【正文】 again,39。 a nonobjectoriented carpenter would think primarily of his tools. The objectoriented facilities of Java are essentially those of C++. Object orientation has proven its worth in the last 30 years, and it is inconceivable that a modern programming language would not use it. Indeed, the objectoriented features of Java are parable to those of C++. The major difference between Java and C++ lies in multiple inheritance, which Java has replaced with the simpler concept of interfaces, and in the Java metaclass model. The reflection mechanism and object serialization feature make it much easier to implement persistent objects and GUI builders that can integrate offtheshelf ponents. 3. Distributed Java has an extensive library of routines for coping with TCP/IP protocols like HTTP and FTP. Java applications can open and access objects across the Net via URLs with the same ease as when accessing a local file system. We have found the working capabilities of Java to be both strong and easy to use. Anyone who has tried to do Inter programming using another language will revel in how simple Java makes onerous tasks like opening a socket connection. (We cover working in Volume 2 of this book.) The remote method invocation mechanism enables munication between distributed objects (also covered in Volume 2).There is now a separate architecture, the Java 2 Enterprise Edition (J2EE), that supports very large scale distributed applications. 4. Robust Java is intended for writing programs that must be reliable in a variety of ways. Java puts a lot of emphasis on early checking for possible problems, later dynamic (runtime) checking, and eliminating situations that are errorprone.? The single biggest difference between Java and C/C++ is that Java has a pointer model that eliminates the possibility of overwriting memory and corrupting data. This feature is also very useful. The Java piler detects many problems that, in other languages, would show up only at run time. As for the second point, anyone who has spent hours chasing memory corruption caused by a pointer bug will be very happy with this feature of Java. If you are ing from a language like Visual Basic that doesn39。s standard practice. So even though we found that C++ was unsuitable, we designed Java as closely to C++ as possible in order to make the system more prehensible. Java omits many rarely used, poorly understood, confusing features of C++ that, in our experience, bring more grief than benefit. The syntax for Java is, indeed, a cleanedup version of the syntax for C++. There is no need for header files, pointer arithmetic (or even a pointer syntax), structures, unions, operator overloading, virtual base classes, and so on. (See the C++ notes interspersed throughout the text for more on the differences between Java and C++.) The designers did not, however, attempt to fix all of the clumsy features of C++. For example, the syntax of the switch statement is unchanged in Java. If you know C++, you will find the transition to the Java syntax easy. If you are used to a visual programming environment (such as Visual Basic), you will not find Java simple. There is much strange syntax (though it does not take long to get the hang of it). More important, you must do a lot more programming in Java. The beauty of Visual Basic is that its visual design environment almost automatically provides a lot of the infrastructure for an application. The equivalent functionality must be programmed manually, usually with a fair bit of code, in Java. There are, however, thirdparty development environments that provide draganddropstyle program development. Another aspect of being simple is being small. One of the goals of Java is to enable the construction of software that can run standalone in small machines. The size of the basic interpreter and class support is about 40K bytes。 附件 2：外文原文 （復(fù)印件） Java Technical Description Java as a Programming Platform Java is certainly a good programming language. There is no doubt that it is one of the better languages available to serious programmers. We think it could potentially have been a great programming language, but it is probably too late for that. Once a language is out in the field, the ugly reality of patibility with existing code sets in. Java was never just a language. There are lots of programming languages out there, and few of them make much of a splash. Java is a whole platform, with a huge library, containing lots of reusable code, and an execution environment that provides services such as security, portability across operating systems, and automatic garbage collection. As a programmer, you will want a language with a pleasant syntax and prehensible semantics (., not C++). Java fits the bill, as do dozens of other fine languages. Some languages give you portability, garbage collection, and the like, but they don39。我們必須承認(rèn)還沒(méi)有看到一個(gè)運(yùn)行在手機(jī)上的 Java 應(yīng)用程序是必不可少的。即便如此，這種好事也沒(méi)有發(fā) 生。家庭用戶將會(huì)放棄功能強(qiáng)大且便利的桌面系統(tǒng)，而使用沒(méi)有本地存儲(chǔ)的網(wǎng)絡(luò)設(shè)備是一種荒謬的想法。 12)使用 Java 可以用價(jià)值 500 美元的 Inter 設(shè)備取代電腦。 JavaScript 是一種在網(wǎng)頁(yè)中使用的腳本語(yǔ)言，它是由 Netscape 發(fā)明的，原來(lái)的名字叫做 LiveScripto JavaScript 的語(yǔ)法類似 Java，除此之外，兩者無(wú)任何關(guān)系 (當(dāng)然，名字有些相像 )。而打開 Word文檔遭到襲擊的風(fēng)險(xiǎn)則相當(dāng)于步行橫穿繁忙的高速公路而遇難的風(fēng)險(xiǎn)。 有些系統(tǒng)管理員在公司的瀏覽器中禁用 Java，卻允許其用戶下載可執(zhí)行文件、ActiveX 控件和 Word 文檔。想想看 :毫不夸張地說(shuō)，有數(shù)百萬(wàn)種病毒攻擊著 Windows 的可執(zhí)行文件和 Word 宏，這給系統(tǒng)造成了巨大的損害，但卻很少有人批評(píng)被攻擊平臺(tái)的脆弱。隨后，人們很快就解決了引發(fā)問(wèn)題的所有技術(shù)因素。大多數(shù)安全問(wèn)題都存在于 Java 的特定瀏覽器中。 10) Java 程序是主要的安全風(fēng)險(xiǎn)。在使用 JDBC 這類的數(shù)據(jù)庫(kù)存取工具時(shí)， Java 語(yǔ)言就更是責(zé)無(wú)旁貸了。把代碼移到另一臺(tái)機(jī)器上直接運(yùn)行就行了。同時(shí)，也完全可以編寫一個(gè)獨(dú)立的、不依賴于Web瀏覽器運(yùn)行的 Java 程序，并且十分有用。 所有的 Java applet 都是在網(wǎng)頁(yè)瀏覽器中運(yùn)行的。就這一點(diǎn)來(lái)說(shuō)，那些抱怨聽起來(lái)像狐貍抱怨葡萄酸，并且一些誹謗者已經(jīng)轉(zhuǎn)過(guò)來(lái)攻擊 Java 用戶界面不漂亮而不是攻擊速度慢了。但是，今天的計(jì)算機(jī)比人們發(fā)出抱怨的時(shí)候已經(jīng)快了很多很多。另外， Java GUI 要比本地的 GUI 慢一些，因?yàn)樗鼈儾捎门c平臺(tái)無(wú)關(guān)的方式繪制圖形。垃圾回收會(huì)比手工內(nèi)存管理稍微慢一些，并且實(shí)現(xiàn)同樣的功能， Java 程序需要的內(nèi)存量要比 C++程序大?，F(xiàn)在除了像手機(jī)這樣的“微型”平臺(tái)之外， Java 虛擬機(jī)使用了即時(shí)編譯器，因此采用 Java 編寫的“熱