2011年3月7日
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摘要: 一個完整的自動化測試框架體系包含以下幾個部分：1、自動化測試框架；2、測試腳本以及測試數(shù)據(jù)管理；3、測試腳本的執(zhí)行管理系統(tǒng)；4、測試結果的顯示與分析系統(tǒng)。其中最重要的是自動化測試框架部分。
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摘要: JUnit
JUnit是由 Erich Gamma 和 Kent Beck 編寫的一個回歸測試框架（regression testing framework）。Junit測試是程序員測試，即所謂白盒測試，因為程序員知道被測試的軟件如何（How）完成功能和完成什么樣（What）的功能。Junit是一套框架，繼承TestCase類，就可以用Junit進行自動測試了。
更多JUnit信息
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摘要: Have you wondered why certain programs are located under /bin, or /sbin, or /usr/bin, or /usr/sbin?
For example, less command is located under /usr/bin directory. Why not /bin, or /sbin, or /usr/sbin? What is the different between all these directories?
In this article, let us review the Linux filesystem structures and understand the meaning of individual high-level directories
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摘要: 當今互聯(lián)網(wǎng)的發(fā)展，已不是大魚吃小魚的時代，而是快魚吃慢魚的時代。互聯(lián)網(wǎng)產品的制勝原則就是一個字——“快”。在各種形態(tài)的產品研發(fā)中，我們始終貫徹如一的價值觀之一就是“快”，我們應該如何來理解和詮釋“快”？又會從哪些方面來執(zhí)行貫徹這個原則呢？
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摘要: 軟件測試的十二個誤區(qū)大體總結如下：
1) 測試人員不需要了解軟件開發(fā)的知識：
這個很要命的，我們談到軟件測試人員未來的發(fā)展方向大致有：自動化測試，性能測試，測試管理，項目經(jīng)理。這其中自動化測試和性能測試包括項目管理，都會要求對軟件開發(fā)有深入的理解，如何能設計一個好的自動化框架，好的性能測試用例，如何管理一個開發(fā)團隊，這都需要我們在軟件開發(fā)方面有所掌握。不單要掌握，而且要精通。此其一。
其二：如果不了解開發(fā)知識，測試人員很容易被開發(fā)人員牽著鼻子走，因為開發(fā)人員隨便一忽悠，你如果不了解個中奧妙，你一個字也說不上來。(以前我們討論 Cookie和Session，由于GoAhead不支持Session，只能用Cookie來控制，差點別開發(fā)人員忽悠了)
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摘要: 寫在前面：寫Android程序有一個很重要的原則，不阻塞UI線程。因此Android提供了5種方法來，讓一些耗時的作業(yè)在其它線程中執(zhí)行，然后把結果返回給UI線程，以免阻塞UI線程。
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探討了軟件測試的可測試性，主要包括Controllability, Observability, Availability,Simplicity, Stability 和 Information.
HeuristicsOfSoftwareTestability.pdf
摘要: android的selector的用法：
首先android的selector是在drawable/xxx.xml中配置的。
先看一下listview中的狀態(tài)：
把下面的XML文件保存成你自己命名的.xml文件（比如list_item_bg.xml），在系統(tǒng)使用時根據(jù)ListView中的列表項的狀態(tài)來使用相應的背景圖片。drawable/list_item_bg.xml
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摘要: The Monkey is a command-line tool that that you can run on any emulator instance or on a device. It sends a pseudo-random stream of user events into the system, which acts as a stress test on the application software you are developing.
The Monkey includes a number of options, but they break down into four primary categories:
Basic configuration options, such as setting the number of events to attempt.
Operational constraints, such as restricting the test to a single packag
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摘要: Programmers can configure logging either by creating loggers, handlers, and formatters explicitly in a main module with the configuration methods listed above (using Python code), or by creating a logging config file. The following code is an example of configuring a very simple logger, a console handler, and a simple formatter in a Python module:
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摘要: Android系統(tǒng)中Looper負責管理線程的消息隊列和消息循環(huán)，具體實現(xiàn)請參考Looper的源碼。 可以通過Loop.myLooper()得到當前線程的Looper對象，通過Loop.getMainLooper()可以獲得當前進程的主線程的Looper對象。
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摘要: The list below defines some of the basic terminology of the Android platform.
.apk file
Android application package file. Each Android application is compiled and packaged in a single file that includes all of the application's code (.dex files), resources, assets, and manifest file. The application package file can have any name but must use the .apk extension. For example: myExampleAppname.apk. For convenience, an application package file is often referred to as an ".apk".
