Person city (Metro or Non-Metro)
Conditions:
if person age is 25 to 35 and gender is male and city is metro , Output is
Premium is 6%
if person age is 25 to 40 and gender is male and city is non-metro, Output
is Premium 4%
if person age is 25 to 42 and gender is female and city is Metro, Output is
Premium 3%
if person age is 25 to 45 and gender is female and city is non-metro , output
is Premium 2%
else Not Insured
Exercise: contd…
Java Basics

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When you want to repeat something for definite number of times,
it is called loop.
Java has three basic loops
a) for b) while c) do-while.
In JDK 1.5 java introduce one more loop called Enhance for
loop.
Java Basics
 LOOPING

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 JAVA LOOPS EXAMPLE
class Test
{
{
int i=1;
while(i<=10) //Need boolean test
{
System.out.println(“While Loop Value of i is “+i);
i++;
}
for(i=1;i<=10;i++)
{
System.out.println(“For Loop Value of i is “+i);
}
i=10;
do
{
System.out.println(“Do While Value of i is “+i);
}while(i<10);
}
}
Java Basics

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Enhance For Loop
Enhance for loop introduced in JDK 1.5 version
Example:
int a[]= {10,20, 30, 40, 50};
for(int x: a)
{
System.out.println(x);
}
Java Basics

65
TEST YOUR SELF
I hated every minute of training but I said, ‘Don’t quit. Suffer now and live the rest
of your life as a Champion.
Said by Muhammad Ali

66
Test Your Self
1) What will be the output of the following code
class Test
{
{
for(int i=1;i<=3;i++)
{
for(int j=1;j<=3;j++)
{
System.out.println(“Value of i is “+i +” Value of j is “+j);
} //j for loop close
} //i for loop close
} //main close
} //class close
Java Basics

67
class Test
{
{
String names [] = {“Ram”, “Shyam”, “Mohan”, “Sohan”};
for(int temp: names)
{
System.out.println(temp);
}
}
}
Java Basics

68
Java Basics
class Test
{
{
for(int i=1;i<=3;i++)
{
for(int j=1;j<=3;j++)
{
if(i==j)
continue;
else
System.out.println(“Value of i is “+i +” Value of j is “+j);
}
}
}
}

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Exercise:
1) WAP to count even number and odd number between 1 to 100.
2) WAP to count prime number between 1 to 100.
3) WAP to print sum of
1+2+3+.............................n
4) WAP to print sum of
12+22+32+..........................n2
Java Basics
5) Now i want to improve the functionality of the “Insurance Premium
Calculation program”.
Take the input of user details like name, gender, city and age, until user
enters “No”. If user enters ‘No’, then exit from the loop, else continue in the
loop. Take input again and check if eligibility for the insurance is there or not
, also count how many users are eligible and how many are not.

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Object Oriented Basics (OO Basics)
 OO and Procedural Programming WAR
 Object Oriented Features

71
A programmer primary task is to write software to solve a problem. Many
programming models have evolved to help programmers in being more effective.
Procedural Programming
One way of solving a problem is to break it down into smaller parts and solve each
of the smaller parts. Then aggregate (collate) all the parts to solve the overall
problem.
Think of each small part as task, to perform which you write a block of code is
called function. You can call one function from another.
This approach in software development is called process centric or Procedural.
For Example:

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Drawbacks of Procedural Programming
1. The code are so interdependent (due to one function call to another function) , so
one application code cannot be used in another application.
2. Interdependence between the modules so it is inflexible to change, So
maintaince is not easy.
3. This approach only good , if software engineer knows every aspects of project.
4. Not on Real world approach
5. Not good to solve large and complex problems

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An Object Oriented programming
Object oriented programming works on object instead of functions.
An object is a real world entity.
For Example:
Cat , Car , Ball are some of the examples of real world objects
An object represents two things
a) State – Dog has 4 legs , 1 tail , 2 ears . It shows the dog state
b) Behavior- are the functions or methods , that uses the state and shows
behavior of an object.
For example : dog jumps, so for this it is depend on legs
Now we take some more example
Amit is working as a Employee in Xyz Ltd.
So Amit represents an object of type Employee.
His states are empno is1010, Name is Amit Srivastava, Age is 27, and it’s
behavior are Attendance details, work details, salary calculation etc.
OO Basics

74
Object Oriented Programming and Procedural Programming WAR
OO Basics

76
Add one more shape in your current program
Contd.....
OO Basics

81
Conclusion of the Story
In Object Oriented Programming , Developer divide the problem into different objects
, instead of breaking the problem into functions (methods).
The Object is a real world entity.
For Example:
Amit is an object of class Employee
Royal Enfield is an object of Motor Bike
Object = State + Behavior
State represents the data items , for example : State of Amit are Empno, Name , Age
, Gender, Deptno , PhoneNo etc.
Behavior represents the functions (methods) . For example : work details,
attendance details, salary calculation etc.

82
Object Oriented Features
1) Encapsulation
Encapsulation - Binding “Data and Method” into a single unit and good encapsulation
is when your Data is private/protected and your methods are public.
Example of Encapsulation is Human Brain, Capsule.
OO Basics
class Emp
{
int empno; //DATA
String name;
float sal;
void input() //METHOD
{
empno=1001;
name=”MIKE”;
sal=9090.00f;
}
void show()
{
System.out.println(“Empno is “+empno);
System.out.println(“Name is “+name);
System.out.println(“Sal is “+sal);
}
}

83
2) Abstraction- Working on the essential things and to forget the things which are
not essential for us.
For Example : If i drive my car from my house to market, so i have to know how to
use brakes, accelerator, gear, steering, horn , clutch etc., i don't need to know
internal working of these things.
Example of Abstraction in Java is abstract classes, interfaces.
Contd.....
OO Basics
HyperLink

84
3) Inheritance - Used to show parent - child relationship like one class inherit the
features of the other class, so it provide you the code reusability.
For Example:
A CAR IS A Vehicle, it means CAR inherits the feature of Vehicle like brakes,
wheels, horn, clutch etc.
Contd.....
OO Basics

85
Inheritance Example:
class Account
{
int accountno;
float balance;
void deposit()
{
}
void withdraw()
{
}
}
class SavingAccount extends Account
{
float rateOfInterest;
void calculateRoi()
{
}
}
OO Basics

