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Introduction to Java
--from 《Computing Static Slice for Java Programs》
Java is designed to meet the challenges of application development in the context
of heterogeneous, network-wide distributed environments. Paramount among these
challenges is secure delivery of applications that consume the minimum of system
resources, can run on any hardware and software platform, and can be extended
dynamically.
Java originated as part of a research project to develop advanced software for a
wide variety of network devices and embedded systems. The goal was to develop a
small, reliable, portable, distributed, real-time operating platform. When the project
started, C++ was the language of choice. But over time the difficulties encountered
with C++ grew to the point where the problems could best be addressed by creating
an entirely new language platform. Design and architecture decisions drew from a
variety of languages such as Eiffel, SmallTalk, Objective C, and Cedar/Mesa. The
result is a language platform that has proven ideal for developing secure, distributed,
network based end-user applications in environments ranging from network-
embedded devices to the World-Wide Web and the desktop.
The design requirements of Java are driven by the nature of the computing
environments in which software must be deployed.
The massive growth of the Internet and the World-Wide Web leads us to a
completely new way of looking at development and distribution of software. To live
in the world of electronic commerce and distribution, Java must enable the
development of secure, high performance, and highly robust applications on multiple
platforms in heterogeneous, distributed networks.
Operating on multiple platforms in heterogeneousnetworks invalidates the
traditional schemes of binary distribution, release, upgrade, patch, and so on. To
survive in this jungle, Java must be architecture neutral, portable, and dynamically
adaptable.
The Java system that emerged to meet these needs is simple, so it can be easily
programmed by most developers; familiar, so that current developers can easily learn
Java; object oriented, to take advantage of modern software development
methodologies and to fit into distributed client-server applications; multithreaded, for
high performance in applications that need to perform multiple concurrent activities,
such as multimedia; and interpreted, for maximum portability and dynamic
capabilities.
Together, the above requirements comprise quite a collection of buzzwords, so
let’ s examine some of them and their respective benefits before going on.
What’s completely new is the manner in which Java and its run-time system
have combined them to produce a flexible and powerful programming system..
Developing your applications using Java results in software that is portable
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