Introduction to Java

Java/J2EE Programming Training
Introduction to Java

Classification: Restricted
Agenda
• Understand the advantages of Java
• Understand where Java is used
• Understand how memory management is handled in Java
• Create a Java project in Eclipse and execute it
• Implement if..else construct in Java
• Develop codes using various data types in Java
• Implement various loops

Meet John
• Mike is a student of Computer Science in
California University.

John learns about Programming Languages

John is Confused

John gets a Bookish Answer

John is Still Confused

John heads home with a doub’t

John meets his Brother

John expresses his concerns

John gets an Answer!

John wants to know more..

John gets help!

Use of Java-1

Use of Java - 2

Use of Java - 3
1
6

John is convinced to learn Java
1
7

A Gift for John
1
8

An Android Phone
1
9

John is all set to learn Java
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0

What is Java?
• Java is a computer programming language that is
• Concurrent
• class-based
• object-oriented
• specifically designed to have as few implementation dependencies as
possible.
2
1

Where is Java Used?
• Java is used in various enterprise level application/frameworks all around the
world.
• Java is used:
– In over 850 million PCs as Java Runtime Environment
– To develop Android Applications
– To develop Hadoop Applications
– To develop business process management(BPM) tools.
– To develop webservers,application servers, etc.
• Java has been used to develop below frameworks:
– Hadoop
– Spring
– Hibernate
– Struts
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2

Java –Job, Demand and Experience Trends
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3

Languages before Java
• Before Java emerged as a programming language, there were many other
programming languages:
– C
– C++ (the dominant player in the trade)
– Visual Basics
– Python
• The primary goal was to replace C++:
– C++ does not provide efficient means for garbage collection
– No built in support for threads
– It gets complex when u want to develop a graphics richapplication
– C++ is not platform independent
– In C++ memory allocation and de-allocation has to be done by the
developer
2
4

History of Java
• Java was developed by James
Gosling in Sun Microsystems.
• It is a platform independent
programming language.
• This language was initially
named as OAK and later
renamed as JAVA.
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5

JavaVersions
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6

Features of JAVA

C++ : Platform Dependent
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9

Java : Platform Independent
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0

Features of Java
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1

Features of JAVA
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2

Features of JAVA
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3

Features of JAVA
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4

Features of JAVA
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5

Features of JAVA
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6

Features of JAVA
3

Features of JAVA
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8

Features of Java
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9

Questions
4
0
What is byte code?

Answer
4
1
Bytecode is an intermediate code which gets generated when a Java file is
compiled using a Javac compiler. After compilation .class file is generated
which contains the byte code. This code is platform independent.

Question
4
2
What is the advantage of executing parallel
threads/tasks at a time?

Answer
4
3
When many tasks/threads run at the same time, performance of the system
increases.

Bytecode and Java Virtual Machine (JVM)
• Java bytecode is the form of instructions that the Java Virtual Machine
executes.
• AJavaprogrammer need not understand bytecode at all.
• Java Virtual Machine (JVM)
– Runs the bytecode
– Makes Java platform independent
– Handles memory management
4
4

Java Memory Management
• C/C++ has pointers. User can
allocate memory to these
pointers.
• If the pointer is accessed
without allocating memory or
invalid pointer is accessed then
program crashes.
• These issues are removed from
Java as Java does not have
pointers. Complete memory
management ishandled by Java
itself.
4
5

Heap and Garbage Collector
• The memory area in JVM where objects are created is called Heap.
• Heap is divided into two parts. Young space and old space.
• The memory is freed during runtime by a special thread called Garbage
Collector.
• The Garbage Collector looks for objects which are no longer needed by
the program and destroysthem.
• All the newly allocated objects are created in young space. Once the
young space is full then garbage collector is called so that memory can
be released.
• If the object has lived for long in young space then they will be moved to
old space. Once the old space is full, garbage collector is called to
release the space in heap.
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6

Heap In side JVM
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7

Inside Heap
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8

Objects and References
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9

Garbage Collector
5
0

How Java Works?
5
1

Data Types
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2

Question
5
3
Why do you think we need byte, short and long datatypes when
int can be used?

Answer
5
4
‘byte’ takes 1 byte, ‘short’ takes 2 bytes and ‘int’ takes 4 bytes in
memory. If we know that the variable need not be very big then
‘short’ is fine as it reduces the memory consumption which inturn
increases the performance of the project.

Data Operations
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5

Required Software
• Required software for Java Programming
– »JDK 1.7 64 bit or 32 bit according to your machine.
• http://www.oracle.com/technetwork/java/javase/downloads/jd
k7-downloads-1880260.html
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6

Required Software
• Required software for Java Programming
– Eclipse J2EE version for 64 bit or 32 bit
according to your machine.
• https://www.eclipse.org/downloads/
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7

Select a workspace
5

Create a Project
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9

Create Class
6

My First Program
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1

Execute Java Program
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2

Main Method
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3

Programs for Data Types and Operations
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4

Choices in Real Life
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If..else Condition
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‘if’ Conditions
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If..else in Java
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if else in Java (Contd..)
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9

Program on if condition
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0

Repetitive task in Real Life
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1

Repetitive Tasks in Real life (contd..)
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2

Loops
7

Question
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4
What could be the advantage of using loops?

Answer
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5
The advantage of using loops is that, we can reduce code
repetition by placing the statements to be repeated within a loop.
As a result developer's effort will be very less.

for…Loop
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for…Loop Program
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while… Loop
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while…Loop Program
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do…while Loop
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while ..Loop Program
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1

Assignment – Data Type and Operation
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2

Assignment if..Condition
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3

Assignment for…Loop
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4

Assignment – while…loop
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5

Assignment do..while Loop
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Pre-work
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7

Thank You

Introduction to Java

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