86
4) Polymorphism- One thing having several forms.
Example: All Animals are eating, but each type has different eating habits like Dog eats Meat,
Cow eats grass etc.
Example: In a calculator we can add two Integer, two real number, three numbers so a same
method name is used to add two numbers, three numbers, four numbers, two int numbers ,
two float numbers etc. This term is called “Method Overloading”.
Sample Code:
void add(int x,int y)
{
System.out.println(x+y);
}
void add(float x,float y)
{
}
void add(int a,int b,int c)
{
System.out.println(a+b+c);
}
Object Oriented Features Contd......
OO Basics

87
5) Class- Contains state (instance variables) and behaviour
(methods). A template that describes the kinds of state and
behaviour that objects of its type support.
5.1) State (Instance variables) – Each Object (instance of a class)
will have its own unique set of instance variables as defined in the
class.
5.2) Behaviour (Methods) – Methods are where the class logic is
stored, and it work on instance variables.
6) Object – Is an instance of a class. When JVM encounters the
new keyword, it will use the same class to make an object. That
Object will have its own states, and access to all of the behaviour
defined by it's class.
Contd......
OO Basics

88
Example: Creating class and Object
class Emp
{
int empno; //Instance variables
String name;
float sal;
void input(int eno,String ename,float esal) //Methods
{
empno=empno;
name=ename;
sal=esal;
}
void show()
{
System.out.println(“Name is “+name);
System.out.println(“Sal is “+sal);
}
{
Emp ram=new Emp();
//Creating a new object, a new operator is used to allocate a memory for the object.
ram.input(1001,”Ram “, 9090.0f);
ram.show();
Emp shyam =new Emp();
shyam.input(1002,”Shyam”,8888.0f); shyam.show();
}
}
OO Basics
Sample Example

89
Memory Representation of Emp Class Object
empno=1001
name
sal=9090.0f
MIKE
obj
OO Basics
Sample Example

90
General formula for calculating memory usage
In general, the heap memory used by a Java object in JVM consists of:
an object header, consisting of a few bytes of "housekeeping" information;
"housekeeping" information, such as recording an object's class, ID and status flags
such as whether the object is currently reachable, currently synchronization-locked
etc.
memory for primitive fields, according to their size
memory for reference fields (4 bytes each);
padding: potentially a few "wasted" unused bytes after the object data, to make
every object start at an address that is a convenient multiple of bytes and reduce the
number of bits required to represent a pointer to an object.
In Hotspot, every object occupies a number of bytes that is a multiple of 8. If the
number of bytes required by an object for its header and fields is not a multiple 8, then
you round up to the next multiple of 8.

91
This means, for example, that:
a bare Object (With no instance Variable) takes up 8 bytes;
an instance of a class with a single boolean field takes up 16 bytes: 8 bytes of
header, 1 byte for the boolean and 7 bytes of "padding" to make the size up to a
multiple of 8;
an instance with eight boolean fields will also take up 16 bytes: 8 for the header, 8
for the booleans; since this is already a multiple of 8, no padding is needed;
an object with a two long fields, three int fields and a boolean will take up:
8 bytes for the header;
16 bytes for the 2 longs (8 each);
12 bytes for the 3 ints (4 each);
1 byte for the boolean;
a further 3 bytes of padding, to round the total up from 37 to 40, a multiple of 8.

92
Object Size get in Java
package com.example.demo
public class MyAgent {
public static void premain(String args, Instrumentation inst) {
SomeClass obj = new SomeClass();
long size = inst.getObjectSize(obj);
System.out.println("Bytes used by object: " + size);
}
{
System.out.println(“Inside Main “);
}
}
Package the Agent into JAR
Add the following entry in the Manifest.mf file
Premain-Class: com.example.demo.MyAgent
Main-class :com.example.demo.MyAgent
Run
java -javaagent:agent.jar –jar agent.jar

93
Improving the Emp class example by using JavaBean
Java Bean
Simple Java classes that have private instance members and
public setter and getter methods. It is a reusable component.
OO Basics

94
Example: Creating JavaBean
class Emp
{
private int empno;
private String name;
public void setEmpno(int empno) //Java Bean Rules
{
this.empno=empno; //Shadowing
}
public int getEmpno()
{
return empno;
}
public void setName(String name)
{
this.name=name;
}
public String getName()
{
return name;
}
}
NOTE: this is also called good encapsulation
OO Basics
Sample Example

95
TEST YOUR SELF
Nobody has the power to take two steps together; you can take only one step at a time.
Said by Osho

96
1) Check this is proper Java Bean.
class Customer
{
private int custId;
public String name;
public void setCustId(int custId)
{
this.custId=custId;
}
public int getCustId()
{
return custId;
}
public void setName(String name)
{
this.name=name;
}
public String getName()
{
return name;
}
}
OO Basics

97
2) TRUE – FALSE
a) Encapsulation means private methods and public variables.
b) extends is used for inheritance.
c) Overloading is an example of Abstraction.
d) Instance Variables live in a Stack.
e) new operator is used to allocate a memory for an object
f) object always of reference type.
g) Class is an instance of an object.
h) Local Variables and Methods live in a Stack.
OO Basics

98
Exercise :
1) Create a Student class which has rollno , name, 3 subject
marks(English , Hindi , Maths) calculate total marks, percentage and
grade. And print the Result Sheet of the Student.
2) Create a Employee class which has empno,name,basicSalary,
calculate HRA, DA , TA and GS.
HRA is 30% of basic salary
DA is 20% of basic salary
TA is 10% of basic salary
GS=BasicSalary+ hra+da+ta
OO Basics

99
Using Constructor
 About Constructor
 Calling One Constructor by another constructor

100
 Constructor
✔Constructor has same name as a class name.
✔It is same like a method.
✔It returns nothing.
✔It Call automatically when object is created.
✔It is used to initialize the instance variables of a class.
✔You can't make a new object without invoking a constructor.
✔Every class have a default constructor by default.
Using Constructor

101
class Emp
{
int empno;
String name;
float sal;
void input()
{
empno=1002;
name=”Mike”;
sal=9090.0f;
}
public static void main(String
args[])
{
Emp obj=new Emp();
System.out.println(obj.empno+
obj.name+obj.sal);
}}
class Emp
{
int empno;
String name;
float sal;
Emp()
{
empno=1001;
name=”TIM”;
sal=9090.0f;
}
{
Emp obj=new Emp();
System.out.println(obj.empno+obj.name+obj.sal)
;
}
}
Using Constructor
Example 1 Without Constructor Example 2 Using Constructor
Sample Example

