Tax Calculator Java - Features, JVM, UML, Implementation, NetBeans IDE

This article discusses the features of Java programming language, Java Virtual Machine, UML, implementation, and NetBeans IDE in the context of Tax Calculator Java. It covers topics like object-oriented programming, robustness, platform independence, multithreading, abstraction, encapsulation, inheritance, and polymorphism. The article also explains the use of try-catch blocks, if-else statements, and alert message dialog boxes for exception handling and error reporting. The article is relevant for students studying Java programming and finance courses.

Running head: TAX CALCULATOR JAVA
Tax Calculator Java
Name of the student:
Name of the University:
Author note:

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Table of Contents
LO1............................................................................................................................................2
1.1 Features of Java................................................................................................................2
1.2 Java Virtual Machine.......................................................................................................6
LO2............................................................................................................................................7
2.1 UML and Use Case..........................................................................................................7
2.2 Components and File Structure........................................................................................8
LO3............................................................................................................................................8
3.1 Implementation................................................................................................................8
3.2 Design Explanations.......................................................................................................11
3.4 Exception Handling and Error Reporting......................................................................12
3.5 NetBeans IDE.................................................................................................................13
LO4..........................................................................................................................................15
4.1 & 4.2 Testing and Analysis............................................................................................15
4.3 User Review...................................................................................................................17
4.5 Documentation...............................................................................................................19

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LO1
1.1 Features of Java
Java programming language has been developed by Sun Microsystem, initiated by
James Gosling in 1995 as a core component of Sun Microsystems, now owned by Oracle,
Java platform (Java 1.0 J2SE). There has been various updates in the Java. The latest release
of the Java Standard Edition is Java SE 9. Java has able to change the internet. An update in
Java has been applet that helped in connecting Java to the internet. An applet is a java
program that has been designed to transmit over the internet and execute a java compatible
web browser. Applet can be downloaded on the demand of user and used for displaying data
provided by the server. However, security and portability have been major issues in a
programming language. Therefore, java has been able to mitigate these issues by developing
byte code. A byte code is a highly optimized set of instruction that is executed by the Java
Runtime machine or Java Virtual Machine (JVM). JVM has been designed as an interpreter
for byte code. Following are the features of Java (Sebesta 2016):
Object Oriented Programming: Object oriented programming (OOP) has been the
core of the Java. OOP has been integral part if the Java. Therefore, the basic principles of the
OOP need to be understood before coding a Java program (Schmidt et al. 2013). The basic
features of the Object Oriented Programming have been mentioned below:
Robust: Robust refers strength of the object. Java is a robust program language as it
uses a strong memory management. There has been a lack of pointers that helps in avoiding
security problems. There has been an automatic garbage collection in Java that helps in
running on the Java Virtual Machine for getting rid of the objects and not being used by Java
application. There have been an exception handling and type checking mechanism in Java.
These [points have been helping in making Java a robust program.

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Platform Independent: Java is a platform independent program as it helps in executing
different languages including C, C++ and other languages that are compiled into platform
specific machines. A platform is a hardware or software environment on which a program
runs. Java helps in providing software-based platform. The platform of Java has been
different from other platforms as it runs on the top of other hardware based platforms. It
include two components inckudidng Runtime Environment and Application Programing
Interface (API). Java codes are compatible to run in various other platforms including
Windows, Linux, Sun Solaris and Mac/OS. Java code can be compiled by the compiler and
transformed into byte code (Morelli and Walde 2012). This byte code has been a platform
independent code as it can be complied over multiple platforms.
Multithreaded: A threaded is a separate program that execute concurrently. Java
programs deals with many tasks at a time by defining multiple threads (Kika and Greca
2013). The major benefit of multi-threading has been consumption of low memory and it
does not occupy memory for each and every thread. It shares a common memory space for
every thread. Threads have been important component for web applications and multimedia
(Czajkowski and Daynàs 2012).
Following are the principles of OOP:
Abstraction: Abstraction has been an essential element of object-oriented programing.
Abstraction can be used for minimizing complexity of any system. For example, people do
not think about the internal systems of a car. They only deals car as an object with its unique
behavior. They do not think about the way it operate including transmission and engine
operations. Similar to those, abstraction deals with the unique behavior of codes and
programs rather focusing on how it is working. Hierarchical abstractions of complex systems
are applied on computer programs. Data transferred from traditional process oriented

