Welcome!

Java IoT Authors: Paul Simmons, Liz McMillan, Yeshim Deniz, Pat Romanski, Elizabeth White

Related Topics: Java IoT, Microservices Expo

Java IoT: Book Excerpt

How to Get Started with Java and NetBeans

Book Excerpt: Essential Java Skills (Part 1)

When Sun's developers created Java, they tried to keep the syntax for Java similar to the syntax for C++ so it would be easy for C++ programmers to learn Java. In addition, they designed Java so its applications can be run on any computer platform. In contrast, C++ needs to have a specific compiler for each platform. Java was also designed to automatically handle many operations involving the creation and destruction of memory. This is a key reason why it's easier to develop programs and write bug-free code with Java than with C++. To provide these features, the developers of Java had to sacrifice some speed (or performance) when compared to C++. For many types of applications, however, Java's relative slowness is not an issue.

Microsoft's Visual C# language is similar to Java in many ways. Like Java, C# uses a syntax that's similar to C++ and that automatically handles memory operations. However, in practice, C# code only runs on Windows. Because of that, C# is a good choice for developing applications for a Windows-only environment. However, Java is a better choice if you need to develop crossplatform applications.

Applications, Applets, and Servlets
Figure 1 describes the three types of programs that you can create with Java. First, you can use Java to create applications that run directly on your computer. These are also known as desktop applications.

When you create these desktop applications, you can use a graphical user interface (GUI) to get user input and perform a calculation as shown at the top left of this figure. In chapter 15, you'll learn how to create these types of applications. Until then, you'll learn how to create another type of desktop application known as a console application. This type of application runs in the console, or command prompt, that's available from your operating system. An example of a console application is shown at the top right of this figure.

One of the unique characteristics of Java is that you can use it to create a special type of web-based application known as an applet. For instance, this figure shows an applet that works the same way as the applications above it. The main difference between an application and an applet is that an applet can be stored in an HTML page and can run inside a Java-enabled browser. As a result, you can distribute applets via the Internet or an intranet. In chapter 17, you'll learn how to create and deploy applets.

Although applets can be useful for creating a complex user interface within a browser, they have their limitations. First, you usually need to install a plug-in on each client machine, which isn't ideal for some types of applications. Second, since an applet runs within a browser on the client, it's not ideal for working with resources that run on the server, such as enterprise databases.

To provide access to enterprise databases, many developers use Java EE to create applications that are based on servlets. A servlet is a special type of Java application that runs on the server and can be called by a client, which is usually a web browser. This is also illustrated in this figure. Here, you can see that the servlet works much the same way as the applet. The main difference is that the code for the application runs on the server.

When a web browser calls a servlet, the servlet performs its task and returns the result to the browser, typically in the form of an HTML page. For example, suppose a browser requests a servlet that displays all unprocessed invoices that are stored in a database. Then, when the servlet is executed, it reads data from the database, formats that data within an HTML page, and returns the HTML page to the browser.

When you create a servlet-based application like the one shown here, all the processing takes place on the server and only HTML is returned to the browser. That means that anyone with an Internet or intranet connection, a web browser, and adequate security clearance can access and run a servlet-based application. Because of that, you don't need to install any special software on the client. To make it easy to store the results of a servlet within an HTML page, the Java EE specification provides for JavaServer Pages (JSPs). Most developers use JSPs together with servlets when developing server-side Java applications.

Although servlets and JSPs aren't presented in this book, we cover this topic in a companion book, Murach's Java Servlets and JSP. For more information about this book, please visit our web site at www.murach.com.

A GUI application and a console application

An applet

A servlet

Figure 1: Applications, applets, and servlets

The Code for the Console Version of the Future Value Application
To give you an idea of how the code for a Java application works, Figure 2 presents the code for the console version of the Future Value application that you saw in figure 1-2.

If you have experience with other programming languages, you may be able to understand much of this code already. If not, don't worry! You'll learn how all of this code works in the next few chapters. For now, here's a brief explanation of this code.

Most of the code for this application is stored in a class named FutureValueApp. This class begins with an opening brace ({) and ends with a closing brace (}). Within this class, two methods are defined. These methods also begin with an opening brace and end with a closing brace, and they are indented to clearly show that they are contained within the class.

The first method, named main, is the main method for the application. The code within this method is executed automatically when you run the application. In this case, the code displays the data the user sees on the console, accepts the data the user enters at the console, and calculates the future value.

The second method is named calculateFutureValue. This method is called from the main method and calculates the future value based on the data the user enters.