102
Example 3:
class A
{
A() //the default constructor for the A Class
{
}
}
Example 4:
class A
{
A(int a)
{
}
}
A obj=new A(); //Won't compile , no matching constructor.
Example 5:
class A
{
A()
{
System.out.println(“I am default Constructor”);
}
void A()
{
System.out.println(“ I am not a constructor , i am a method ! “);
}
}
Contd….
Using Constructor

103
Calling One Constructor by another Constructor in same class
Example:
class A
{
private A()
{
System.out.println(“ I am default constructor of the A Class “);
}
A(int s) //Overloading of the Constructor
{
this(); // Must be the first statement
System.out.println(“I am the A class Parameterized Constructor “);
}
}
class Test
{
public static void main(String agrs[])
{
A obj=new A(); //Error because default constructor is private
A obj1=new A(100);
}
}
Using Constructor

104
TEST YOUR SELF
Don’t find a fault, find a remedy; anyone can complain
Said by Henry Ford

105
Test your Self
class A
{
A(int b)
{
System.out.println(“A class Constructor “);
}
{
A obj=new A();
}
}
Using Constructor

106
class A
{
A()
{
System.out.println(“A class Default Constructor Call “);
}
A(int x)
{
this();
System.out.println(“A class Parameterized Constructor Call “);
}
{
A obj=new A(10);
}
}
Using Constructor

107
Exercise:
Create a class Emp with empno,name,sal as instance variables
and then create two constructor default and parametrized to set
the values of instance members and create a method print() to
print the values.
Using Constructor

108
IS-A
 About Inheritance
 Inheritance Advantages
 Reference Variable Rules
 HAS-A
 Class Access Ways
 Access Modifiers
 Final class

109
IS-A
INHERITANCE TREE
LION IS-A Animal
Hippo IS-A Animal
Tiger IS-A Animal
Inheritance

110
Account
(Account number, balance)
Current Account Saving Account
LOAN
AutoLoan Personal
Loan
IS-A
Inheritance Example

111
Contd.......
Example:
class A
{
Feature1 ;
Feature 2;
}
class B extends A
{
Feature 3; // + Feature 1 and Feature 2 comes from class A
Feature 4;
}
Inheritance has two advantages
1. To Promote code reuse ability, so code redundancy is reduce.
2. To Use Polymorphism
IS-A
Sample Example

112
1) To Promote code reuse ability, so code redundancy is reduce.
class Person
{
int age;
String name;
String address;
void input()
{ age=21;
name=”TIM”;
address=”NewYork”; }
void print()
{
System.out.println(“Person Name is “+name);
System.out.println(“Person Age is “+age);
System.out.println(“Person Address is “+address);
}
}
class Emp extends Person
{
int empno;
String desig;
float sal;
public void empInput()
{
empno=1001;
desig=”Programmer”;
sal=9090.00f;
}
Inheritance First Advantage

113
Contd....
public void empPrint()
{
System.out.println(“Designation is “+desig);
System.out.println(“Salary is “+sal);
}
}
class Test
{
{
Emp obj=new Emp();
obj.input();
obj.empInput();
obj.print();
obj.empPrint();
}
}
IS-A

114
2) To Use Polymorphism
Polymorphism one thing with several forms.
Example:
class Animal
{
}
class Dog extends Animal
{
}
class Cat extends Animal
{
}
Animal a=new Animal();
a=new Dog();
a=new Cat();
Inheritance Second Advantage
IS-A

115
 Reference variable rule:
✔A reference variable can be only one type and once declared,
that type can never be changed.
✔A reference type determines the methods that can be
invoked on the object the variable is referring.
✔It can refer to the same type or the sub type.
✔A reference variable can be of class type or interface type.
✔Up casting allowed only ( parent can take own and sub-type)
but down casting not allowed (child cannot take parent type).
NOTE: we cannot make a single program with out inheritance in java,
because every class inherit java.lang.Object class.
NOTE: Java is a package centric language; the developer assumed that for
good organization and name scoping , you would put all the your classes into
packages.
IS-A

116
Exercise:
Person class
Student class
Emp class
IS-A
Account
Current Account Saving
Account

117
 HAS- A
Has a relationship is based on usage , rather than inheritance.
Has-A used by making an object of the other class in your class.
For Examples:
Horse HAS-A Halter,
Customer Has-A Loan
Sample Code:
class Loan
{
}
class Customer
{
Loan carLoan =new Loan();
}
IS-A

118
IS-A HAS-A
Used to create a parent child relationship. IS-
A is based on class inheritance or interface.
Has-A relationship is based on usage , rather
than inheritance
For Example: BMW is a Car, Horse is an
Animal, AutoLoan IS-A Loan
For Example: Horse HAS-A Halter,
Customer HAS-A Loan
IS-A can be use by extends or implements
keyword.
Has-A used by making an object of the other
class in your class.
Example:
class Loan
{
}
class AutoLoan extends Loan
{
}
Example:
class Customer
{
AutoLoan car=new AutoLoan();
}
class AutoLoan
{
}
Advantages of IS-A
1) To Promote code re useability, so code
redundancy is reduced.
2) To Use Polymorphism
Advantages of HAS-A
1) Can work on other class instance variables
& methods without inheriting that class.
 CLASS ACCESS WAYS
IS-A

119
Access Modifier
There are 4 access modifier. (private, public, protected, default)
Note: With class only 2 access modifier can apply. ( public and default).
✔public access modifier- When a method or variable member is
declared public, it means access with in a package or outside a
package.
✔private access modifier- Members marked private can't be accessed
by code in any class other than the class in which the private member
was declared.
✔protected access modifier - Access with in same package and can
access outside the package by using inheritance.
✔default access modifier- If we didn't place an access modifier in front
of the variable or method, the access control is default, which means
package level.
Note: Can Access Modifiers be applied to local variables ? NO!
IS-A

120
Example: Show Use of public access modifier
package book; package cert;
import cert.*; public class B
class A {
{
public static void main(String args[]) public void show()
{ {
B obj=new B(); System.out.println(“B Class Show “);
obj.show(); }
} }
}
IS-A

121
IS-A
Final class
final class A //final class cannot be inherit
{
}
class B extends A // You cannot inherit a final class
{
}
NOTE: String is a final class
Sample Example

122
TEST YOUR SELF
Nothing is particularly hard if you divide it into the small jobs.
Said by Henry Ford

123
Test Your Self
IS-A
class A
{
}
class B extends A
{
}
class C extends A, B
{
}

124
• What is the output:
class A
{
A()
{
System.out.println(“A Class Default Constructor Call “);
}
}
class B
{
B()
{
System.out.println(“B class Default Constructor Call “);
}
}
class Test
{ public static void main(String args[])
{
B obj=new B(); }
}
IS-A