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program can be modified into abstraction and objects. A series of process steps have been
collected for messages between these objects. These objects used to describes its own unique
behavior and functionalities. Object oriented concepts have been related to the human
behavior in the real world. Therefore, concept of abstraction has been related to the
behavioral aspects of human beings in the real world. Abstraction help in minimizing the
complexity of programs and systems from user point of view.
Encapsulation: It is the mechanism that helps in binding codes together and
manipulate data. Encapsulation acts as protective layer for codes and data for being used
arbitrarily accessed by other set of codes in the program. In Java, basis of encapsulation is the
class. Class is defined as behavior and structure that is shared with various objects. Each
variable in the program can be marked as public and private. The public interface of class
refers everything that an external user need to know about the program (Koscielny et al.
2014). The private methods and data can only be accessed by member of the class.
Therefore, codes that are outside of that class, cannot access a private method. This help in
ensuring security to the data and codes.
class Account {
private int account_number;
private int account_balance;
public void show Data() {
//code to show data
}
public void deposit(int a) {
if (a < 0) {
//show error
} else
account_balance = account_balance + a;
}

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}
Inheritance: Inheritance is a process by which an object helps in acquiring properties
of another object. It has been one of the most important principles of the OOP. A hierarchical
order is followed in this principle. Inheritance interacts with encapsulation for providing
secured level of hierarchy in the program. Inheritance helps in minimizing the space
complexity of program and encourages reusability of codes. A platform is a hardware or
software environment on which a program runs. Java helps in providing software-based
platform. Java does not support multiple inheritance.
Polymorphism: Polymorphism refers to the mechanism of allowing one interface to
be used for a general class of actions. Polymorphism helps in designing a generic interface
for a group of related activities. Therefore, it reduces complexity of programs by allowing
same interface to be used by specify a general class of action.
class Shape{
void draw(){System.out.println("drawing...");}
}
class Rectangle extends Shape{
void draw(){System.out.println("drawing rectangle...");}
}
class Circle extends Shape{
void draw(){System.out.println("drawing circle...");}
}
class Triangle extends Shape{
void draw(){System.out.println("drawing triangle...");}
}
class TestPolymorphism2{
public static void main(String args[]){
Shape s;
s=new Rectangle();

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s.draw();
s=new Circle();
s.draw();
s=new Triangle();
s.draw();
}
}
1.2 Java Virtual Machine
Java programs can be executed in any platform and compiled in Java programming
source. IT helps in generating Byte code of the program. Byte code is a Java compiler that
helps in generating platform independency property. Therefore, this byte code can be run in
any platform. It is executed by a program, named as Java Virtual Machine that is the main
element of the Java Runtime Environment. The platform of Java has been different from
other platforms as it runs on the top of other hardware based platforms. The source file of the
Java program has an extension of .java and the byte code file has been generated by Java
compiler. There are multiple classes in the java program that needs to be compiled in the
JVM. Therefore, Java plays an important role in the Java.

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LO2
2.1 UML and Use Case
Fig 1. Use Case Diagram

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Fig 2. UML Class Diagram
2.2 Components and File Structure
 Java Project Name: Finance
 Package Name: finance
 Home Page Form: TaxCalculator.java; TaxCalculator.form
 Tax Output Form: Display.java, Display.form
Compilation File Structure:
Finance => finance => src => TaxCalculator.java
The file mentioned above needs to be compiled and executed in order to run the
program successfully.
LO3
3.1 Implementation
Home Page form (TaxCalculator class)

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Output page form (Display class)
Parent class (Product)

