Learning Java 1 - Introduction to Java Basic

Learning Java - A Foundational Journey


Explain the structured programming paradigm

Explain the object-oriented programming paradigm

Explain the features of Java as a OOP language

Describe Java platform and its components

List the different editions of Java

Explain the evolution of Java Standard Edition (Java SE)

Describe the steps for downloading and installing Java Development Kit
(JDK)
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© Aptech Ltd. Introduction to Java/Session 1

Software Applications
• The solution for solving a problem in the field of
information technology is achieved by
developing software applications.
• A software application can be defined as a collection
of programs that are written in high-level
programming languages to solve a particular problem.
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
The most prominent use of computers is to solve problems quickly and
accurately.

The solution adopted to solve a problem is provided as a sequence of
instructions or specifications of activity which enables a user to achieve
the desired result.


Knowledge of Domain:
🞛 Plays an important role while developing software applications
🞛 Can be defined as field of business or technology to which a problem belongs
🞛 Figure shows development of software application as a solution for managing various operations in a
banking domain.
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
Programming Languages:
🞛 Development of software application is done using a programming language.
🞛 A programming language is used as a medium for communicating instructions to the
computer.
🞛 Programming language enforces a particular style of programming that is referred to
as a programming paradigm.
🞛 Two types of programming paradigm:
Structured
Programming
Paradigm
Object-oriented
Programming
Paradigm
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• In structured programming paradigm, the application development is decomposed
into a hierarchy of subprograms.
• The subprograms are referred to as procedures, functions, or modules in different
structured programming languages.
• Each subprogram is defined to perform a specific task.
• Some of structured programming languages are C, Pascal, and Cobol.

Figure displays bank application activities broken down into subprograms:
Structured Programming
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
Main disadvantage of structured programming
languages are as follows:
🞛 Data is shared globally between the
subprograms.
🞛 Efforts are spent on accomplishing the solution rather
than focusing on problem domain.

This often led to a software crisis, as the maintenance
cost of complex applications became high and
availability of reliable software was reduced.
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
Growing complexity of software required change in programming style.

Some features that were aimed are:
🞛 Development of reliable software at reduced cost.
🞛 Reduction in the maintenance cost.
🞛 Development of reusable software components.
🞛 Completion of software development with the specified time interval.

These features resulted in the evolution of object-oriented programming paradigm.

Software applications developed using object-oriented programming paradigm are:
🞛 Designed around data, rather than focusing only on functionalities.

Figure shows different activities involved in object-oriented software development:
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Object-oriented Analysis (OOA) phase determines
the functionality of the system.
Object-oriented Design (OOD) phases
determines the process of planning a system in
which objects interact with each other to solve a
software problem.
Object-oriented Programming (OOP) deals with
the actual implementation of the application.

Unified Modeling Language (UML) helps to create visual models in the
system.

The actual implementation of these visual models is done using an OOP
language.
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
An OOP language is based on certain principles that are as follows:
Object Represents an entity which possesses certain features and behaviors.
Class Is a template that is used to create objects of that class.
Abstraction Is a design technique that focuses only on the essential features of an entity for a specific problem domain.
Encapsulation Is a mechanism that combines data and implementation details into a single unit called class.
Inheritance
Enables the developer to extend and reuse the features of existing classes and create new classes. The new
classes are referred to as derived classes.
Polymorphism Is the ability of an object to respond to same message in different ways.
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
An object represents a real-world entity.

Any tangible or touchable entity in the real-world can be
described as an object.

Figure shows some real-world entities:

Each object has:
🞛 Characteristics – Defined as attributes, properties, or features describing
the object.
🞛 Actions – Defined as activities or operations performed by the
object.

Example of an object, Dog.
🞛 Properties – Breed, Color, and Age
🞛 Actions – Barking, Eating, and Running

The concept of objects in the real-world can be extended to the
programming
world where software ‘objects’ can be defined. 11


A software object has state and behavior.

‘State’ refers to object’s characteristics or attributes.

‘Behavior’ of the software object comprises its actions.