125
class A
{
A(int a)
{
System.out.println(“A class Parameterized Constructor Call “);
}
}
class B extends A
{
B()
{
System.out.println(“B Class Default Constructor Call “);
}
}
class Test
{
{ B obj=new B(); }
}
IS-A
3) What is the output:

126
IS-A
class A
{
void showA()
{
System.out.println(“A show “);
}
}
final class B extends A
{
void showB()
{
System.out.println(“B Show “);
}
}
class Test
{
{
B obj=new B(); obj.showA(); obj.showB(); }
}

127
IS-A
class A
{
private int a=10;
public int b=20;
int c=30;
protected int d=40;
}
class B extends A
{
void add()
{
System.out.println(a+b+c+d);
}
{
B obj=new B();
obj.add();
}
}

128
Polymorphism
 Overloading
 Overriding
 Using final in Overriding
 Overloading vs Overriding
 super vs this

129
Polymorphism- One thing with several forms.
For Example: All Animals are eating, but each type has different eating habits like Dog eats
Meat, Cow eats grass etc.
For Example: In calculator we can add two Integer, two real number, three numbers so a
same method name is used to add two numbers, three numbers, four numbers, two int
numbers , two float numbers etc.
Sample Code:
void add(int x,int y)
{
}
void add(float x,float y)
{
}
void add(int a,int b,int c)
{
System.out.println(a+b+c);
}
Polymorphism

130
 Overloading
Overloaded methods can be reused as the same method name in a class,
but with different arguments and optionally , a different return type.
Example : A search method on Banking System, to search its customer by
name, or by address or by dob, or by phone number, or by customer id.
Sample Code:
boolean search(int custid)
boolean search(String name,String address)
boolean search(String name,Date dob)
boolean search(String name,String phoneno)
Polymorphism
Sample Example

131
Overloading Example:
class Calculator
{
public void add(int x,int y)
{
}
public void add(int x,int y, int z)
{
System.out.println(x+y+z);
}
public void add(float x,float y)
{
}
public int add(long x,long y)
{
return (x+y);
}
{
Calculator obj=new Calculator();
obj.add(10,20);
obj.add(10,20,30);
obj,add(10.1f,20.2f);
obj.add(10l,20l);
}
}
Polymorphism

132
 Overriding
Polymorphism

133
Overridden Methods
Any time you have a class that inherits a method from a superclass, you have the
opportunity to override the method.
Example:
class Animal
{
public void eat()
{
System.out.println(“Generic Animal eating Generically “);
}
}
class Dog extends Animal
{
public void eat()
{
System.out.println(“EAT MEAT”);
}
}
class Cow extends Animal
{
public void eat()
{
System.out.println(“EAT GRASS “);
}
}
Here eat() method overridden
Polymorphism
Sample Example

134
class Account
{
void withdraw() { }
void deposit() { }
void rateOfInterest() { }
}
class CurrentAccount extends Account
{
public void rateOfInterest()
{
}
}
{
public void rateOfInterest()
{
}
}
Polymorphism
Overriding Example
Sample Example

135
Polymorphism
Using final in Overriding
class A
{
final void show()
{
}
}
class B extends A
{
void show() //Compilation Fails because show is defined final , and we cannot
//override a final method.
{
}
}

136
Polymorphism
Overloading Overriding
Any time you have a class that inherits a
method from a superclass, you have the
opportunity to override the method.
Overloaded methods let you reuse the same
method name in a class, but with different
arguments( and optionally , a different return
type.
The argument list must be same. Overloaded methods must change the
argument list.
The return type must be same in jdk1.4, but
in jdk1.5 it should be co-variant returns
Overloaded methods can change the return
type.
The access level can't be less restrictive in
Overridden method.
Overloaded methods can change the
access modifier.
Can throw any unchecked exception by
Overriding.
The Overridden method can throw any sub
type or same type exception of overriding
method.
Overloaded methods can declare new or
broader checked exceptions.
Without inheritance no Overriding. A method can be overloaded in the same
class or in a subclass.
You cannot override a method marked final.
You cannot override a method marked
static.
Can overload final and static methods.

137
Widening in Overloading
Widening always use same or bigger data type, not go for the smaller.
Example: What is the output
class A {
void show(int x) { System.out.println(“Show Int “); }
void show(byte x) { System.out.println(“Show byte “); }
void show(long x) { System.out.println(“Show long “); }
public static void main(String args[]) {
A obj = new A();
Obj.show(10);
}
}

138
The compiler will choose the older style before it chooses the newer style,
keeping existing code more robust. So far we've seen that
1) Widening beats boxing
2) Widening beats var-args
Example: AutoBoxing Happens Automatically
class AddBoxing {
static void go(Integer x) { System.out.println("Integer"); }
public static void main(String [] args) {
int i = 5;
go(i);
}
}
Overloading Rules

139
Example: Here widening Happens
class AddBoxing {
static void go(long x) { System.out.println("long"); }
int i = 5;
go(i);
}
}
Example : Here Widening Beats Boxing
class AddBoxing {
static void go(Integer x) { System.out.println("Integer"); }
static void go(long x) { System.out.println("long"); }
int i = 5;
go(i); // which go() will be invoked?
}
}

140
Example : Here Wrapper classes Beats Var-args
class BoxOrVararg {
static void go(Byte x, Byte y){ System.out.println("Byte, Byte"); }
static void go(byte... x) { System.out.println("byte... "); }
byte b = 5;
go(b,b); // which go() will be invoked?
}
}
Example: Here Mixing Wideing and Autoboxing, The Java Compiler not able
to do it both, so it will give error
class WidenAndBox {
static void go(Long x) { System.out.println("Long"); }
byte b = 5;
go(b); // must widen then box - illegal
}
}

141
1) Static binding in Java occurs during Compile time while Dynamic binding
occurs during Runtime.
2) Static binding uses Type(Class in Java) information for binding while
Dynamic binding uses Object to resolve binding
3) Overloaded methods are bonded using static binding while overridden
methods are bonded during run time (Dynamic Binding).
4) Instance Variable bound with static binding.
Static v/s Dynamic Binding