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Child Class 1 (Selling Product)
Child Class 2 (Sample Product)

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3.2 Design Explanations
GUI Justifications
The classes that have been used in this project are meant to solely suffice to the needs
of the program. The GUI form classes have been specifically designed and developed for
inputs and output requirements of the program. The input form’s GUI or the graphical user
interface has been so designed to allow the users to enter all the necessary information that
will be required by the Tax Calculator to calculate the appropriate tax results for the
particular product entries.
The home page or the Tax Calculator form page is supposed to greet the users into the
program. This page provides a form with input areas for the type of product, the initial price
and the shipping cost of the concerned product. The type of the product can be selected by the
user using a Radio Button input. This takes the chances of erroneous product-type inputs by
the user, which could have otherwise been an integration problem for the system. The user is
presented with two clickable options, Selling Product and Sample Product, of which the user
can choose only one and the same will get saved for the particular entry.
The display page is the output form for the application. This form is used to represent
the bill page of the software where the tax results are calculated and displayed along with all
the other necessary details of the finance simulator. The display areas are so programmed, to
display the ‘£’ symbol to symbolize the currency being dealt with.
Choice of Classes
The Product class has been chosen as the parent class for the program. This class has
two other child classes and they exhibit the Inheritance feature of Java’s object oriented
programming. The Product class has all the data attributes and the necessary functions. These
data attributes and methods are common for all the child classes namely the Selling Product

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and the Sample Product, however, the methods are overridden when used in the child classes.
The parent class methods just has a mere definition and performs no special functionality.
The child classes inherit these functions and model them as per their own requirements
keeping the overall structure similar. This is called polymorphism in the language of Object
Oriented Programming, where a method or other instances can be used for different purposes
under the same name and definition. The java classes for the forms checks for the user input
validations and creates instances of the respective Product class object (Selling Product or the
Sample Product).
3.4 Exception Handling and Error Reporting
Try catch blocks have been used to handle invalid inputs in the form page where the
user is supposed to enter data. Also, in cases where manual exceptions like negative number
inputs or null inputs are to be checked, if-else conditional blocks are used with respective
‘throw new Exception’ syntax.
Error reporting is primarily done using the Alert Message Dialog boxes. The user will
require to click on an OK option every time the error is popped up and need to go back to fix
the issue. Below is the code snippet that highlights the exception and error handling
implementation using Try-Catch and If-else statements.

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3.5 NetBeans IDE
The application has been developed in the NET Beans IDE because IDEs have been helpful
in writing codes and managing files easily. It has been helpful for creating derived classes for
the existing classes. It has been automatically generating basic functionality for class
including constructor. Therefore, for retrieving the class method, override a base class
method and the basic structure of the function.
Works Out of the Box
It has been achieved by downloading and installing NetBeans. The downloaded file has been
of small size. All IDE tools and features have been totally integrated and no requirement of
plug-in and launch IDE.
Free and Open Source
The utilization of NetBeans IDE has been different and open source for thousands of users
and helping for contributing. There have been various discussion on the NetBeans lists.
Connected Developer
NetBeans is a tool for choice for teams working together in a collaborative environment. This
can be used for creating attractive websites using Jira and Bugzilla, and integrate with various
tools and interface of IDE.
Powerful GUI Builder
The GUI Builder has been supporting a sophisticated simplified Swing Application
Framework and Beans Binding. Now GUIs can be built in a natural way.
Support for Java Standards and Platforms

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The IDE provides end-to-end solutions for all Java development platforms including the
latest Java standards.
There has been various preprocessor blocks that can help in reading handle fragmentation
issues. There has been various support for Java Mobility development that can helpful under
Java development tools.
Java Enterprise Edition (EE) 9 support: This has been a free, open-source IDE for supporting
Java EE 9 specifications. This help in supporting different categories and tools for java
development in the programs. This has been easy and smooth for use in the programs
(Heffelfinger 2015). The use of the NetBeans have been helping in creating proper
functionality of website in the Java.

