畢業(yè)論文外文翻譯-J2ME和Java領(lǐng)域

1、原文java 2 micro edition and the world of java1 introductionthe computer revolution of the 1970s increased the demand for sophisticat ed computersoftware to take advantage of the ever-increasing capacity of comp uters to process data.the c programming language became the linchpin that en abled program

2、mers to buildsoftware that was just as robust as the computer it ran on.as the 1980s approached, programmers were witnessing another spurt in t he evolutionof programming language computer technology advanced beyond t he capabilities of the c programming language. the problem wasn't new it oc cu

3、rred previously and caused the demise of generations of programming langua ges. the problem was thatprograms were becoming too complicated to design, write, and manage to keep up with the capabilities of computers it was aroun d this time that a design concept based on simula 67 and smalltalk (from

4、the late 1960s) moved programming to the next evolutionary step. this was the p eriod when object-oriented programming (oop), and with it a new programmin g language called c+, took programmers by storm.in 1979, bjarne stroustmp of bell laboratories in new jersey enhanced t he c programming language

5、 to include object-oriented features. he called the 1 anguage c+. (the + is the incremental operator in the c programming lang uage.) c+ is truly an enhancement of the c programming language, and it be gan as a preprocessor language that was translated into c syntax before the pr ogram was processed

6、 by the compiler.stroustrup built on the concept of a class (taken from simula 67 and smalltal k), from which instances of objects are created a class contains data members and member functions that define an object's data and functionality. he also i ntroduced the concept of inheritance, which

7、enabled a class to inherit some o r all data members and member functions from one or more other classes一all of which complements the concepts of object-oriented programming.by 1988, ansi officials standardized stroustrupt c+ specification.2 enter javajust as c+ was becoming the language of choice f

8、or building industrial-s trength applications, another growth spurt in the evolution of programming lang uage was budding, fertilized by the latest disruptive technology一the world wi de web. the internet had been a well-kept secret for decades before the natio nal science foundation (who oversaw the

9、 internet) removed barriers that preve nted commercialization. until 1991 when it was opened to commerce, the inter net was the almost exclusive domain of government agencies and the academic community. once the barrier to commercialization was lifted, the world wide web一one of several services offe

10、red on the internet一 became a virtual com munity center where visitors could get free information about practically anythi ng and browse through thousands of virtual stores.browsers power the world wide web.a browser translates ascii text file s written in html into an interactive display that can b

11、e interpreted on any machine. as long as the browser is compatible with the correct version of ht ml and http implementation, any computer running the browser can use the same html document without having to modify it for a particular type of c omputer, which was something unheard of at the time. pr

12、ograms written in c or c+ are machine dependent and cannot run on a different machine unless the program is recompiledthe success of the internet gave renewed focus to developing a machine-i ndependent programming language and the same year the internet was comme rcialized, five technologists at sun

13、 microsystems set out to do just that james gosling, patrick naughton, chriswarth, ed frank, and mike sheridan spent 1 8 months developing the programming language they called oak, which was re named java when this new language made its debut in 1995 java went throug h numerous iterations between 19

14、91 and 1995，during which time many other t echnologists at sun made substantial contributions to the language. these inclu ded bill joy, arthur van hoff, jonathan payne, frank yelin, and tim lindhol nralthough java is closely associated with the internet, it was developed as a language for programmi

15、ng software that could be embedded into electronic d evices regardless of the type of cpu used by the device this is known as th e embedded java platform and is in continuous use today for closed systems.the java team from sun succeeded in creating a portable programming la nguage, something that ha

16、d eluded programmers since computers were first pro grammed their success, however, was far beyond their wildest dreams. the sa me concept used to make java programs portable to electronic devices also co uld be used to make java programs run on computers running microsoft wind ows，unix, and macinto

17、sh timing was perfect. the internet/intranet had whet ted corporate americans appetite for cost-effective, portable programs that could replace mission-critical applications within the corporation. and java had prov en itself as a programming language used to successfully develop machine-inde penden

18、t applications.3 java virtual machinewriting java programs is similar to writing c+ programs in that the pro grammer writes source code that contains instructions into an editor, or in an i ntegrated development environment, and then the source code is compiled. however，that's where jav a and c+

19、 part ways. the compiling and linking process of a c+ program results in an executable that can be run on an appropriate machine. in contrast, the java compiler conv erts java source code into bytecode that is executed by the java virtual machine (jv m).machine-specific instmctions are not included

20、in bytecode. instead, they air eady reside in the jvm? which is machine specific. this means that the byteco de might contain fewer instructions that need to be translated than a comparabl e c+ program a lthough the java compiler generates bytecode that must be interpreted by the jvmat mn time, the

21、number of instmctions that need translation are usually minim al and have already been optimized by the java compiler.4 back to the future: j2meremember that java began as a programming language to create programs for embedded systems一microcomputers found in consumer and industrial prod ucts such as

22、 those used to control automobiles and appliances. the developmen t team at sun worked on java in the early 1990s to address the programming needs of the fledgling embedded computer market, but that effort was sidetrack ed by more compelling opportunities presented by the internet.as those opportuni