142
public class StaticBindingTest {
Collection c = new HashSet();
StaticBindingTest et = new StaticBindingTest();
et.sort(c);
}
//overloaded method takes Collection argument
public Collection sort(Collection c){
System.out.println("Inside Collection sort method");
return c;
}
//another overloaded method which takes HashSet argument which is sub class
public Collection sort(HashSet hs){
System.out.println("Inside HashSet sort method");
return hs;
}
}
Output:
Inside Collection sort method
Static Binding Demo

143
Dynamic Binding Demo
public class DynamicBindingTest {
Vehicle vehicle = new Car(); //here Type is vehicle but object will be Car
vehicle.start(); //Car's start called because start() is overridden method
}
}
class Vehicle {
public void start() {
System.out.println("Inside start method of Vehicle");
}
}
class Car extends Vehicle {
public void start() {
System.out.println("Inside start method of Car");
}
}
Output:
Inside start method of Car

144
TEST YOUR SELF
A person who never made a mistake never tried anything new.
Said by Albert Einstein

145
TEST YOUR SELF
class A
{
void show()
{
System.out.println(“ A class Show Call “);
}
}
class B extends A
{
String show()
{
System.out.println(“B Class show call “);
}
}
B obj=new B(); obj.show();
Polymorphism

146
TEST YOUR SELF contd…
2) What is this , Overloading or Overriding?
class A
{
void show()
{
}
}
class B extends A
{
void show(int i)
{
}
}
Polymorphism

147
TEST YOUR SELF contd….
class A
{
public void show()
{
}
}
class B extends A
{
void show()
{
}
}
Polymorphism

148
TEST YOUR SELF contd….
class A
{
private final void show()
{
}
}
class B extends A
{
void show()
{
}
}
Polymorphism

149
super this
Super keyword always refers to the parent
elements like parent method , parent
constructor, parent instance variables.
This keyword always refers to the current
class elements like methods, constructors,
instance variables.
Calling parent class method by using super.
Example:
super.parentClassMethodName();
Calling current class method.
Example :
this.currentClassMethodName();
Calling parent class constructor.
Example:
super();
super(100);
Calling current class constructor.
Example:
this();
this(100);
Using parent class variable in child class.
super.a=100;
Using current class variable.
Example:
this.a=100;
 super vs this
Polymorphism

150
Use of super and this keyword
Example 1
class A
{
int temp=10;
void show()
{
System.out.println(“ A Sho w”);
}
}
class B extends A
{
int temp=20;
void show()
{
super.show(); //Use of super to call parent class method
System.out.println(“B Show “);
this.temp=super.temp+this.temp;
}
}
class Test
{
{
B obj=new B();
obj.show();
}
Polymorphism

151
Example 2 Another use of super and this use
class A
{
A()
{ System.out.println(“A Class Default Constructor Call “); }
A(int a)
{
System.out.println(“A class Parameterized Constructor call “);
}
}
class B extends A
{
B()
{
System.out.println(“B Class Default Constructor Call “);
}
B(int t)
{
super(10); //Use of super to call parent class parameterized constructor and it must be the
first line.
System.out.println(“B Class Parameterized Constructor call “);
}
}
Polymorphism

152
TEST YOUR SELF
Success is the sum of small efforts, repeated day in and day out.
Robert Collier

153
class A
{
A()
{
this(10);
System.out.println(“A Class Default Constructor “);
}
A(int a)
{
System.out.println(“A class Parameterized Constructor “);
}
}
class B extends A
{
B()
{
System.out.println(“B Class Default Constructor “);
}
{
B obj=new B(); }
}
Polymorphism

154
Abstract Class
 Abstract class Intro
 Abstract Methods

155
Abstract class
An abstract class never be instantiated. It is used by extending it.
Abstract class has generic methods (Abstract methods) common to all sub –
classes .
Abstract methods are body less methods (Methods Prototypes) and
child classes override the abstract methods.
Example:
abstract class Account
{
public void deposit()
{
}
public void withdraw()
{
}
public void checkBalance()
{
}
public abstract float rateOfInterest();
public abstract String[] services();
}
Abstract class

156
{
public float rateOfInterest()
{
}
public String[] services()
{
}
}
class CurrentAccount extends Account
{
public float rateOfInterest()
{
}
//Now this class become abstract , if you not override all the abstract methods
//of abstract class, your class become abstract too.
}
Abstract class

157
TEST YOUR SELF
The difference between a successful person and others is not a lack of
strength, not a lack of knowledge, but rather a lack in will.
Vince Lombardi

158
class Account
{
abstract void deposit();
}
{
void deposit()
{
System.out.println(“Deposit Call “);
}
{
SavingAccount obj=new SavingAccount();
obj.deposit();
}
}
Abstract class

159
{
void deposit()
{
System.out.println(“Abstract class Deposit Call “);
}
}
{
void deposit()
{
}
{
obj.deposit();
}
}
Abstract class

160
{
abstract void deposit();
}
{
void deposit(int a)
{
}
{
obj.deposit(11);
}
}
Abstract class

161
Interface
 Interface Introduction
 Interface On Job
 Interface Coding techniques

163
Interfaces
Interface contains method prototypes (body less methods) and constants.
When you create an interface, you're defining a contract for what a class can do,
without saying anything about how the class will do it.
Interface

164
Interface Example:
interface Animal
{
int LEGS=4; //public static final LEGS=4;
void eat(); //public abstract void eat();
void sound(); //public abstract void sound();
}
class Dog implements Animal
{
public void eat()
{
System.out.println(“EAT MEAT “);
}
public void sound()
{
System.out.println(“BARK “);
}
}
class Cow implements Animal
{
public void eat()
{
System.out.println(“EAT GRASS “);
}
public void sound()
{
System.out.println(“MOO “);
}
}
Interface
Sample Example

165
public interface CustOperation
{
public int insert(Customer obj) ;
public int update(int custid,Customer obj);
public int delete(Customer obj);
public void select(Customer obj) ;
}
NOTE: Create a Customer Bean (Customerid, Customer Name,
Gender, Address , Phone).
 Interface on JOB
Interface

166
 Interface Coding techniques
Example 1:
interface A
{
int x=10; //internally public static final int x=10;
void show(); //convert internally to public abstract void show()
}
interface B extends A
{
void disp(); //public abstract void disp();
}
Example 2:
interface A
{
void show();
}
interface B
{
void disp();
}
interface C extends A,B //Multiple inheritance can be possible using interface.
{
}
Interface

167
Contd.....
Example 3:
interface Animal
{
void sleep();
void eat();
}
interface Pet
{
void faithful();
}
class Dog implements Animal,Pet
{
public void sleep()
{
}
public void eat()
{
}
public void faithful()
{
}
}
NOTE:
1) You implement an interface by properly and concretely overriding all of the
methods defined by the interface.
2) A single class can implement many interfaces.
Interface

