The Java SE 6 Platform Quiz

The following quiz answers cites The Java SE 6
Platform Quiz:

1. What scripting language can you use in the Java SE 6 platform?

Answer (E): The Mozilla
Rhino engine implements the JavaScript technology
scripting language and is available in the core Java Runtime Environment (JRE).
However, the scripting API allows you to use any scripting engine that conforms
with JSR 223.

2. What is the normalization of Unicode text?
Answer (C):
The Java SE 6 platform provides the public java.text.Normalizer
class, which allows you to convert text data to common composed or decomposed
forms, allowing for accurate comparisons and searches on text. Before the Java
SE 6 platform release, the Normalizer class had been hidden in the
Java platform. The class is now a public API.

3. How do you launch your host’s default browser to view a specific
URL?
Answer (B): The Desktop
API allows your program to launch applications associated with certain file
types on the host platform. The current implementation can launch a web browser,
text editor, and email application.

4. How can I sort JTable content?
Answer
(D): A javax.swing.table.TableRowSorter wraps your existing
TableModel. You can configure it to filter or sort your
JTable contents.

5. What is the correct annotation to use to export a method as a web
service operation using Java API for XML Web Services (JAX-WS), version
2.0?
Answer (B): The @WebMethod annotation is used to
mark a method that is exposed as a web service operation. Note that the
@WebService annotation is used to specify that the class is a web
service or that the interface defines a web service. The programmer will likely
use the @WebService annotation in conjunction with the
@WebMethod annotation. See the article “Introducing
JAX-WS 2.0 With the Java SE 6 Platform, Part 1” for more information.

6. In JDK 6, the JMX Monitor API now uses a thread pool to increase
performance. What is the purpose of the JMX Monitor API?
Answer (D):
The JMX
Monitor API allows an application to sample an attribute property of an
MBean periodically and send a notification event if it passes a given threshold.
It now uses a thread pool instead of creating a thread for each monitor. Another
improvement is the ability to monitor a value within a complex type.

7. JDK 6 incorporates an advanced version of the
SwingWorker class into core Java technology. What is the purpose of
the SwingWorker class?
Answer (D): Since the 1998
publication of SwingWorker in the article “Threads
and Swing,” developers have continuously requested that it be moved into
core. At the 2004 JavaOne conference, the Desktop team presented a new version
of SwingWorker that included generification, use of the concurrency
package, and PropertyChangeListener support. Much of this
functionality assists with interthread communication. The Java SE 6 platform
release incorporates a similar version of SwingWorker
that greatly assists developers in processing GUI-driven functionality off the
event-dispatching thread, indicating status and progress and aggregating the
results.

8. What is the best Java platform to use with the upcoming release of
the Microsoft Windows Vista operating system?
Answer (A): The Java
SE 6 platform release works best with the latest user interface (UI)
enhancements of Windows Vista. According to a recent blog entry by Chet Haase: “The
primary delivery of Java for Vista is Java SE 6; that release has received most
of our focus during the Vista beta release timeframe.” Go to the JDK 6 Project site to download the most
recent version. The release is pretty close to final, so it is working very well
at this point. All of the serious Windows Vista problems have been fixed in this
release for months, so it is a particularly good test vehicle for Java
technology on Vista.

9. In the Java SE 6 platform, what key tuning option(s) are needed to
achieve high performance?
Answer (D): See the blog entry “No Tuning
Required: Java SE Out-of-Box Vs. Tuned Performance” for a comparison of
out-of-box and hand-tuned performance.

10. The Java SE 6 platform delivers a technology that can greatly
improve performance by reducing unnecessary synchronization overhead. It allows
a thread to lock and unlock an object with minimal use of atomic operations.
What is this technology called?
Answer (B): The technique called
store-free biased locking eliminates all synchronization-related atomic
operations on uncontended object monitors. The technique supports the bulk
transfer of object ownership from one thread to another, and the selective
disabling of the optimization where unprofitable, using epoch-based bulk
rebiasing and revocation. It has been implemented in the production version of
the Java HotSpot virtual machine (VM) and has yielded significant performance
improvements on a range of benchmarks and applications.

Unicode, UTF等字符编码摘记

两个遵守相同规范的编码标准
unicode 3.0（最新版本5.0）和ISO-10646。从Unicode2.0开始，unicode采用了与ISO 10646-1相同的字库和字码。ISO-10646也叫做UCS (Universal Character Set)。

几个术语：
UTF: Unicode/UCS Transformation Format

UTF-16: 16位编码。基本上是Unicode的双字节编码，额外附加空间用于非常用字符和未来扩充需要（一般很少用到），常用字符在0-0xFFFF，包括扩充空 间的范围是0-0×10FFFF，所以最长编码位数是21位。关于扩充空间，在ISO-10646有相对应的定义。由于它是一个变长码，与CPU字序有关 （例如“汉”字的Unicode编码是6C49。那么写到文件里时，究竟是将6C写在前面，还是将49写在前面？如果将6C写在前面，就是big endian。如果将49写在前面，就是little endian。），最节省空间，所以常作为网络传输的外码。UTF-16是Unicode的preferred encoding。

