Home > Articles

Overcoming Challenges in Mobile J2ME Development

Even if you're an experience J2SE/J2EE developer, to become a good mobile Java developer you'll need to understand the special characteristics of mobile devices, wireless networks, and mobile users. This sample book chapter explains the challenges in mobile application development and how to overcome them.
This chapter is from the book


  • Limited Device Hardware

  • Slow, Unreliable Networks

  • Pervasive Devices

  • Ubiquitous Integration

  • The Impatient User

J2ME allows desktop or enterprise Java developers to migrate their existing skills to build smart mobile applications for enterprises and consumers. Those skills include basic concepts of the Java language, APIs, and common design patterns. However, blind "skill transfer" from the desktop, server, or thin client world could do more harm than good. For example, although most AWT-based J2SE applications run on PersonalJava and J2ME Personal Profile without modification, porting them directly to mobile devices often results in unacceptable performance and very poor usability. To build successful smart mobile applications, developers must understand the special characteristics of mobile devices and networks.

As Java developers and architects, what should we know about the mobile development? How do we retrain ourselves for the new tasks? This last chapter of Part II, "End-to-End Enterprise Applications," answers those questions. We analyze challenges in mobile application development and discuss best practices to overcome them. Many of the solutions and tools we introduce in this chapter are discussed in further detail later in this book.

7.1 Limited Device Hardware

The most visible difference between the mobile and PC platforms is the difference in computing hardware. Today's PCs have much faster CPUs and far more memory and storage spaces than any mobile computing devices. Desktop and server developers can afford the luxury to write applications with bloated features (e.g., Microsoft Office); they also have access to rich productivity features provided by large, all-in-one frameworks (such as the J2SE platform itself). However, on mobile devices, it is a completely different story. With CPUs as slow as 20MHz and RAM as little as 100KB, we must carefully evaluate the features we need, thoroughly optimize our code, and live with limited framework support. In this section, we discuss how to cope with those challenges.

7.1.1 Lightweight Libraries

The most common mistake beginners make is the "golden hammer" anti-pattern: choosing the wrong technology for the task. In the Java world, software tools are often available as reusable objects in standard or third-party libraries. To choose the best libraries that support required application features at the minimum hardware cost is essential.

J2ME Foundation and Personal Profiles (as well as PersonalJava) are compatible with J2SE at the bytecode level and inherit a large subset of the J2SE core API. In theory, we can port J2SE libraries (e.g., XML processing, cryptography, messaging, and UI) directly to mobile devices. However, to do so would defeat the purpose of J2ME and result in slow and bloated applications that can be deployed only to the most expensive devices. In most cases, we should choose from lightweight library alternatives that are specifically designed for the mobile platform. Multiple vendors often compete in the same market. Each vendor offers a slightly different lightweight product with an emphasis on different features. Chapters 11 and 19 provide examples of how to compare and choose the best lightweight embedded database and cryptography toolkits for your projects.

CLDC and MIDP standard libraries are designed from the ground up as lightweight components. However, the need to select the right tools also applies to MIDP projects when it comes to third-party libraries. For a specific library, vendors often offer a version with J2SE-compatible APIs for larger MIDP devices (e.g., Symbian OS devices) and another extremely lightweight version that uses proprietary APIs. The latter often has a smaller memory footprint and better performance, but requires extra developer training and results in less portable applications. Examples of MIDP lightweight libraries include the PointBase MIDP relational database APIs (see Chapter 12, Section 12.1) and iBus//Mobile JMS client APIs (see Chapter 10, Section 10.3).

7.1.2 Reduce Application Footprint

Pervasive mobile devices have extremely limited memory and storage spaces, requiring us to minimize both the storage and runtime footprints of the application. Specific suggestions are as follows.

  • Optimize the packaging process: Even after carefully choosing the best lightweight library, we may still find that the application utilizes only part of the library. In the packaging process, we should include only the classes we actually use. We can do this manually for smaller libraries or use automatic tools bundled with some J2ME IDEs (such as the IBM WebSphere Studio Device Developer) for large libraries. If you want to further reduce the binary application size, you can use a bytecode obfuscator to replace long variable names and class names with shorter, cryptic ones.

  • Partition the application: Since the MIDP runtime loads classes only as needed, we can partition the application into separate parts to reduce the runtime footprint. For MIDP applications, the MIDlet suite can contain several relatively independent MIDlets.

