Sun Microsystems 2 manual Robustness, Mechanisms Compared With Policies

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Robustness

In addition to providing the multitasking that users want, tasks have the following benefits:

■Fault containment - If a Java application crashes, then any problems caused by this crash are limited to the task. Applications running in other tasks are unaffected.

■Clean termination - When a Java application exits, it leaves the virtual machine in a consistent state. In the past, some have tried to run multiple Java applications in a single process by running the applications in separate threads within a single virtual machine. When applications share a virtual machine, it is impossible to guarantee that an application can exit cleanly, because objects might be left in an inconsistent state. In contrast, tasks can and do terminate cleanly.

Note that in MIDP, a Java application is a MIDlet suite. A MIDlet suite is one or more MIDlets in the same Java Archive (JAR) file. Each MIDlet suite, then, runs in its own task. The user interacts with one of the MIDlets in the MIDlet suite.

Mechanisms Compared With Policies

Mechanisms are actions that the system carries out, such as starting, pausing, and stopping a MIDlet. Policies are the system-wide decisions that device manufacturers and service providers make about when and how to use the available mechanisms. Policies take generic mechanisms and combine them into a predictable set of system behaviors.

The Java Wireless Client software provides both the necessary mechanisms for a complete application environment, such as mechanisms for managing competition for limited shared resources, and a default set of policies. For example, memory is a limited shared resource for which the Java Wireless Client software provides mechanisms and a few default policies. The mechanism is the allocation of heap memory. One default policy is to allow the applications to compete for available heap memory.

The default policies are useful, but device manufacturers and service providers are likely to need to tailor policies to their particular platforms. Devices of different capabilities might use different policies. Devices with different user interface styles might use different policies so that their Java applications interact with users in ways that match the native applications interactions. Because policy decisions are often intertwined with user interface style and user model decisions, the Java Wireless Client software enables the development of alternative policies.

Chapter 1 Introduction 3

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Contents Multitasking Guide Page Contents Glossary Index Code Samples Vi Multitasking Guide May Tables Viii Multitasking Guide May Before You Read This Guide PrefaceRelated Documentation How This Guide Is OrganizedAaBbCc123 Typographic Conventions Used in This GuideSun Welcomes Your Comments Accessing Sun Documentation OnlineIntroduction Multitasking Mechanisms Compared With Policies RobustnessMultitasking Guide May Multitasking Safety Multitask Safety and Multithread Safety Global and Static Data Singletons Code Example 2-1Native API for a Microwave Oven Multitasking Safety ExampleTypical usage of this API is shown in Code Example Multithread Safety Code Example 2-5Using the Locking Mechanism Multitask Safety Code Example 2-7Migrating Initialization to Native Code Establishing Per-Task Context Code Example 2-8Keeping State in Java Code Code Example 2-9Implementing the Native ncook Method Kniexport Knireturntypeint Multitasking Safety Multitasking Guide May Managing Native Resources Reservation Resource Management MechanismsLimit Revocation Default Resource Allocation PoliciesCustomization of Resource Allocation Policies Maximum number of tasks isolates allowed Managing Native Resources Multitasking Guide May Switching the Foreground MIDlet Other Multitasking IssuesDefault Policy Scheduling the CPUAlternative Policies and Their Implementations Default CPU Scheduling Policy Interrupting the User Default User Notification PoliciesGlossary Java Community ProcessTM Jcptm Glossary Sun Java Device Test Index Multitasking Guide May
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Sun Microsystems, founded in 1982, was a significant player in the computing industry, best known for its innovative technology solutions and workstations, particularly the Sun-4, which represented a key milestone in the company's history. The Sun-4 architecture, launched in 1987, utilized the SPARC (Scalable Processor Architecture) RISC processor, notable for its high performance and scalability.

One of the primary features of Sun Microsystems' platforms was their ability to efficiently handle multitasking and resource management, making them ideal for enterprise-level applications and development environments. Sun-4 workstations boasted impressive graphics capabilities with the addition of advanced graphical user interfaces, support for color displays, and the SUNVIEW windowing system, which enhanced user experience and productivity.

The Sun-4 systems also supported the SunOS operating system, which was based on UNIX. This operating system was engineered for stability and robustness, offering features like multiuser support, networked environments, and advanced security options. Moreover, SunOS provided seamless integration with various programming languages, including C and C++, facilitating software development that aligned with industry standards.

Another standout characteristic of Sun Microsystems was its commitment to open systems and standards. By providing developers with comprehensive tools and environments, such as the Standardized Application Programming Interface (API) and support for networking protocols, Sun facilitated interoperability among different computing platforms. The emphasis on open architecture also meant that customers could easily upgrade their systems without being locked into proprietary solutions.

Sun Microsystems was also ahead of its time with innovations in network computing. Their workstations were among the first to support network file systems and distributed computing concepts, enabling seamless data sharing across multiple systems. With the introduction of the Network File System (NFS), Sun revolutionized how data was accessed and managed across networks, which played a significant role in the evolving landscape of client-server computing.

In summary, the Sun Microsystems 2 and its successive innovations in workstation technology highlighted the company's forward-thinking approach. By integrating powerful performance with open systems, robust operating systems, and advanced networking capabilities, Sun laid the groundwork for modern computing, influencing various sectors from academia to enterprise solutions. Even after its acquisition by Oracle in 2010, the legacy of Sun Microsystems continues to be felt across the computing industry.
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