Following figure shows a software object, a Car with its state and behavior:

Advantages of using objects are as follows:
1
• They help to understand the real-world.
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• They map attributes and actions of real-world entities with state and behavior of software
objects.
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
In the real-world, several objects:
🞛 Have common state and behavior.
🞛 Can be grouped under a single class.
🞛 Example: All car objects have attributes, such as color, make, or model.

Class:
🞛 Can be defined that a class is a template or blueprint which defines the state and behavior for all
objects belonging to that class.
🞛 Following figure shows a car as a template and a Toyota car as an object or instance of the
class:
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
Class comprises fields and methods, collectively called as members.
🞛 Fields – Are variables that depict the state of objects.
🞛 Methods – Are functions that depict behavior of objects.

Following table shows the difference between a class and an object:
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Class Object
Class is a conceptual model Object is a real thing
Class describes an entity Object is the actual entity
Class consists of fields (data members) and
functions
Object is an instance of a class


It is one of the most popular OOP language.

It helps programmers to develop wide range of applications that can run on various
hardware and Operating System (OS).

It is also a platform that creates an environment for executing Java application.

It caters to small-scale to large-scale problems across the Internet.

Java applications are built on variety of platforms that range from:
🞛 Embedded devices to desktop applications
🞛 Web applications to mobile phones
🞛 Large business applications to supercomputers
15


The brief timeline of Java is depicted as follows:
Timeline of Java
Since James Gosling was the key member of the team that developed the language, he is known as the father of Java.
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Java Virtual Machine
(JVM)
17
• Programming languages, such as C
and C++, translate compiled code
into an executable binary code,
which is machine dependent. JVM
is an execution engine that creates
a platform independent execution
environment for executing Java
compiled code.
Java Runtime
Environment (JRE)
• JRE is also written as Java RTE. The
JRE is a set of software tools that
are used for developing Java
applications. It is used to provide
runtime environment. It is the
implementation of JVM.
Java Development Kit
(JDK)
• JDK is a binary software
development kit released by
Oracle Corporation as part of the
Java platform. It is an
implementation of Java and
distributed for various platforms,
such as Windows, Linux, Mac OS
X, and so on. JDK contains a
private JVM and a few other
resources such as an interpreter, a
compiler (javac), an archiver (jar),
a documentation generator
(Javadoc), and so on.

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
OpenJDK refers to a free and open-source implementation of Java.

Oracle JDK has had better performance than OpenJDK.

However, the performance of OpenJDK is growing.

Contributions of the OpenJDK community often outperform Oracle JDK.

Both OpenJDK and Oracle JDK are created and maintained currently by Oracle only.
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
Class Data Sharing (CDS) feature helps reduce the startup time and memory footprint
between multiple JVMs.

When you use the installer to install the Oracle JRE, the installer loads a default set of
classes from the system Java Archive (JAR) file into a private internal representation.

The memory for applications comprises two components namely, stack and heap. The
stack is an area in the memory that stores object references and method information.
The heap area of memory deals with dynamic memory allocations.

A portion of the shared archive on the same host is mapped as read-only and shared
among multiple JVM processes.

Application Class-Data Sharing
🞛 Allows application classes to be placed in a shared drive.
🞛 The common class metadata is shared across different Java processes.
🞛 AppCDS allows the built-in system class loader, built-in platform class loader, and custom class
loaders to load the archived classes.
20


To download the JDK, follow the link https://www.oracle.com/java/technologies/javase-
jdk15downloads.html.
21


To set the PATH variable permanently, add the full path of the jdk-15bin directory to
the PATH variable.

Typically, the full path is:
C:Program FilesJavajdk-15bin To set the PATH variable on Microsoft Windows:

Select Control Panel and then, System.

Click Advanced and then, Environment Variables.

Add the location of the bin folder of the JDK installation to the PATH variable in System
Variables.
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
What is Project Graal?
Project Graal was created by Oracle with the ultimate goal of improving JVM based languages performance to
match performance levels that native languages enjoy.

