JAVA介绍
作者：Martin Ngobye.
出处：Computing Static Slice for Java Programs
Java是被设计用来解决在上下文分布式的异构网络中应用程序开发的问题。在这些复杂问题中，首要的是安全发布应用程序、消耗最小的系统资源、可以在任何硬件和软件平台上运行以及被动态地扩展。
Java最初是作为研发方案的一部分而开发的，这个研究方案是为了给广阔多样的网络设备和嵌入式系统开发高级的软件。目标是开发一个小巧的、可靠性高的、可移植的、分布式的、实时的操作系统平台。当这个方案开始的时候，C++是精选的语言，但是过了一段时间，用C++语言遇到的困难也随之增长，解决这些问题最好的办法是创造一个全新的语言平台。设计和体系结构的决定汲取了多种语言，例如Eiffel、 SmallTalk,、Objective C以及 Cedar/Mesa。结果证明这个语言平台是理想的，对于开发一个可靠性高的、可移植的、分布式的、基于终端用户网络的应用程序在多种环境中广泛搜索从嵌入网络的设备到万维网和桌上型电脑。
Java的需求设计通过自然状态的，在软件必须被配置的处理环境中被推动的。
因特网和万维网的巨大发展导致我们完全地以新的情形着眼于开发和发行软件。对于全球电子化的商业和销售发行的存在，Java必须使安全的，高性能的和非常健壮的应用程序在多平台异构的，分布式的网络中开发。
在异构的网络中，多平台上运行会使传统配置的二进制发送、释放、更新、补丁等等无效。为了在这些问题中幸存下来，Java必须是体系结构中立的、可移植的以及可以被动态的修改。
为满足以上的需求而开发的Java系统是简单的，所以它能够被绝大多数的程序员进行编程；熟悉的，所以当前的程序员学习Java语言是简单的；面向对象的，为了利用现代的软件开发方法学和适合分布式的客户机/服务器应用程序；多线程的，为了高性能在应用程序中需要执行多个并发的活动,例如多媒体；解释的，为了最大极限的可移植和动态的容量。
同时，以上的需求完全是由收集的时髦词语组成的，所以在开始
以前让我们来查看它们中的一些和它们的各自的优点。 什么是完全新的，样式风格在Java语言和它的运行系统结合它们来产生一个灵通的且强大的编程系统。 在软件中，用Java语言开发的你的应用程序可以在多种机器总体结构、操作系统和图形用户接口之间移植。运用Java语言，诸如软件开发者的工作就会变得简单的多——你会把你的全部精力都集中在最终的目标：准时运送革新的产品、基于可靠的构造的Java语言。较好的开发软件的方法在这里，现在，Java语言平台会带给你这些。 许多动态的语言像Lisp、TCL和 SmallTalk通常被应用于原型构造技术它们成功原因中的一个在于它们非常健壮——你没有必要去担心关于解除或破坏存储器。 同样的，程序员可以相对大胆的处理存储器，当在Java语言里面编程的时候。垃圾回收系统使程序员的工作大为容易，卸下了程序员肩上存储管理之负担，存储分配错误不再发生。
一般认为像Lisp, TCL, 和 SmallTalk这样一些语言十分适合于原型法的另一个理由，是因为它们不要求你受早期决定的约束——这些语言的语义是很丰富的。
Java语言有着严密的对应的属性：它促使你做出清楚的选择。伴随着这些选择带来了许多的协助——你可以写一个方法调用，而且如果你在编写时有一些错误的时候，在编译的时候将会被告知。你没有必要去担心关于方法调用的错误。
英文翻译：
Introduction to Java
autor：Martin Ngobye.
source：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 heterogeneous networks 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 across multiple machine architectures, operating systems, and graphical user interfaces, secure, and high performance, With Java, your job as a software developer is much easier—you focus your full attention
on the end goal of shipping innovative products on time, based on the solid foundation of Java. The better way to develop software is here, now, brought to you by the Java language platform.
Very dynamic languages like Lisp, TCL, and SmallTalk are often used for prototyping. One of the reasons for their success at this is that they are very robust—you don’t have to worry about freeing or corrupting memory.
Similarly, programmers can be relatively fearless about dealing with memory when programming in Java, The garbage collection system makes the programmer’s job vastly easier; with the burden of memory management taken off the programmer’s shoulders, storage allocation errors go away. Another reason commonly given that languages like Lisp, TCL, and SmallTalk are good for prototyping is that they don’t require you to pin down decisions early on—these languages are semantically rich.
Java has exactly the opposite property: it forces you to make explicit choices. Along with these choices come a lot of assistance—you can write method invocations and, if you get something wrong, you get told about it at compile time. You don’t have to worry about method invocation error.
计算机科学与技术1001班 王晓勃