23、ties were addressed, a new breed of portable communic ations devices opened other opportunities at the turn of the century. cell phone s expanded j2me:thecompletereference from voice communications devices to voice and text communications devices. pocket ele ctronic telephone directories evolved int

24、o personal digital assistants. chipmakers were releasing new products at this time that were designed to transfer comp uting power from a desktop computer into mobile small computers that controll ed gas pumps, cable television boxes, and an assortment of other appliances.the time was right for the

25、next evolution of java however, instead of be efing up java with additional apis，the team at sun, along with the java com munity process program, dismantled both the java programming language and t he java virtual machine. they stripped down java apis and the jvm to the minimum coding required to pr

26、o vide intelligence to embedded systems and microcomputer devices. this was necessa ry because of resource constraints imposed upon the hardware design of these dev ices. the result of their efforts is j2me. j2me is a reduced version of the java api an d java virtual machine that is designed to oper

27、ate within the sparse resources available in the new breed of embedded computers and microcomputers.5 how j2me is organizedtraditional computing devices use fairly standard hardware configurations s uch as a display, keyboard,mouse, and large amounts of memoiy and permanen t storage however，the new

28、breed of computing devices lacks hardware config uration continuity among devices. some devices dortt have a display, permane nt storage, keyboard, or mouse and memory availability is inconsistent among small computing devices. the lack of uniform hardware configuration among t he small computing de

29、vices poses a formidable challenge for the java commu nity process program, which is charged with developing standards for the jvm and the j2me for small computing devices.j2me must service many different kinds of small computing devices, inclu ding screenphones, digital set-top boxes used for cable

30、 television, cell phones, and personal digital assistants. the challenge for the java community process program is to develop a java standard that can be implemented on small comp uting devices that have nonstandard hardware configurations. the java community process program has used a two fold appr

31、oach to addressing the needs of small computing devices. first, they defined the java run-time environment and core classes that operate on each d evice this is referred to as the configuration. a configuration defines the java virtual machine for a particular small computing device. there are two c

32、onfi gurations, one for handheld devices and the other for plug-in devices. next, th e java community process program defined a profile for categories of small c omputing devices a profile consists of classes that enable developers to imple ment features found on a related group of small computing d

33、evices.6 j2me configurationsthere are two configurations for j2me as of this writing. these are conn ected limited device configuration (cldc) and the connected device configu ration (cdc). the cldc is designed for 16-bit or 32-bit small computing dev ices with limited amounts of memory.cldc devices

34、 usually have between 160kb and 512kb of available mem ory and are battery powered. they also use an inconsistent, small-bandwidth ne twork wireless connection and may not have a user interface. cldc devices use the kjava v irtualmachine (kvm) implementation, which is a stripped-down version of the

35、jvm cldcdevices include pagers, personal digital assistants, cell phones, dedicated termin als, andhandheld consumer devices with between 128kjb and 512kb of memory. cdc devices use a 32-bit architecture, have at least two megabytes of memory available, and implement a complete functional jvm cdc de

36、vices include digi tai set-top boxes, home appliances, navigation systems, point-of-sale terminals, and smart phones.7 j2me profilesa profile consists of java classes that enable implementation of features f or either a particular small computing device or for a class of small computing devices. sma

37、ll computing technology continues to evolve, and with that, there is an ongoing process of defining j2me profiles. seven profiles have been de fined as of this writing these are the foundation profile, game profile, mobil e information device profile, pda profile, personal profile, personal basis pr

38、o file, and rmi profile. the foundation profile is used with the cdc configuration and is the core for nearly all other profiles used with the cdc configuration because the foun dation profile contains core java classes the game profile is also used with the cdc configuration and contains the necess

39、aiy classes for developing game applications for any small computing device that uses the cdc configuration. the mobile information device profile (midp) is used with the cldc conf iguration and contains classes that provide local storage, a user interface, and n etworking capabilities to an applica

40、tion that runs on a mobile computing devicesuch as palm os devices. midp is used with wireless java applications. the pdaprofile (pdap) is used with the cldc configuration and contains classes that utilize sophisticated resources found on personal digital assistants these features include better dis

41、plays and larger memory than similar resourcesfound on midp mobile devices (such as cell phones). the personal profile is used with the cdc configuration and the foundation profile and contains classes to implement a complex user interface. the foundation profile provides core classes, and the perso

42、nal profiles provide classes t o implement a sophisticated user interface, which is a user interface that is ca pable of displaying multiple windows at a time. the personal basis profile is similar to the personal profile in that it is use d with the cdc configuration and the foundation profile. how

43、ever, the person al basis profile provides classes to implement a simple user interface, which isa user interface that is capable of displaying one window at a time. the rmi profile is used with the cdc configuration and the foundation pr ofile to provide remote method invocation classes to the core

44、 classes containe d in the foundation profilethere will likely be many profiles as the proliferation of small computing devices ontinues. industiy groups within the java community process program ( boutjava/communityprocess) define profiles. each group establis hes the standard rofile used by small

45、computing devices manufactured by that industry.acdc profile is defined by expanding upon core java classes found in th e foundation rofile with classes specifically targeted to a class of small compu ting device these device-specific classes are contained in a new profile that e nables developers t