Re
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摘要: C.__init__(self[, arg1, ...] )
Constructor (with any optional arguments)
C.__new__(self[, arg1, ...] )[a]
Constructor (with any optional argu ments); usually used for setting up subclassing of immutable data types
C.__del__(self)
Destructor
C.__str__(self)
Printable string representation; str() built-in and print statement
C.__repr__(self)
Evaluatable string representation; repr() built-in and '' operator
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摘要: 本來這是個老生常談的問題，上周自成又分享了一些性能優(yōu)化的建議，我這里再做一個全面的Tips整理，謹作為查閱型的文檔，不妥之處，還請指正；
如果你已經(jīng)對yahoo這些優(yōu)化建議爛熟于心，果斷點這里
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Five test auomation framework are discussed in this paper.
1) The Test Script Modularity Framework
2) The Test Library Architecture Framework
3) The Keyword-Driven or Table-Driven Testing Framework
4) The Data-Driven Testing Framework
5) The Hybrid Test Automation
摘要: 一、ASE(Android Scripting Environment)為Android系統(tǒng)帶來了腳本語言的技術，通過它我們可以編輯和執(zhí)行腳本，和腳本解釋交互。腳本可以訪問多數(shù)Android API,目前有一個開源項目叫做Scripting Layer for Android (SL4A) ，提供了對python,javaScript, Lua等腳本的支持。ASE主要通過兩種方式來訪問 Android API,一種是通過JSON-RPC來訪問,另外一種通過BeanShell（Java語言的動態(tài)版本）直接訪問Android API。SL4AL架構如下圖：
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摘要: 2.你需要學習JAVA語言的基礎知識以及它的核心類庫 (collections，serialization，streams，networking， multithreading，reflection，event，handling，NIO，localization，以及其他)。
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1)
http://www.pythonchallenge.com/ 提供了不同level的Python題目，非常有趣的題目。做完一題后，把URL中的pc改為pcc可以看到上一題的答案
2)
http://projecteuler.net/ 里面有200多道題目，不要要求提交代碼，只要最終答案，提供用各種語言來解決問題。這里（
http://dcy.is-programmer.com/posts/8750.html）有部分題目的答案
非常好玩，有興趣的朋友，快來試試吧
看看 project euler 的第一道題：
If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23. Find the sum of all the multiples of 3 or 5 below 1000.
用 python 語言寫出來是：
print sum(i for i in xrange(1, 1000) if i % 3 == 0 or i % 5 == 0)
This is the first edition of what is expected to become a recurring series on InfoQ. The idea behind this minibook is that a number of InfoQ articles and interviews which deal with a particular topic (in this case, REpresentational State Transfer, or REST) are combined together to provide a detailed exploration suitable for both beginners and advanced practitioners.
Read More: http://www.infoq.com/minibooks/emag-03-2010-rest;jsessionid=1E2375E822D980824403DAD46588FAFE
摘要: #Trie Tree的基本特點
1）根節(jié)點不包含字符，除根節(jié)點外每個節(jié)點只包含一個字符
2）從根節(jié)點到某一個節(jié)點，路徑上經(jīng)過的字符連接起來，為該節(jié)點對應的字符串
3）每個節(jié)點的所有子節(jié)點包含的字符串不相同
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摘要: The Bloom filter, conceived by Burton Howard Bloom in 1970, is a space-efficient probabilistic data structure that is used to test whether an element is a member of a set.False positivesare possible, but false negatives are not. Elements can be added to the set, but not removed (though this can be addressed with a counting filter). The more elements that are added to the set, the larger the probability of false positives
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摘要: These posts have garnered a number of interesting comments. I want to address two of the negative ones in this post. Both are of the same general opinion that I am abandoning testers and that Google is not a nice place to ply this trade. I am puzzled by these comments because nothing could be further from the truth. One such negative comment I can take as a one-off but two smart people (hey they are reading this blog, right?) having this impression requires a rebuttal. Here are the comments:
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摘要: One of the key ways Google achieves good results with fewer testers than many companies is that we rarely attempt to ship a large set of features at once. In fact, the exact opposite is often the goal: build the core of a product and release it the moment it is useful to as large a crowd as feasible, then get their feedback and iterate. This is what we did with Gmail, a product that kept its beta tag for four years. That tag was our warning to users that it was still being perfected. We removed
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摘要: Lots of questions in the comments to the last two posts. I am not ignoring them. Hopefully many of them will be answered here and in following posts. I am just getting started on this topic.
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摘要: Android applications are, at least on the T-Mobile G1, limited to 16 MB of heap. It's both a lot of memory for a phone and yet very little for what some developers want to achieve. Even if you do not plan on using all of this memory, you should use as little as possible to let other applications run without getting them killed. The more applications Android can keep in memory, the faster it will be for the user to switch between his apps. As part of my job, I ran into memory leaks issues in Andr
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摘要: The Java community is now swamped with discussions about Oracle's patent suit against Google's Android platform. I've been contributing my opinion in several places, but there is one critical topic that needs repeating the same comments everywhere... so, this blog spills the beans once and completely.
