java面向特定群体的健康管理平台设计与实现毕业设计英文文献翻译.docx

1、java面向特定群体的健康管理平台设计与实现毕业设计英文文献翻译毕业设计说明书英文文献及中文翻译班 级： 学号： 姓 名： 学 院： 专 业： 指导教师： 2014年 6 月Explore On JAVA, JSP Technology And Three FrameworksDuke, the Java mascot James Gosling, Mike Sheridan, and Patrick Naughton initiated the Java language project in June 1991. Java was originally designed for inter

2、active television, but it was too advanced for the digital cable television industry at the time. The language was initially called Oak after an oak tree that stood outside Goslings office; it went by the name Green later, and was later renamed Java, from a list of random words. Gosling aimed to imp

3、lement a virtual machine and a language that had a familiar C/C+ style of notation.Sun Microsystems released the first public implementation as Java 1.0 in 1995. It promised Write Once, Run Anywhere , providing no-cost run-times on popular platforms. Fairly secure and featuring configurable security

4、, it allowed network- and file-access restrictions. Major web browsers soon incorporated the ability to run Java applets within web pages, and Java quickly became popular. With the advent of Java 2, new versions had multiple configurations built for different types of platforms. For example, J2EE ta

5、rgeted enterprise applications and the greatly stripped-down version J2ME for mobile applications , J2SE designated the Standard Edition. In 2006, for marketing purposes, Sun renamed new J2 versions as Java EE, Java ME, and Java SE, respectively.In 1997, Sun Microsystems approached the ISO/IEC JTC1

6、standards body and later the Ecma International to formalize Java, but it soon withdrew from the process. Java remains a de facto standard, controlled through the Java Community Process. At one time, Sun made most of its Java implementations available without charge, despite their proprietary softwa

7、re status. Sun generated revenue from Java through the selling of licenses for specialized products such as the Java Enterprise System. Sun distinguishes between its Software Development Kit (SDK) and Runtime Environment (JRE) (a subset of the SDK); the primary distinction involves the JREs lack of

8、the compiler, utility programs, and header files. On November 13, 2006, Sun released much of Java as open source software under the terms of the GNU General Public License (GPL). On May 8, 2007, Sun finished the process, making all of Javas core code available under free software/open-source distrib

9、ution terms, aside from a small portion of code to which Sun did not hold the copyright. Suns vice-president Rich Green has said that Suns ideal role with regards to Java is as an evangelist. Following Oracle Corporations acquisition of Sun Microsystems in 20092010, Oracle has described itself as th

10、e steward of Java technology with a relentless commitment to fostering a community of participation and transparency.Principles There were five primary goals in the creation of the Java language:1.It should be simple, object oriented, and familiar2.It should be robust and secure.3.It should be archi

11、tecture neutral and portable4.It should execute with high performance5.It should be interpreted, threaded, and dynamic.Java Platform Main articles: Java (software platform) and Java Virtual Machine One characteristic of Java is portability, which means that computer programs written in the Java lang

12、uage must run similarly on any supported hardware/operating-system platform. This is achieved by compiling the Java language code to an intermediate representation called Java byte code, instead of directly to platform-specific machine code. Java byte code instructions are analogous to machine code,

13、 but are intended to be interpreted by a virtual machine (VM) written specifically for the host hardware. End-users commonly use a Java Runtime Environment (JRE) installed on their own machine for standalone Java applications, or in a Web browser for Java applets. Standardized libraries provide a ge

14、neric way to access host-specific features such as graphics, threading, and networking.A major benefit of using byte code is porting. However, the overhead of interpretation means that interpreted programs almost always run more slowly than programs compiled to native executables would. Just-in-Time

15、 compilers were introduced from an early stage that compile byte codes to machine code during runtime. Implementations Sun Microsystems officially licenses the Java Standard Edition platform for Linux, Mac OS X, and Solaris. Although in the past Sun has licensed Java to Microsoft, the license has ex

16、pired and has not been renewed. Through a network of third-party vendors and licensees, alternative Java environments are available for these and other platforms.Suns trademark license for usage of the Java brand insists that all implementations be compatible. This resulted in a legal dispute with M