The code for the Future Value application

import java.util.Scanner;
import java.text.NumberFormat;
public class FutureValueApp
{
public static void main(String[] args)
{
System.out.println("\nWelcome to the Future Value Calculator\n");
Scanner sc = new Scanner(System.in);
String choice = "y";
while (choice.equalsIgnoreCase("y"))
{
// get the input from the user
System.out.print("Enter monthly investment: ");
double monthlyInvestment = sc.nextDouble();
System.out.print("Enter yearly interest rate: ");
double interestRate = sc.nextDouble();
System.out.print("Enter number of years: ");
int years = sc.nextInt();
// calculate the future value
double monthlyInterestRate = interestRate/12/100;
int months = years * 12;
double futureValue = calculateFutureValue(
monthlyInvestment, monthlyInterestRate, months);
// format and display the result
NumberFormat currency = NumberFormat.getCurrencyInstance();
System.out.println("Future value: " +
currency.format(futureValue) + "\n");
// see if the user wants to continue
System.out.print("Continue? (y/n): ");
choice = sc.next();
System.out.println();
}
}
private static double calculateFutureValue(double monthlyInvestment,
double monthlyInterestRate, int months)
{
double futureValue = 0;
for (int i = 1; i <= months; i++)
futureValue = (futureValue + monthlyInvestment) *
(1 + monthlyInterestRate);
return futureValue;
}
}

Figure 2: The code for the console version of the Future Value application

How Java Compiles and Interprets Code
When you develop a Java application, you create one or more classes. For each class, you write the Java statements that direct the operation of the class. Then, you use a Java tool to translate the Java statements into instructions that can be run by the computer. This process is illustrated in Figure 3.

To start, you enter and edit the Java source code for a class. These are the Java statements like the ones you saw in Figure 2 that tell the application what to do. Then, you use the Java compiler to compile the source code into a format known as Java bytecodes. At this point, the bytecodes can be run on any platform that has a Java interpreter to interpret (or translate) the Java bytecodes into code that can be understood by the underlying operating system.

Since Java interpreters are available for all major operating systems, you can run Java on most platforms. This is what gives Java applications their platform independence. In contrast, C++ requires a specific compiler for each type of platform that its programs are going to run on. When a platform has a Java interpreter installed on it, it can be considered an implementation of a Java virtual machine (JVM).

In addition, most modern web browsers can be Java enabled. This allows applets, which are bytecodes that are downloaded from the Internet or an intranet, to run within a web browser. To make this work, Sun developed (and Oracle now maintains) the Java Plug-in. This piece of software is similar to other browser plug-ins such as Apple QuickTime. It allows the browser to run the current version of the Java interpreter.

Figure 3: How Java compiles and interprets Code Description

  • When you develop a Java application, you develop one or more classes.
  • You can use a Java IDE or any text editor to create, edit, and save the source code for a Java class. Source code files have the java extension.
  • The Java compiler translates Java source code into a platform-independent format known as Java bytecodes. Files that contain Java bytecodes have the class extension.
  • The Java interpreter executes Java bytecodes. Since Java interpreters exist for all major operating systems, Java bytecodes can be run on most platforms. A Java interpreter is an implementation of a Java virtual machine (JVM).
  • Most modern web browsers can be Java enabled. This lets applets run within these browsers. Oracle provides a tool known as the Java Plug-in that allows you to specify the version of the Java interpreter that you want to use.

•   •   •

This excerpt is from the book Murach's Java Programming by Joel Murach: http://www.murach.com/books/javp/index.htm

More Stories By Joel Murach

Joel Murach has been writing and editing books about computer programming for over 10 years. During that time, he has written extensively on a wide range of Java, .NET, web, and database technologies. When he's not programming or writing books about programming, he can be found surfing or writing music.

