java介紹外文翻譯

1、共享知識(shí)分享快樂(lè) 盛年不重來(lái)，一日難再晨。及時(shí)宜自勉，歲月不待人。 外文原文 In troducti on to Java autor： Martin Ngobye. source： Computing Static Slice for Java Programs Java is desig ned to meet the challe nges of applicati on developme nt in the con text of heteroge neous, n etwork-wide distributed en vir onmen ts. Paramou nt among t

2、hese challe nges is secure delivery of applications that consume the minimum of system resources, can run on any hardware and software platform, and can be exte nded dyn amically. Java orig in ated as part of a research project to develop adva need software for a wide variety of n etwork devices and

3、 embedded systems. The goal was to develop a small, reliable, portable, distributed, real-time operating platform. When the project started, C+ was the Ianguage of choice. But over time the difficulties encountered with C+ grew to the point where the problems could best be addressed by creat ing an

4、en tirely new Ian guage platform. Desig n and architecture decisi ons drew from a variety of Ian guages such as Eiffel, SmallTalk, Objective C, and Cedar/Mesa. The result is a Ianguage platform that has proven ideal for develop ing secure, distributed, n etwork based en d-user applicati ons in en vi

5、r onments ranging from n etwork-embedded devices to the World-Wide Web and the desktop. The desig n requireme nts of Java are drive n by the n ature of the comput ing en vir onments in which software must be deployed. The massive growth of the Internet and the World-Wide Web leads us to a completely

6、 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 performanee, and highly robust applications on multiple platforms in heterogeneous, distributed n etworks. Operating on mult

7、iple platforms in heterogeneousnetworks invalidates the traditional schemes of binary distributi on release, upgrade, patch, and so on. To survive in this jun gle, Java must be architecture n eutral, portable, and dyn amically adaptable. The Java system that emerged to meet these needs is simple, so

8、 it can be easily programmed by most developers; familiar, so that curre nt developers can easily lear n Java; object orie nted, to take adva ntage of moder n software developme nt methodologies and to fit into distributed client-server applications; multithreaded, for high performance in applicatio

9、ns that n eed to perform multiple con curre nt activities, such as multimedia; and in terpreted, for maximum portability and dyn amic capabilities. Together, the above requirements comprise quite a collection of buzzwords, so let s exam ine some of them and their respective ben efits before going on

10、. What scompletely new is the manner in which Java and its run-time system have comb ined them to produce a flexible and powerful program ming system. Developing your applications using Java results in software that is portable across multiple mach ine architectures, operat ing systems, and graphica

11、l user in terfaces, secure, and high performanee, With Java, your job as a software developer is much easieyou focus your full attention on the end goal of shipping innovative products on time, based on the solid foun dati on of Java. The better way to develop software is here, now, brought to you b

12、y the Java Ian guage platform. Very dynamic Ianguages 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 htave to worry about freeing or corrupti ng memory. Similarly, programmers can be relatively fearless

13、about dealing with memory when programming in Java, The garbage collection system makes the programmer job vastly easier; with the burden of memory management taken off the programmer shoulders, storage allocati on errors go away. Ano ther reas on common ly give n that la nguages like Lisp, TCL, and

14、 SmallTalk are good for prototyping is that they don tequire you to pin down decisi ons early on these Ian guages are sema ntically rich. Java has exactly the opposite property: it forces you to make explicit choices. Along with these choices come a lot of assistanc you can write method invocations

15、and, if you get something wrong, you get told about it at compile time. You don have to worry about method inv ocati on error. The Java begi nner must grasp 30 basic con cepts Basic con cept 1.In OOP the on ly relati ons is what the object s in terface, such as the computer seller he leaves alone in

16、ternal structure of electrical source, but he is only concerned about that whether the power will be supplied to you, also so long as know can or not but is not how and why.All procedures are make up of certain attribute and the behavior object, the different object visit inv okes through the fun ct

17、i on inv ocati on, betwee n the object all in tercom munion are inv oke through the method inv ocati on, By object data en capsulati on, enhan ces reuse rate very much. 2.ln OOP the most importa nt thought is class, the class is the template ,is a bluepri nt, 卑微如螻蟻、堅(jiān)強(qiáng)似大象 共享知識(shí)分享快樂(lè) con struct an objec

18、t from a class, n amely con struct an in sta nee of the class. 3. En capsulatio n: is that comb ines the data and the behavior in a package) and hides the data the realization process to the object user, in an object data is called its instance field. 4. Through expa nds a class to obta in a new cla

19、ss is called in herita nce, but all classes are con structed by the object super root class of expa nsion, super root class of as follows can make the in troducti on. 5.0bject 3 principal characteristics Behavior- expla ined this object can make what. Tate- whe n the object exerts the method object

20、reflect ion. Dentity- and other similar behavior objects discrimination symbols. Each object has on ly inden tity and among three characteristics they affect mutually. 6. Relati ons among classes: Use-a:Depe ndent relati on Has-a:Polymerization relation Is-a: in heritor relatio n - example:A class h

21、as in herited B class, this time A class not only has B class of method, but also has its own method(Individuality exists in general character) 7.Structure object use structure:Structure proposing, the structure is one special method, the structure object and to its initialization. Example:A Data cl

22、ass of structure calls Data New Data () - structure a new object, also initialize current time. Data happyday=new Data () - an object evaluates an variable happyday, thus en ables this object to be used many times, here be stated the cause variable and the object variable are differe nt. New returns

23、 the value is a quotatio n. Con structor characteristic:The con structor may have 0, one or many parameters The con structor and the class have the same n ame A class may have many con structor. The con structor has not returned value The con structor always be together used with the new operator 8.