Although the standard MIDP specification does not support shared libraries, some vendor-specific implementations do. An example is the BlackBerry Java Development Environment (JDE) for BlackBerry handheld devices. A shared library further reduces the overall footprint, since the library no longer needs to be duplicated and packaged in each application.

7.1.3 Minimize the Garbage Collector

One great advantage of Java is the built-in garbage collector that automatically frees memory space used by stale objects. This allows developers to focus on the core logic rather than on mundane details of memory management. As a result, Java developers are usually unconcerned about object creation. In fact, many popular Java design patterns promote the idea of creating more objects in exchange of more maintainable code. For example, in the Sun Smart Ticket (Chapter 5) sample application, the use of the MVC and facade patterns results in many objects that simply delegate the action to the next layer. To get a feel for this problem, just look into the numerous classes that implement the RemoteModel interface.

But on mobile devices, due to the small amount of available memory, the garbage collector must run more often. When the garbage collector runs, its thread takes up precious CPU cycles and slows down all other application processes. For effective J2ME applications, we need to minimize object creation and quickly dispose of objects that are no longer in use. Specific suggestions are as follows:

  • Carefully examine design patterns in early stages of the development cycle. For example, the screen flow-based approach demonstrated in the iFeedBack sample (Chapter 3) results in many fewer objects than a traditional MVC implementation.

  • Concisely reuse existing objects at the implementation level. For example, if a same button (e.g., the DONE button) appears in many screens, we should create it once and reuse it.

  • Use arrays and StringBuffers. Arrays are much faster and more memory efficient than collection objects. When we modify or concatenate strings, the immutable String objects result in a lot of intermediate objects. The StringBuffer is much more efficient.

  • Close network connections, file handlers, and Record Management System (RMS) record stores quickly after use. We need to look over the documentation carefully to find out all the close(), destroy(), and dispose() methods and use them judiciously. It is usually considered a best practice to place those methods in the finally block to make sure that the resources are released even if runtime exceptions are thrown.

    try {
      HttpConnection c =
        (HttpConnection) Connector.open("http://someurl");
      InputStream is = c.openInputStream ();
      // do something with the data
    } catch (Exception e) {
      // handle exceptions
    } finally {
      try {
        if ( c != null ) c.close();
        if ( is != null ) is.close();
      } catch (IOException ioe) { }
  • Free resources when using native libraries. In smart mobile applications, we sometimes need to access native libraries for better performance, restricted functionalities (e.g., to make a phone call), or simply native UI look and feel (e.g., the IBM SWT library for PocketPC). Native resources are not subject to garbage collection. It is important to follow proper instructions of the native libraries (and their Java wrapper classes) to free resources after use.

7.1.4 Use Mobile Portals

Smart mobile devices are getting more powerful every day. However, in complex enterprise environments, many tasks are still too resource-intensive for most mobile devices. In this case, a commonly used approach is to set up portal servers to which the mobile devices can delegate complex tasks. Mobile middleware portals bridge mobile clients to enterprise backend servers. The smart portal is much more than a proxy or a surrogate for mobile devices. The uses of mobile portals include the following.

  • Allow mobile clients to utilize multiple communication and messaging protocols. For example, mobile messaging servers described in Chapters 9 (Section 9.4) and 10 enable a wide range of devices over a wide range of networks to integrate into corporate messaging infrastructures.

  • Aggregate backend services and enable bundled services. For example, the Oracle9iAS Wireless server provides J2ME SDKs for Oracle's SQL database, push-based messaging, and location-based services. The BlackBerry Enterprise Server supports unified access to Microsoft Exchange-based or IBM Lotus Domino-based corporate information systems from BlackBerry MIDP devices (see Chapter 8, Section 8.6).

  • Provide simple mobile interfaces for powerful and sophisticated backend services. There are several notable examples:

    - The MapPoint facade described in Chapter 18, Section 18.2.2, shows how to build an easy-to-access interface for a complex backend Web service.

    - Database synchronization servers (Chapter 13) synchronize J2ME mobile databases with backend enterprise data sources using complex conflict resolution logic.

    - The Simplicity Enterprise Mobile Server supports simple, visual ways to build J2ME clients for legacy (mainframe) applications. (See Chapter 14, Section 14.3).

7.1.5 Use Design Patterns Judiciously

No design pattern is the silver bullet for every situation. For example, the powerful MVC and Facade patterns demonstrated in the Smart Ticket blueprint (Chapter 5) require several abstraction layers and are probably too heavy for simple applications. For simple applications, we can design the entire logic around screens, as we did in the iFeedBack example (Chapter 3).

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020