UTF-8: 由于UTF-16直接就是Unicode编码，没有变换，包含了0×00在编码内，这个在操作系统内（C语言）中有特殊意义（和ASCII不兼容？），会 引起问题，所以有时候需要采用UTF-8编码对Unicode的直接编码做一些变换。UTF-8对ASCII不作变换，进行8位编码，其他字符做变长编 码，每个字符1-3个字节。与CPU字序无关，可以在不同平台之间交流。

UCS-2: 与UTF-16基本一样。

UCS-4: 4字节编码，目前是在UCS-2前加上2个全零的byte。

内码：内码是指操作系统内部的字符编码。早期操作系统的内码是与语言相关的.现在的Windows在内部统一使 用Unicode，然后用代码页适应各种语言,“内码”的概念就比较模糊了。微软一般将缺省代码页指定的编码说成是内码，在特殊的场合也会说自己的内码是 Unicode，例如在GB18030问题的处理上。

字符集：charcterset 字符的集合，例如Unicode是一种字符集。

字符编码：Encoding 如何将二进制数据识别为字符的编码，一种编码表示的字符是有限的，常常一种编码设计为表示一种字符集。例如UTF-8，UTF-16是两种字符编码，它们能够表示Unicode字符集的所有字符。

中国国标编码:

GB 13000: 完全等同于ISO 10646-1/Unicode 2.1, 今后也将随ISO 10646/Unicode的标准更改而同步更改.

GBK: 对GB2312的扩充, 以容纳GB2312字符集范围以外的Unicode 2.1的统一汉字部分, 并且增加了部分unicode中没有的字符.

GB
18030-2000: 基于GB 13000, 作为Unicode 3.0的GBK扩展版本, 覆盖了所有unicode编码,
地位等同于UTF-8, UTF-16, 是一种unicode编码形式. 变长编码, 用单字节/双字节/4字节对字符编码.
GB18030向下兼容GB2312/GBK.
GB 18030是中国所有非手持/嵌入式计算机系统的强制实施标准.

Update (20061114): ISO 8859-1:

ISO/IEC 8859-1，又称Latin-1或“西欧语言”，是国际标准化组织内ISO/IEC 8859的第一个8位字符集。它以ASCII为基础，在空置的0xA0-0xFF的范围内，加入192个字母及符号，借以供使用变音符号的拉丁字母语言使用。

其他：

UCS只是规定如何编码，并没有规定如何传输、保存这个编码。例如“汉”字的UCS编码是6C49，我可
以用4个ascii数字来传输、保存这个编码；也可以用utf-8编码:3个连续的字节E6 B1
89来表示它。关键在于通信双方都要认可。UTF-8、UTF-7、UTF-16都是被广泛接受的方案。UTF-8的一个特别的好处是它与ISO-
8859-1完全兼容。UTF是“UCS Transformation Format”的缩写。

所谓代码页(code page)就是针对一种语言文字的字符编码。例如GBK的code page是CP936，BIG5的code page是CP950，GB2312的code page是CP20936。

　　Windows中有缺省代码页的概念，即缺省用什么编码来解释字符。例如Windows的记事本打开了一个文本文件，里面的内容是字节流：BA、BA、D7、D6。Windows应该去怎么解释它呢？

　
　是按照Unicode编码解释、还是按照GBK解释、还是按照BIG5解释，还是按照ISO8859-1去解释？如果按GBK去解释，就会得到“汉字”
两个字。按照其它编码解释，可能找不到对应的字符，也可能找到错误的字符。所谓“错误”是指与文本作者的本意不符，这时就产生了乱码。

　　答案是Windows按照当前的缺省代码页去解释文本文件里的字节流。缺省代码页可以通过控制面板的区域选项设置。记事本的另存为中有一项ANSI，其实就是按照缺省代码页的编码方法保存。

　　Windows的内码是Unicode，它在技术上可以同时支持多个代码页。只要文件能说明自己使用什么编码，用户又安装了对应的代码页，Windows就能正确显示，例如在HTML文件中就可以指定charset。

趣事：

　　“endian”这个词出自《格列佛游记》。小人国的内战就源于吃鸡蛋时是究竟从大头(Big-Endian)敲开还是从小头(Little-Endian)敲开，由此曾发生过六次叛乱，一个皇帝送了命，另一个丢了王位。

　　我们一般将endian翻译成“字节序”，将big endian和little endian称作“大尾”和“小尾”。

Resources:
1. 对字符编码与Unicode,ISO 10646,UCS,UTF8,UTF16,GBK,GB2312的理解 国际化支持 USENIX.CN - powered by Sinoprise Technology Lab （有比较详细的介绍）

2. 无废话XML

3. 简要解释UCS、UTF、BMP、BOM等名词

4. 中文编码处理(1) －－ 编码与字符集

5. ISO 8859-1

注：文中参考的不全是官方或权威资料，难免有错误，仅作学习用，本人对文中错误不负任何责任，并欢迎改正错误。