24、 Over load ing: When many methods have the same n ame whe n in cludes the different parameter, then has the over loading Which method does the compiler have to choose inv okes. 9. Package : Java allow one or many classes to become together as group, is called package, to orga nizing duty easily, the

25、 sta ndard Java storehouse divides into many packages Java.La ng java.Util java, net and so on, the package is layered and all java packages are in 卑微如螻蟻、堅(jiān)強(qiáng)似大象 共享知識(shí)分享快樂(lè) java and in a javax package. 10. Exte ndable thought: permit to con struct new class on existi ng classes, whe n you extend the cla

26、ss which already existed, then you reuse this class of method and the field, at the same time you might add the new method and the field in the new class. 11. Expandable class:The expandable class fully manifested is-a to extend the relati ons The form is:Class (subclass) exte nds (base class). 12.

27、Multi-modality: In java, the object variable is multi-modality But in java does not support multiple exte nd. 13. D yn amic comb ine: the mecha nism of invoking object method mecha ni sm. 1) compiler exam ines object stateme nt type and method n ame. 2) the compiler exam ines that method inv okes pa

28、rameter type. 3) static combine: If the method type is priavte static the final ,compiler can accurately know which method should inv oke. 4) whe n the procedure runs and uses dyn amic comb ine to inv oke a method, the method editi on which the n hypothesized mach ine must inv oke x the object actua

29、l type which aims at to match. 5) dyn amic comb ine: is a very importa nt characteristic, it can cause the procedure to cha nge aga in may expa nd but does not n eed to tran slate has saved the code. 14. Final class:I n order to preve nt other people derive the new class from yours class, this class

30、 is cannot expa nded. 15. The dyn amic inv ocati on spe nd Ion ger time tha n the static inv ocati on expe nditure. 16. Abstract class:Stipulated or many abstract methods class of itself must defi ne is abstract. Example: Public abstract stri ng getDescripiti on 17.ln Java each class is be exte nded

31、 by object class. 18. equal and toStri ng method in object class . Equal uses in testi ng an object is whether equal with ano ther object. ToStri ng returns to represe nt this object the stri ng of character, each class can n early over loading this method, in order to returns to the current conditi

32、on the correct expression. (The toStri ng method is a very importa nt method) 19. Ge neral program min g:A ny class of type all values all may replace with a object class of variable. 20. The array tabulates: The ArrayList dynamic array tabulates, is a class of storehouse, defi nes in java .In uitl

33、package, but automatic con trol array size. 21.i n class and class of object ,getclass method retur ns to the class type an example, whe n the procedure start contains can in crease in the main method class, hypothesized con fide ntial in crease all classes which he n eeds, each in crease class all

34、must in crease the class which it n eeds. 22. The class: class might dyn amic operate the java code for the compilatio n the procedure to provide the formidable fun ctio n reflect ion, this fun cti on was JavaBea ns is specially useful, the use reflected Java to be able to support the VB programmer

35、to be familiar with the use the tool. procedure of analysis class ability is called the reflector, in Java to provide this function the package to call Java.Lang.The reflect reflection mechanism is extremely formidable. 1) whe n run an alysis class ability. 2) whe n run searches observes a class of

36、object. 3) realizes the gen eral array operati on code. 4) provides the method object. But this mechanism mainly aims at the tool but not the application and the procedure. In the reflection mechanism most important part is that permits class that you in spect structure. With to API in cludes: Java.

37、Lang.Reflect.Field returns to the field. Java.Reflect.Method returns to the method. Java丄ang.Reflect.Constructor returns to the parameter. Method poin ter: Java does not have the method poin ter, makes a method address ano ther method, may invoke it in behi nd, but the in terface is the better solut

38、i on. 23. in terface: should show ing class could do what but not to assig n how to do, a class may realize one or many in terfaces. 24. The in terface is not a class, but is to con forms to a in terface request class of set of sta ndard. If realizes a in terface to n eed 2 steps: 1) the stateme nt

39、class n eeds to realize assig ns the in terface. 2) provides in the in terface all methods defi niti on. Stated a class realizes a in terface to n eed to use the impleme nts key words Class actionB impleme nts Comparable its acti onb n eeds to provide the CompareTo method, the in terface is not the

40、class, cannot use a new example in terface. 25. A class only the n a super class, but a class can realize many in terfaces. In a Java importa nt in terface: Cion eable 26. The in terface and call-back :to programs a com monly used patter n is call-back,i n the pattern, you may refer when this class