17、icrosoft after Sun claimed that the Microsoft implementation did not support RMI or JNI and had added platform-specific features of their own. Sun sued in 1997, and in 2001 won a settlement of US$20 million, as well as a court order enforcing the terms of the license from Sun. As a result, Microsoft

18、 no longer ships Java with Windows, and in recent versions of Windows, Internet Explorer cannot support Java applets without a third-party plugin . Sun, and others, have made available free Java run-time systems for those and other versions of Windows. Platform-independent Java is essential to the J

19、ava EE strategy, and an even more rigorous validation is required to certify an implementation. This environment enables portable server-side applications, such as Web services, Java Servlets, and Enterprise JavaBeans, as well as with embedded systems based on OSGi, using Embedded Java environments.

20、 Through the new GlassFish project, Sun is working to create a fully functional, unified open source implementation of the Java EE technologies. Sun also distributes a superset of the JRE called the Java Development Kit (commonly known as the JDK), which includes development tools such as the Java c

21、ompiler, Java doc, Jar, and debugger.Java performance and garbage collectorsPrograms written in Java have a reputation for being slower and requiring more memory than those written in C. However, Java programs execution speed improved significantly with the introduction of Just-in-time compilation i

22、n 1997/1998 for Java1.1, the addition of language features supporting better code analysis (such as inner classes, String Buffer class, optional assertions, etc.), and optimizations in the Java Virtual Machine itself, such as Hot Spot becoming the default for Suns JVM in 2000. Currently, Java code h

23、as approximately half the performance of C code.Some platforms offer direct hardware support for Java; there are microcontrollers that can run java in hardware instead of a software JVM, and ARM based processors can have hardware support for executing Java byte code through its Jazelle option. Autom

24、atic memory management java uses an automatic garbage collector to manage memory in the object lifecycle. The programmer determines when objects are created, and the Java runtime is responsible for recovering the memory once objects are no longer in use. Once no references to an object remain, the u

25、nreachable memory becomes eligible to be freed automatically by the garbage collector. Something similar to a memory leak may still occur if a programmers code holds a reference to an object that is no longer needed, typically when objects that are no longer needed are stored in containers that are

26、still in use. If methods for a nonexistent object are called, a null pointer exception is thrown.One of the ideas behind Javas automatic memory management model is that programmers can be spared the burden of having to perform manual memory management. In some languages, memory for the creation of o

27、bjects is implicitly allocated on the stack, or explicitly allocated and deal located from the heap. In the latter case the responsibility of managing memory resides with the programmer. If the program does not deal locate an object, a memory leak occurs. If the program attempts to access or deal lo

28、cate memory that has already been deal located, the result is undefined and difficult to predict, and the program is likely to become unstable and/or crash. This can be partially remedied by the use of smart pointers, but these add overhead and complexity. Note that garbage collection does not preve

29、nt logical memory leaks, i.e. those where the memory is still referenced but never used.Garbage collection may happen at any time. Ideally, it will occur when a program is idle. It is guaranteed to be triggered if there is insufficient free memory on the heap to allocate a new object; this can cause

30、 a program to stall momentarily. Explicit memory management is not possible in Java.Java does not support C/C+ style pointer arithmetic, where object addresses and unsigned integers (usually long integers) can be used interchangeably. This allows the garbage collector to relocate referenced objects

31、and ensures type safety and security. As in C+ and some other object-oriented languages, variables of Javas primitive data types are not objects. Values of primitive types are either stored directly in fields (for objects) or on the stack (for methods) rather than on the heap, as commonly true for o

32、bjects (but see Escape analysis). This was a conscious decision by Javas designers for performance reasons. Because of this, Java was not considered to be a pure object-oriented programming language. However, as of Java 5.0, auto boxing enables programmers to proceed as if primitive types were insta

33、nces of their wrapper class. Java contains multiple types of garbage collectors. By default, Hot Spot uses the Concurrent Mark Sweep collector, also known as the CMS Garbage Collector. However, there are also several other garbage collectors that can be used to manage the Heap. For 90% of applications in Ja