168
TEST YOUR SELF
He who has never learned to obey
cannot be a good commander.
Aristotle

169
Test Your Self
interface X
{
void show();
}
class Y extends X
{
public void show()
{
System.out.println(“Inside Y Show “)
}
}
Interface

170
2) what will be the output of the following code?
interface X
{
void show();
}
class Y implements X
{
void show()
{
System.out.println(“Inside Y Show “);
}
}
Test Your Self contd….
Interface

171
3) what will be the output of the following code?
interface X
{
void show();
}
interface Y implements X
{
void disp();
}
class Z extends Y
{
public void show()
{
System.out.println(“ Inside show “);
}
}
Test Your Self contd….
Interface

172
Exercise:
1) Create an interface CustOperation which have insert, delete, print
methods and a customer class implements CustOperation interface and
overrides it's all methods.
2) Create three interfaces Account interface, Emp interface, Bank interface.
Account interface has emp loan method, leave detail method. Emp interface
has salary calculate method and bank has deposit and withdraw method.
And finally we have a payroll interface which inherit all these interfaces.
And Nucleus class implements all these interfaces.

173
Pass By Value
And
Pass By Reference

174
Pass by Value Pass By Reference
It means passing a primitive variable into
method.
It means passing an object reference to the
method.
Pass by variable means Pass by copy of the
variable.
When you pass an object variable into
method, you must keep in mind that you're
passing the object reference, and not the
actual object it self.
So for the primitive variable, you are always
passing a copy of bits in the variable.
Passing the copy of reference variable to the
method. In other words , both the caller and
the called method will now have identical
copies of the reference, and thus both will
refer to the exact (not a copy ) object on the
heap.
Note: It makes no difference if you're passing primitive or reference variables, you are always passing a
copy of bits in the variable.

175
class X
{
void modify(int x,int y)
{
x++;
y++;
System.out.println(“Value of x is “+x+” and y is “+y);
}
}
class Test
{
{
X obj=new X();
int a=100,int b=200;
obj.modify(a,b);
System.out.println(“After Modification Values are “+a+” “+b);
}
}
a=100 b=200
x=101 y=201
Pass by value Example

176
Pass By Reference
class X
{
int a,b;
X()
{
a=100;
b=200;
System.out.println(“Inside X Default Constructor “);
}
void modify(X obj)
{
obj.a++;
obj.b++;
System.out.println(“Value of a is “+obj.a+” and b is “+obj.b);
}
}
class Test
{
{
X temp=new X();
temp.modify(temp);
System.out.println(“Value of a and b inside main “+temp.a+temp.b);
}
}
temp=1080
a=100
b=200
1080
HEAP
obj=1080

177
Static member
 Static Variable
 Static Method

178
Static variable
Value is the same for all instances of the class.
Static variables are shared.
All instances of the same class share a single copy of the static variables.
Note : Instance variables 1 per instance.
Static variables 1 per class
Static member

179
class Emp
{
static int empCount;
private int empno;
Emp()
{
empCount++;
}
public void setEmpno(int empno)
{
this.empno=empno;
}
public int getEmpno()
{
return empno;
}
{
Emp ram=new Emp();
ram.setEmpno(1001);
Emp shyam=new Emp();
shyam.setEmpno(1002);
}
}
Static example
Static member
Sample Example

180
Static Method
Static methods are same like instance methods, but it is static so it is shareable
to all objects.
Static methods can use only static members or local variables , it cannot use
non – static members.
Static method access directly with-out creating an object of a class.
Example:
class A
{
static void show()
{
System.out.println(“Inside Show “);
}
}
class Test
{
{
A.show(); } }
Static member
Sample Example

181
TEST YOUR SELF
Static member
Experience is the child of thought, and thought is the child
of action. We cannot learn men from books.
Benjamin Disraeli

182
class Test
{
int a=100,b=200;
static void add()
{
int c=a+b;
System.out.println(“Sum is “+c);
}
{
add();
}
}
Static member

183
2) What will be the output of the following code ?
class Test
{
static int a;
int b;
Test()
{
a++;
b++;
System.out.println(“A Value is “+a);
System.out.println(“B Value is “+b);
}
{
Test obj1=new Test();
}
}
Static member

184
JDK 1.5
1. Enhance For Loop
2. Var – Args
3. AutoBoxing
4. Static import
5. Annotations
6. Generics
7. Enum

186
A Java virtual machine's main job is to load class files and execute the
bytecodes they contain .

191
Treatment of boolean data type in the Java
When a compiler translates Java source code into bytecodes, it uses ints
or bytes to represent booleans. In the Java virtual machine, false is represented
by integer zero and true by any non-zero integer.
The Java virtual machine works with one other primitive type that is unavailable
to the Java programmer: thereturnAddress type
returnAddress types are pointers to the opcodes of JVM instructions.

193
An instance of class java.lang.Class is created by the Java
virtual machine for every type it loads. The virtual machine
must in some way associate a reference to
the Class instance for a type with the type's data in the
method area.

194
Object Representation in Memory
a) Splitting an object across a handle pool and object pool.
Advantage is Heap size is Compact.
Two Reference need to maintain in Heap one for instance data and
other for Method area.
b) Keeping object data all in one place
Only one reference need to maintain in heap is only for the method
area

195
a) Splitting an object across a handle pool and object pool.

196
b) Keeping object data all in one place

198
Array Representation in Memory
In Java, arrays are full-fledged objects. Like objects, arrays are always stored on
the heap. Also like objects, implementation designers can decide how they want
to represent arrays on the heap.
Arrays have a Class instance associated with their class, just like any other
object. All arrays of the same dimension and type have the same class. The
length of an array (or the lengths of each dimension of a multidimensional array)
does not play any role in establishing the array's class. For example, an array of
threeints has the same class as an array of three hundred ints. The length of an
array is considered part of its instance data.
The name of an array's class has one open square bracket for each dimension
plus a letter or string representing the array's type. For example, the class name
for an array of ints is "[I"