41、of pattern settled specific time occurs returns to adjusts on the object the method. Example:Actio nListe ner in terface mon itor. Similar API in cludes: Java.Swi ng.J Optio nPane Java.Swi ng.Timer Java.Awt.Tookit 27.0bject cione:The clone method is a object protection method, this meant your code c

42、annot simple inv oke it. 28.lnner class an inner class definition is the definition in another class. The reas on is: 1) an inner class object can visit founds its object realization, including private data. 2) about other classes in the same package in that, i nner class can be hided. 3) the anonym

43、 ous inner class may the very convenient defi niti on acce nt. In 4) uses the category to be possible the extremely convenient compilati on eve nt driver. 29. Age nt class (proxy): 1) appo inting all codes that in terfaces request 2) all methods (toString equals) that object class define 30. Data ty

44、pe:Java is kind of emphasiz ing type Ian guage, each variable all must be declared its types at first, in java altogether has 8 basic types . four kinds are the long, two kinds are the float, one is the char, being used in the Uni code code char, Boolea n. 1. java is simple Java and C + + are very s

45、imilar, but much simpler. All the high-level program ming Ianguage features, is not absolutely necessaryhave been deleted. For example, Java does not overload operator, the title of the document, pre-processing, computing pointer, the structure of the joint, multi-dimensional array, templates and im

46、plicit type conversion. If you know a little C, C + + or Pascal, you will soon master Java. Here is a simple procedure JavaHelloWorld: publicclassHellol nternet ( publicstaticvoidma in (Stri ngargv )( System. out. println ( Helloln-ternet!) ) ) 2. Java is object-orie nted Java is an object-oriented

47、programming Ianguage. In addition to the simple types, such as digital and Boolean operators in addition, Java is an object of most. As with any object-orie nted Ian guages, Java code also orga ni zed by category. Each category provides a definition of the object behavior. Another type of succession

48、 can be a kind of behavior. In the category of the root level, ofte n the target category. Java support for the sin gle type of inherited hierarchy. This means that each category can only inherit one other category. Some of the Ianguage to allow multiple inheritanee, but it may cause confusion and u

49、nnecessarily complicated Ianguage. For example, imagine that an object would inherit two completely differe nt category. Java also supports the kind of summary of the in terface. This allows programmers to defi ne the in terface methods, and do not have to rush immediately to determ ine the methods

50、to achieve. A type of in terface can be a nu mber of purposes in order to truly multi-inheritance of a number of advantages. The implementation of an object can be any nu mber of in terfaces. IDL in terface and Java in terface very similar. Very easy to set up IDLJ compiler. In other words, Java can

51、 be used to create a CORBA object system distributed object system. In the view of many computer systems use IDL in terface and CORBA objects, such compatibility is importa nt. 3. Java is a type of static In a Java program, it is essential to the definition used by the target (number of characters,

52、suchas an array) type. This will help programmers quickly found because the procedure whe n the compiler can detect the type of error. However, Java System objects are also dynamic types. A requirement for the type of dynamic is often possible, so programmers can write the procedures for differe nt

53、types of objects to do differe nt thi ngs. 4. Is a Java-based compiler When running Java programs, which were first compiled in to byte code. Byte code is very similar to the mach ine in struct ions, so Java program is very efficie nt. However, the byte code does not specifically for a particular ma

54、chine, so no need to recompile Java program can be in many different computer implementation. Java source code files were compiled into a category, which is equivale nt to process byte code performa nce. In a Java class file, and an example for all of the variables are in the light of, and for the f

55、irst time in the impleme ntati on of the code be resolved. This makes the code more com mon and more easily subject to revisi on, but still high. 5. Java is architecture n eutral Java Ian guage is the same for each computer.For example, simple types are the same: 32-bit integer always, always 64-bit

56、 long integers. It is strange, such as C and C + + program ming Ian guage, and so fashi on able it is not the case. As a result of these Ian guages so the definition of freedom, each of the compiler and development environment will be different, so that this process nuisanee become a transplant. Jav

57、a programs can easily gain access to tran spla nts, and there is no n eed to re-compile. 6. Java is a sound Java program can not be caused by the collapse of the computer. Java careful test ing of the system memory of each visit, make sure it is legitimate and will not cause any problems. However, e

58、ven if the Java program may also be wrong. If there is some kind of unexpected things, the process will not collapse, and to abandon the exception. Procedures for such an excepti on would be found to address them. Traditi onal computer programs can access the full memory. May (uncon sciously) to ame

59、 nd any of the value of memory, which will cause problems. Java program can on ly access memory to allow them access to those parts of the Java program can not modify it does not seek to cha nge the value. 7. Java is a compact As the Java is desig ned to run on a small computer, as a program ming Ia

60、n guage for the system is relatively small. It effectively in more than 4MB of RAM to run on PC machine. Java tran slator occupied by on ly a few hun dred KB. This tran slator for the Java platform independence and portability is reliable. Due to Java is very small, it is a very small computer memor