46、o create ndustrial-strength applications for those devices. however, if the foundation profile s specific to cdc, not all profiles are expa nded upon the core classes found in the oundation profile, eep in mind that a pplications can access a small computing device software and rdware features only

47、if the necessary classes to do so are contained in the jvm and in the p rofile used by the developer.8 j2me and wireless deviceswith the dramatic increase and sophistication of mobile communications d evices such as cell phones came demand for applications that can run on those devices. consumers an

48、dcorporations want to expand mobile communications devices from voice commu nications to applications traditionally found on laptops and pcs. they want to send and receive email, store and retrieve personal information, perform sophisticated calculations, andplay games.developers, mobile communicati

49、ons device manufacturers, and mobile netw ork p roviders are anxious to fill this need, but there is a serious hurdle: mobile c ommunications devices utilize a number of different application platforms and operating systems.without tweaking the code, an application written for one de vice cannot run

50、 on another devicemobile communications devices lack a standard application platform and o perating system, which has made developing applications for mobile communications de vices a risky economic venture for developers.the lack of standards is nothing new to computing or to any developing t echno

51、log y.traditionally, manufacturers of hardware devices try to corner the market and e nforce their own proprietaiy standard as the de facto standard for the industry usually one upstart succeeds, as in the case of microsoft other times, indust ry leaders form a consortium, such as the java community

52、 process program, t o collectively develop a standard.the wireless application protocol (wap) forum became the initial industr y group that set out to create standards for wireless technology. ericsson, motorola, no kia, andunwired planet formed thewap forum in 1997，and it has since grown to incl ud

53、e nearlyall mobile device manufacturers, mobile network providers, and developers. the wapfomm created mobile communications device standards referred to as thewap standard.the wap standard is an enhancement of html, xml, and tcp/ip. one element of this standard is the wireless markup language speci

54、fication, whic h consists of a blend of html and xml and is used by developers to create documents that can be displayed by a microbrowser. a microbrowser is a di minutive web browser that operates on a mobile communications device.the w ap standard also includes specifications for awireless telepho

55、ny applicationlnt erface (wtai) specification and the wmlscript specification. wtai is used to create an interface for applications that run on a mobile communications devi ce. wmlscript is a stripped-down version of javascript.9 j2me applicationsj2me applications referred to as a midlet can run on

56、practically any mob ile communications device that implements a jvm and midp this encourages de velopers to invest time and money in building applications for mobile communications d evices without the risk that the application is device dependent. however, j2me isrtt seen asa replacement for the wa

57、p specification because both are complementaiy techn ologies.developers whose applications are light-client based continue to use wml and wmlscript. developers turn to j2me for heavier clients that require sophistica ted processing on the mobile communications devicej2me和java領(lǐng)域1.介紹20世紀(jì)70年代以來隨著計算機(jī)革命的

58、開始，對計算機(jī)先進(jìn)軟件的需求人人 增加，從而可以充分利用功能日益增強(qiáng)的精密的計算機(jī)的處理數(shù)據(jù)的能力。c編 程語言逐漸成為支柱，使程序員開發(fā)軟件像計算機(jī)運行一樣流暢。80年代以來，程序員又目睹了編程語言領(lǐng)域的又一次變革的高潮。c語言 的編程能力已經(jīng)不能滿足計算機(jī)的技術(shù)發(fā)展的需要。這問題并不是新問題。它造 成了一代又一代的編程語言的新老更替。問題是，它使得程序設(shè)計過于復(fù)雜，從 而使計算機(jī)軟件的設(shè)計，編寫和開發(fā)落后于硬件的發(fā)展。就是這個吋候，兩種基 于設(shè)計概念的編程語言simula 67和smalltalk （從上世紀(jì)60年代末）帶來了接 近編程語言未來前景的循序漸進(jìn)的步驟。這期間，當(dāng)面向?qū)ο缶幊蹋?/p>

59、oop ）, 與它一種新的編程語言，所謂的c + +在程序員中掀起了一場風(fēng)暴。1979年，bjarne stroustmp的在新澤西州的貝爾實驗室增強(qiáng)了 c語言，使 其具有面向?qū)ο蟮奶攸c即所謂的c + +語言（+ +是c編程語言增強(qiáng)的承載 符號）。c + +是一個真正的提高的c編程語言，它開始是一種前置語言，該 計劃最初是一種編譯工具。stroustrup建立類的概念（借用了 simula 67和sma lltalk中的概念），由類則可以創(chuàng)建實例對象。一個類包含數(shù)據(jù)成員和定義對象 數(shù)據(jù)和功能的成員函數(shù)。他還介紹了繼承的概念，使一類繼承其他一個或多個類 的部分或全部數(shù)據(jù)成員或成員函數(shù)，職能由一個或多個其他類別所有這些概念 就是面向?qū)ο蟮木幊獭?988年由ansi官員將c + +標(biāo)準(zhǔn)化。2走進(jìn)java正當(dāng)c + +作為企業(yè)開發(fā)所選擇的語言吋，由于最新的突破性技術(shù)萬維網(wǎng) 的岀現(xiàn)，