201
The Java virtual machine makes types available to the running program through
a process of loading, linking, andinitialization.
1. Loading is the process of bringing a binary form for a type into the Java virtual
machine.
2. Linking is the process of incorporating the binary type data into the runtime
state of the virtual machine.
3. Linking is divided into three sub-steps: verification, preparation,
and resolution.
3.1 Verification ensures the type is properly formed and fit for use by the Java
virtual machine.
3.2 Preparation involves allocating memory needed by the type, such as memory
for any class variables.
3.3 Resolution is the process of transforming symbolic references in the constant
pool into direct references.
Implementations may delay the resolution step until each symbolic reference is
actually used by the running program.
NOTE : After verification, preparation, and (optionally) resolution are completed,
the type is ready for initialization.
Object Creation Steps

202
Garbage Collection
Any garbage collection (GC) algorithm must do two basic things.
First, it must detect garbage objects.
Second, it must reclaim the heap space used by the garbage objects and make
the space available again to the program.
It determining reachability from the roots.
An object is reachable if there is some path of references from the roots by which
the executing program can access the object.
The roots are always accessible to the program. Any objects that are reachable
from the roots are considered "live."
Objects that are not reachable are considered garbage,

203
to determine garbage collection, start your app as –
java –verbose:gc HelloWorld
The output of above change should be something like –
GC 325407K->83000K(776768K), 0.2300771 secs
GC – Indicates that it was a minor collection (young generation).
If it had said Full GC then that indicates that it was a major collection (tenured
generation).
325407K – The combined size of live objects before garbage collection.
83000K – The combined size of live objects after garbage collection.
(776768K) – the total available space, not counting the space in the permanent
generation,
which is the total heap minus one of the survivor spaces.
0.2300771 secs – time it took for garbage collection to occur.
Full GC Example:
[Full GC [Tenured: 3485K->4095K(4096K), 0.1745373 secs] 61244K-
>7418K(63104K), [Perm : 10756K->10756K(12288K)], 0.1762129 secs] [Times:
user=0.19 sys=0.00, real=0.19 secs]

204
Inside Heap
As we know objects are created inside heap memory and Garbage collection
is a process which removes dead objects from Java Heap space and returns
memory back to Heap in Java.
For the sake of Garbage collection Heap is divided into three main regions
named as New Generation, Old or Tenured Generation and Perm space.
New Generation of Java Heap is part of Java Heap memory where newly
created object are stored,
During the course of application many objects created and died but those
remain live they got moved to Old or Tenured Generation by Java Garbage
collector thread.
Perm space of Java Heap is where JVM stores Meta data about classes and
methods, String pool and Class level details.

205
1) objects are created on heap in Java irrespective of there scope e.g. local or member
variable. while its worth noting that class variables or static members are created in method
area of Java memory space and both heap and method area is shared between different
thread.
2) Garbage collection is a mechanism provided by Java Virtual Machine to reclaim heap
space from objects which are eligible for Garbage collection.
3) Garbage collection relieves java programmer from memory management which is
essential part of C++ programming and gives more time to focus on business logic.
4) Garbage Collection in Java is carried by a daemon thread called Garbage Collector.
5) Before removing an object from memory Garbage collection thread invokes finalize ()
method of that object and gives an opportunity to perform any sort of cleanup required.
6) You as Java programmer can not force Garbage collection in Java; it will only trigger if
JVM thinks it needs a garbage collection based on Java heap size.
7) There are methods like System.gc () and Runtime.gc () which is used to send request
of Garbage collection to JVM but it’s not guaranteed that garbage collection will happen.
8) If there is no memory space for creating new object in Heap Java Virtual
Machine throws OutOfMemoryError or java.lang.OutOfMemoryError heap space
9) J2SE 5(Java 2 Standard Edition) adds a new feature called Ergonomics goal of
ergonomics is to provide good performance from the JVM with minimum of command
line tuning.

207
Java Memory Types
Java objects are created in Heap and Heap is divided into two parts or
generations for sake of garbage collection in Java, these are called as Young
generation or New Generation, Tenured or Old Generation.
Young Generation or New Generation is further divided into three parts
known as Eden space, Survivor 1 and Survivor 2 space.
When an object first created in heap its gets created in new generation inside
Eden space and after subsequent Minor Garbage collection if
object survives its gets moved to survivor 1 and then Survivor 2.
before Major Garbage collection moved that object toOld or tenured
generation.
Old Generation – It has 2 parts Tenured Generation and Permant Generation
(PermGen) . After Surviour2 objects are move to Tenured Generation.
Permanent generation or Perm Area is somewhat special and it is used to store
Meta data related to classes and method in JVM. And only Perm Gen is part of
Non-Heap Memory.

208
There are some GC algorithms which can be used by a Java VM. The following
command line options allow to use a specific GC algorithm:
-XX:+UseSerialGC -> single threaded, young generation, and old generation garbage
collector (should be used only for small Java heap sizes such as -Xmx256m or
smaller)
-XX:+UseParallelGC -> only the young generation space utilizes a multithreaded
(parallel) garbage collector.The old generation space uses a single-threaded
garbage collector.
-XX:+UseParallelOldGC -> both young and old generations use multithread garbage
collector.
-XX:+UseParNewGC -> enables a multithreaded, young generation garbage collector
-XX:+UseConcMarkSweepGC -> enables the VM’s mostly concurrent garbage
collector. It also auto-enables -XX:+UseParNewGC (use if If you are not able to meet
your application’s worst case latency requirements due to full garbage collection
duration being too long)
-XX:+UseG1GC -> garbage first collector (default in java 7, can be also used in latest
releases of java 6)

209
The G1 Garbage Collector
The Garbage-First (G1) collector is a server-style garbage collector, targeted for
multi-processor machines with large memories. It meets garbage collection (GC)
pause time goals with a high probability, while achieving high throughput. The G1
garbage collector is fully supported in Oracle JDK 7 update 4 and later releases.
The G1 collector is designed for applications that:
Can operate concurrently with applications threads like the CMS collector.
Compact free space without lengthy GC induced pause times.
Need more predictable GC pause durations.
Do not want to sacrifice a lot of throughput performance.
Do not require a much larger Java heap.
G1 is planned as the long term replacement for the Concurrent Mark-Sweep
Collector (CMS). Comparing G1 with CMS, there are differences that make G1 a
better solution. One difference is that G1 is a compacting collector. G1 compacts
sufficiently to completely avoid the use of fine-grained free lists for allocation,
and instead relies on regions. This considerably simplifies parts of the collector,
and mostly eliminates potential fragmentation issues. Also, G1 offers more
predictable garbage collection pauses than the CMS collector, and allows users
to specify desired pause targets.