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LO4
4.1 & 4.2 Testing and Analysis
To test Input Expected
Output
Actual Output Analysis
System provides proper
output or tax and VAT
for Selling Products.
Selling
Product;
Price: 100
Shipping:
50
Import Tax:
3.0
VAT: 30.60
Total: 33.60
Success
System provides proper
output or tax and VAT
for Sample Products with
price below 135.
Sample
Product;
Price: 100
Shipping:
50
Import Tax:
0
VAT: 0
Total: 0
Success
System provides proper
output or tax and VAT
for Sample Products with
price above 135.
Selling
Product;
Price: 200
Shipping:
50
Import Tax:
2.00
VAT: 23.40
Total: 25.40
Partial Success
The output result is
mathematically equal
to what is expected,
however it does not
suffice to the round-off
rule, and hence the test
fails to succeed as a

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whole.
Check for invalid
character inputs
Initial
Price:
“asd”
Error
Reporting
Success
Check for null inputs Empty
inputs
Error
Reporting
Success
Check for No product
type selection
Select no
type
Error
Reporting
Success

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4.3 User Review
Two different users have been asked to review the usability and functionality features
of the application and their feedbacks have been recorded as below:
User 1:
Name: John Doe
Used and tested for: 2 weeks
Purpose: Back-office financial management
1. Are you satisfied with the overall application?
o Yes
o No
Reason: ______________________________________
 Somewhat
2. Are you satisfied with the User Interface?
 Yes
o No
Reason: ______________________________________
3. Are you satisfied with the functionalities provided?
o Yes
 No
Reason: The app should also allow us to know the final cost of the product
after the tax amounts have been added.

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User 2:
Name: Jane Doe
Used and tested for: 1 week
Purpose: Goods import business
1. Are you satisfied with the overall application?
 Yes
o No
Reason: ______________________________________
o Somewhat
2. Are you satisfied with the User Interface?
o Yes
 No
Reason: No back button. No Exit button. No button to reset data in insert page.
3. Are you satisfied with the functionalities provided?
o Yes
 No
Reason: There should be a page with more information about the system and also
allow the users to choose different tax policies and currencies.
From the above reviews, it can hence be concluded that there are a couple of
enhancements that can be made to the GUI. This includes a button that will help the users to
navigate between the pages using a back button and also allow the users to resent the data
entered. Also, the app should in the future support multi-currency support.

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4.5 Documentation
The project can be compiled by opening the project in the NetBeans IDE. Then, it is
necessary to click on the Build project option and set the TaxCalculator form class for
execution. Furthermore, on clicking the execute button (The green triangle), the program will
be executed.

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References
Sebesta, R.W., 2016. Concepts of programming languages.
Schmidt, D.C., Stal, M., Rohnert, H. and Buschmann, F., 2013. Pattern-Oriented Software
Architecture, Patterns for Concurrent and Networked Objects (Vol. 2). John Wiley & Sons.
Morelli, R. and Walde, R., 2012. Java, Java, Java: Object-Oriented Problem Solving.
Pearson Education, Inc.
Gaddis, T., Mukherjee, S. and Bhattacherjee, A.K., 2013. Starting out with Java: From
control structures through objects. Pearson.
Koscielny, J., Holthusen, S., Schaefer, I., Schulze, S., Bettini, L. and Damiani, F., 2014,
September. DeltaJ 1.5: delta-oriented programming for Java 1.5. In Proceedings of the 2014
International Conference on Principles and Practices of Programming on the Java platform:
Virtual machines, Languages, and Tools (pp. 63-74). ACM.
Czajkowski, G. and Daynàs, L., 2012. Multitasking without compromise: a virtual machine
evolution. ACM SIGPLAN Notices, 47(4a), pp.60-73.
Kika, A. and Greca, S., 2013. Multithreading image processing in single-core and multi-core
CPU using Java. International Journal of advanced computer science and applications, 4(9).
Heffelfinger, D.R., 2015. Java EE 7 Development with NetBeans 8. Packt Publishing Ltd.