Just-In-Time Compiler - Is a form of dynamic compilation that combines the use of Ahead-Of-Time
(AOT) compilation and interpretation, and thus, has advantages and disadvantages from both
technologies.

Ahead-Of-Time Compilation - Main goal was to improve the start-up time of Java applications with
minimum impact to the application’s peak performance.

Interpretation - It is a process that interprets code and performs specified actions. There are
different ways an interpreter can work: it can parse the code and execute it directly, turn the code
into an intermediate representation and execute that, or it can execute code that has already been
pre-compiled.
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package
• A package defines a namespace that stores classes with similar
functionalities in them.
import
• The import keyword identifies the classes and packages that are
used in a Java class.
class
• The class keyword identifies a Java class. It precedes the name of
the class in the declaration.
• They represent the state of objects.
Variables
Methods
• Functions that represent some action to be performed on an
object.
Construc
tors
• Methods or functions that are invoked during the creation
of an object.
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
Basic requirements to write a Java program are as follows:
1. JDK 15 installed and configured on the system
2. A text editor
The text editor can be any simple editor included with the platforms. For example, the
Windows platform provides a simple text editor named Notepad.
To create, compile, and execute a Java program, perform following steps:
-
Create a Java program
-
Compile .java file
-
Build and execute Java program
Create a Java
program
Compile .java file
Build and execute
Java program
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
Step 1: Class Declaration

Step 2: Write the main method

Step 3: Write desired functionality

Step 4: Save the program
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
NetBeans is an open source written purely in Java.

It is a free and robust IDE that helps developers to create cross-platform
desktop, Web, and mobile applications using Java.

Some benefits of using NetBeans IDE for Java application development are
as follows:
- Builds IDE plug-in modules and supports rich client applications on the NetBeans
platform.
- Provides graphical user interface for building, compiling, debugging, and packaging of
applications.
- Provides simple and user-friendly IDE configuration.
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
The NetBeans IDE has following elements and views:
o
Menu Bar
o
Folders View
o
Components View
o
Coding and Design View
o
Output View
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
Comments are placed in a Java program source file.

They are used to document the Java program and are not compiled by the compiler.
They are added as remarks to make the program more readable for the user.

A comment usually describes the operations for better understanding of the code.
There are three styles of comments supported by Java namely, single-line, multi-line, and
Javadoc.
33


A single-line comment is used to document the functionality of a single line of code.

There are two ways of using single-line comments that are as follows:
Beginning-of-line comment - This type of comment can be placed before the code (on a
different line).
End-of-line comment - This type of comment is placed at the end of the code (on
the same line). Conventions for using single-line comments are as follows:
- Insert a space after the forward slashes.
- Capitalize the first letter of the first word.
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
A multi-line comment is a comment that spans multiple lines.

A multi-line comment starts with a forward slash and an asterisk (/*).

It ends with an asterisk and a forward slash (*/).

Anything that appears between these delimiters is considered to be a
comment.
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
A Javadoc comment is used to document public or protected classes,
attributes, and methods.

It starts with /** and ends with */.

Everything between the delimiters is a comment, even if it spans multiple
lines.

The javadoc command can be used for generating Javadoc comments.
36


The development of application software is performed using a programming language that enforces a
particular style of programming, also referred to as programming paradigm.

In structured programming paradigm, the application development is decomposed into a hierarchy of
subprograms.

In object-oriented programming paradigm, applications are designed around data, rather than focusing
only on the functionalities.

The main building blocks of an OOP language are classes and objects. An object represents a real-world
entity and a class is a conceptual model.

Java is an OOP language as well a platform used for developing applications that can be executed on
different platforms.

Hidden classes, Z Garbage Collector, Sealed classes, Records, and improved security with Edwards-
Curve Digital Signature algorithm are some of the new features in Java 15.

Apache NetBeans IDE version 12 and higher provide an integrated development environment to create,
compile, and execute Java programs.

The components of Java SE platform are JDK and JRE. JRE provides JVM and Java libraries that are used to
run a Java program. JDK includes the necessary development tools, runtime environment, and APIs for
creating Java programs.
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