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@ThingsExpo Stories
In his Opening Keynote at 21st Cloud Expo, John Considine, General Manager of IBM Cloud Infrastructure, led attendees through the exciting evolution of the cloud. He looked at this major disruption from the perspective of technology, business models, and what this means for enterprises of all sizes. John Considine is General Manager of Cloud Infrastructure Services at IBM. In that role he is responsible for leading IBM’s public cloud infrastructure including strategy, development, and offering m...
From 2013, NTT Communications has been providing cPaaS service, SkyWay. Its customer’s expectations for leveraging WebRTC technology are not only typical real-time communication use cases such as Web conference, remote education, but also IoT use cases such as remote camera monitoring, smart-glass, and robotic. Because of this, NTT Communications has numerous IoT business use-cases that its customers are developing on top of PaaS. WebRTC will lead IoT businesses to be more innovative and address...
Rodrigo Coutinho is part of OutSystems' founders' team and currently the Head of Product Design. He provides a cross-functional role where he supports Product Management in defining the positioning and direction of the Agile Platform, while at the same time promoting model-based development and new techniques to deliver applications in the cloud.
Business professionals no longer wonder if they'll migrate to the cloud; it's now a matter of when. The cloud environment has proved to be a major force in transitioning to an agile business model that enables quick decisions and fast implementation that solidify customer relationships. And when the cloud is combined with the power of cognitive computing, it drives innovation and transformation that achieves astounding competitive advantage.
IoT is rapidly becoming mainstream as more and more investments are made into the platforms and technology. As this movement continues to expand and gain momentum it creates a massive wall of noise that can be difficult to sift through. Unfortunately, this inevitably makes IoT less approachable for people to get started with and can hamper efforts to integrate this key technology into your own portfolio. There are so many connected products already in place today with many hundreds more on the h...
In his session at Cloud Expo, Alan Winters, U.S. Head of Business Development at MobiDev, presented a success story of an entrepreneur who has both suffered through and benefited from offshore development across multiple businesses: The smart choice, or how to select the right offshore development partner Warning signs, or how to minimize chances of making the wrong choice Collaboration, or how to establish the most effective work processes Budget control, or how to maximize project result...
Personalization has long been the holy grail of marketing. Simply stated, communicate the most relevant offer to the right person and you will increase sales. To achieve this, you must understand the individual. Consequently, digital marketers developed many ways to gather and leverage customer information to deliver targeted experiences. In his session at @ThingsExpo, Lou Casal, Founder and Principal Consultant at Practicala, discussed how the Internet of Things (IoT) has accelerated our abilit...
In his keynote at 19th Cloud Expo, Sheng Liang, co-founder and CEO of Rancher Labs, discussed the technological advances and new business opportunities created by the rapid adoption of containers. With the success of Amazon Web Services (AWS) and various open source technologies used to build private clouds, cloud computing has become an essential component of IT strategy. However, users continue to face challenges in implementing clouds, as older technologies evolve and newer ones like Docker c...
Data is the fuel that drives the machine learning algorithmic engines and ultimately provides the business value. In his session at Cloud Expo, Ed Featherston, a director and senior enterprise architect at Collaborative Consulting, discussed the key considerations around quality, volume, timeliness, and pedigree that must be dealt with in order to properly fuel that engine.
No hype cycles or predictions of zillions of things here. IoT is big. You get it. You know your business and have great ideas for a business transformation strategy. What comes next? Time to make it happen. In his session at @ThingsExpo, Jay Mason, Associate Partner at M&S Consulting, presented a step-by-step plan to develop your technology implementation strategy. He discussed the evaluation of communication standards and IoT messaging protocols, data analytics considerations, edge-to-cloud tec...
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life settl...
In his session at @ThingsExpo, Dr. Robert Cohen, an economist and senior fellow at the Economic Strategy Institute, presented the findings of a series of six detailed case studies of how large corporations are implementing IoT. The session explored how IoT has improved their economic performance, had major impacts on business models and resulted in impressive ROIs. The companies covered span manufacturing and services firms. He also explored servicification, how manufacturing firms shift from se...
IoT is at the core or many Digital Transformation initiatives with the goal of re-inventing a company's business model. We all agree that collecting relevant IoT data will result in massive amounts of data needing to be stored. However, with the rapid development of IoT devices and ongoing business model transformation, we are not able to predict the volume and growth of IoT data. And with the lack of IoT history, traditional methods of IT and infrastructure planning based on the past do not app...
Organizations planning enterprise data center consolidation and modernization projects are faced with a challenging, costly reality. Requirements to deploy modern, cloud-native applications simultaneously with traditional client/server applications are almost impossible to achieve with hardware-centric enterprise infrastructure. Compute and network infrastructure are fast moving down a software-defined path, but storage has been a laggard. Until now.
Digital Transformation is much more than a buzzword. The radical shift to digital mechanisms for almost every process is evident across all industries and verticals. This is often especially true in financial services, where the legacy environment is many times unable to keep up with the rapidly shifting demands of the consumer. The constant pressure to provide complete, omnichannel delivery of customer-facing solutions to meet both regulatory and customer demands is putting enormous pressure on...
The best way to leverage your CloudEXPO | DXWorldEXPO presence as a sponsor and exhibitor is to plan your news announcements around our events. The press covering CloudEXPO | DXWorldEXPO will have access to these releases and will amplify your news announcements. More than two dozen Cloud companies either set deals at our shows or have announced their mergers and acquisitions at CloudEXPO. Product announcements during our show provide your company with the most reach through our targeted audienc...
DXWorldEXPO LLC announced today that All in Mobile, a mobile app development company from Poland, will exhibit at the 22nd International CloudEXPO | DXWorldEXPO. All In Mobile is a mobile app development company from Poland. Since 2014, they maintain passion for developing mobile applications for enterprises and startups worldwide.
"Akvelon is a software development company and we also provide consultancy services to folks who are looking to scale or accelerate their engineering roadmaps," explained Jeremiah Mothersell, Marketing Manager at Akvelon, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
JETRO showcased Japan Digital Transformation Pavilion at SYS-CON's 21st International Cloud Expo® at the Santa Clara Convention Center in Santa Clara, CA. The Japan External Trade Organization (JETRO) is a non-profit organization that provides business support services to companies expanding to Japan. With the support of JETRO's dedicated staff, clients can incorporate their business; receive visa, immigration, and HR support; find dedicated office space; identify local government subsidies; get...
"We view the cloud not as a specific technology but as a way of doing business and that way of doing business is transforming the way software, infrastructure and services are being delivered to business," explained Matthew Rosen, CEO and Director at Fusion, in this SYS-CON.tv interview at 18th Cloud Expo (http://www.CloudComputingExpo.com), held June 7-9 at the Javits Center in New York City, NY.