210
Monitoring the Garbage Collection
GC is done by JVM, and since the GC monitoring tools disclose the GC
information provided by JVM, you will get the same results no matter how you
monitor GC.
First, the GC monitoring methods can be separated into CUI and GUI depending
on the access interface. The typical CUI GC monitoring method involves using a
separate CUI application called "jstat", or selecting a JVM option called
"verbosegc" when running JVM.
GUI GC monitoring is done by using a separate GUI application, and three most
commonly used applications would be "jconsole", "jvisualvm" .

211
CUI GC
1. java –verbose:gc HelloWorld
2. Java -XX:+PrintGCDetails HelloWorld
3. Java XX:+PrintGCTimeStamps HelloWorld
2. jstat is a monitoring tool in JVM
jstat –gc <pid>
Where pid is the process id and you can get the java process id.
By using jps command
jstat does not provide only the GC operation information display. It also
provides class loader operation information or Just-in-Time compiler operation
information.

212
GUI GC
1. Java Visual VM is a GUI profiling/monitoring tool.
visualvm_134visualvm_134binvisualvm.exe – to run simple run the exe
file.

213
GUI GC
2. Jconsole
This command comes with jdk
Syntax:
Jconsole <processid>
You can get the process id by using the jps

214
Summary on Garbage collection in Java
1) Java Heap is divided into three generation for sake of garbage collection. These
are young generation, tenured or old generation and Perm area.
2) New objects are created into young generation and subsequently moved
to old generation.
3) String pool is created in Perm area of Heap, garbage collection can occur in
perm space but depends upon JVM to JVM.
4) Minor garbage collection is used to move object from Eden space to
Survivor 1 and Survivor 2 space and Major collection is used to move object
from young to tenured generation.
5) Whenever Major garbage collection occurs application threads stops during
that period which will reduce application’s performance and throughput.
6) There are few performance improvement has been applied in garbage
collection in java 6 and we usually use JRE 1.6.20 for running our application.
7) JVM command line options –Xmx and -Xms is used to setup starting and
max size for Java Heap. Ideal ratio of this parameter is either 1:1 or 1:1.5 based
upon my experience for example you can have either both –Xmx and –Xms as
1GB or –Xms 1.2 GB and 1.8 GB.
8) There is no manual way of doing garbage collection in Java.

215
How to increase size of Java Heap
Default size of Heap space in Java is 128MB on most of 32 bit
Sun's JVM but its highly varies from JVM to JVM.
Maximum 64 MB Perm Space by Default and can extend to 128 MB in 32
Bit Window O/S.
VM options -Xms and -Xmx
java -Xms64m -Xmx256m HelloWorld
Java -XX:PermSize 128m HelloWorld
Java -Xss 1024m HelloWorld

217
Java Commands and Usage
Javac command
javac –verbose A.java
Javac –source 1.4 A.java
Javac –cp
Javac –classpath
Javap –verbose
Java –verbose
Java DeCompiler Usage

218
Using Runtime Class for GC and Heap Analysis
Using System Class for GC and System Properties

219
NOTE:
You cannot call this() from methods, only from constructors. If you do call this()in
a constructor, you must call it first, before any other code in the constructor, and
you can only call it once.
Instance initialization methods
When you compile a class, the Java compiler creates an instance initialization
method for each constructor you declare in the source code of the class. Although
the constructor is not a method, the instance initialization method is. It has a
name, <init>, a return type, void, and a set of parameters that match the
parameters of the constructor from which it was generated. For example, given
the following two constructors in the source file for class CoffeeCup:

220
// In source packet in file init/ex8/CoffeeCup.java class CoffeeCup { public
CoffeeCup() { //... } public CoffeeCup(int amount) { //... } // ... } the compiler would
generate the following two instance initialization methods in the class file for
class CoffeeCup, one for each constructor in the source file:
// In binary form in file init/ex8/CoffeeCup.class: public void (CoffeeCup this) {...}
public void (CoffeeCup this, int amount) {...} Note that <init> is not a valid Java
method name, so you could not define a method in your source file that
accidentally conflicted with an instance initialization method. (<init> is not a
method in the Java language sense of the term, because it has an illegal name.
In the compiled, binary Java class file, however, it is a legal method.)
Also, the this reference passed as the first parameter to <init> is inserted by the
Java compiler into the parameter list of every instance method. For example, the
method void add(int amount) in the source file for class CoffeeCup would become
the void add(CoffeeCup this, int amount) method in the class file. The
hidden this reference is the way in which instance methods, including instance
initialization methods, are able to access instance data.

221
OOAD
Object Oriented Analysis and Design

222
We build software to solve problems.
People have problems.
Therefore, we build software for people.
Good software not only solves
immediate problems, but it can be
maintained and modified to address the
inevitable changes that the customer
will want.

223
Three steps to great software
1. Make sure the software
does what the customer
wants
2. Apply good object-oriented
principles
3. Strive for a maintainable,
reusable design
223

224
We create software for a reason.
We create software fro people.
We need to know what the people want in
the software we build.
These are called REQUIREMENTS.

225
1
2
3
4
5
Who provides requirements?
225
We call these people Stakeholders
Customer
End user
Development team members
Management
Technology providers

226
What is a requirement?
226
‣ A requirement is a feature that your system must
have in order to satisfy the customer.
‣ A requirement is something your system must do.
Did we meet the requirements?

227
Define the problem
• Talk to the customer
• Talk to other stakeholders
• Ask questions
• Brainstorm
• Look at the problem from many
points of view
227

228
Improper requirement gathering result

229
Welcome to use cases
•A use case is
– A complete sequence of
steps that provides value to
someone
– Something your system
must do
– Initiated by an Actor
(someone or something not
part of your system)
229

230
230
‣ Provide value
‣ Are complete
‣ Are initiated by an actor
‣ Describe a single goal of the system
‣ Be described by UML diagrams with text
‣ Be formally structured
‣ Be described using a language with formal semantics
‣ Be described by using software tools
Use cases definitely…
Use cases may…
The essence of use cases

231
Parts of a use case
231
Name:
Usually verb-noun (e.g. enroll in course)
Description:
A paragraph or two describing the purpose and value
(results)
Actors:
Name the actor(s) involved
Basic Flow:
The most common or expected path through the use case
Alternate Flows:
Those paths or exceptions that can occur
Preconditions:
Things that must be true before the use case can begin
Postconditions:
Things that must be true when the use case ends
successfully

232
232
And you’re responsible for
changing your programs

233
What might change?
233
Hardware (new and modified)
The use case
The code (implementation and tests)
Technology Upgrade
1
2
3
4

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