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摘要: Activities in the system are managed as an activity stack. When a new activity is started, it is placed on the top of the stack and becomes the running activity -- the previous activity always remains below it in the stack, and will not come to the foreground again until the new activity exits.
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摘要: The one question I get more than any other is "How does Google test?" It's been explained in bits and pieces on this blog but the explanation is due an update
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摘要: Dependency injection asks us to separate the new operators from the application logic. This separation forces your code to have factories which are responsible for wiring your application together. However, better than writing factories, we want to use automatic dependency injection such as GUICE to do the wiring for us. But can DI really save us from all of the new operators?
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摘要: Everyone seems to think that they are writing OO after all they are using OO languages such as Java, Python or Ruby. But if you exam the code it is often procedural in nature
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By James Whittaker
I’ve had a number of questions about the SET role and it seems I have confused folks when I say that the SWE is a tester and the SET is a tester and at the same time the SWE is a developer and the SET is a developer. What could possibly be confusing about that?
Oh, yeah. Right.
My next series of posts are going to detail the role of the SET and all will eventually be clear but some clarification on career path seems worthwhile.
SETs are developers who write test code and automation as their primary task. They are in every sense of the word a developer. When we interview SETs, SWEs are on the interview loop and SWE questions are asked. They are not all of the interview, but they are part of it.
This means that the skill set that our SETs possess makes them perfect candidates for switching to the SWE role. There is neither incentive nor deterrent to do so. SETs and SWEs are on the same pay scale and bonus structure (I have both roles reporting to me so I have real visibility into salary data) and their promotion velocity (again based on actual data) is roughly equivalent. This means that SETs have no outside influences to prompt them one way or the other.
The key factor is really the type of work you are doing. SETs who find themselves involved in SWE work usually convert to SWE. SWEs are also drawn in the opposite direction. Much of this happens through our 20% time work. Any SET interested in SWE work can take on a 20% task doing feature development. Any SWE interested in automation can find a group and sign up for a 20%. Right now I have both SWEs and SETs involved in such cross pollination.
The ideal situation is that the title reflects the actual work that you are involved in. So if an SET starts doing more feature dev work than automation, he or she should convert, same for SWEs doing automation work. In my time here, conversions in both directions have happened, but it is not all that common. The work of both roles is engaging, interesting and intense. Few Googlers are walking around bored.
Bottom line: do the work you are passionate about and capable of and the right job title will find you.
一、概念
靜態(tài)分派（Static Dispatch），發(fā)生在編譯時期，分派是根據(jù)靜態(tài)類型信息發(fā)生的，方法重載就是靜態(tài)分派。
動態(tài)分派（Dynamic Dispatch），發(fā)生在運行時期，動態(tài)分派動態(tài)地置換掉某個方法。面向對象的語言用動態(tài)分派實現(xiàn)多態(tài)性。
Java語言支持靜態(tài)多分派和動態(tài)的單分派，利用設計模式Java可以實現(xiàn)Double Dispatch，即訪問者模式。
二、Visitor Pattern
目的：封裝一些施加于某種數(shù)據(jù)結構元素之上的操作。
UML圖：
主要原理：“反傳球”，Element來Visitor之間二輪調用，調用過程中用sinlge dispatch確定類型
記錄關于REST的一些技術：
1、REST簡介：http://zh.wikipedia.org/zh/REST
2、InfoQ 深入淺出REST: http://www.infoq.com/cn/articles/rest-introduction
摘要: 要設計良好的架構，必須做到關注點分離，這樣可以產生高內聚、低耦合的系統(tǒng)，這是美麗架構的終極原則
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摘要: A synchronization aid that allows a set of threads to all wait for each other to reach a common barrier point. CyclicBarriers are useful in programs involving a fixed sized party of threads that must occasionally wait for each other. The barrier is called cyclic because it can be re-used after the waiting threads are released.
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摘要: A java.util.concurrent.CountDownLatch is a concurrency construct that allows one or more threads to wait for a given set of operations to complete
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文章描述了實現(xiàn) Multithreaded Servers的3種方法：
1）單線程，性能性差，請求等待時間長
2）多線程，把接受請求和處理請求的線程分開，接受后交給 worker處理
3）線程池，性能最佳，有效地防止負載過重，重復利用線程，請求多時，讓請求排隊接收處理
4）主要用socket來通信， ServerSocket 和 Socket
具體文章請看：http://tutorials.jenkov.com/java-multithreaded-servers/index.html
摘要: 軟件模塊之間總是存在著一定的接口，從調用方式上，可以把他們分為三類：同步調用、回調和異步調用。
同步調用是一種阻塞式調用，調用方要等待對方執(zhí)行完畢才返回，它是一種單向調用，如HTTP；
回調是一種雙向調用模式，也就是說，被調用方在接口被調用時也會調用對方的接口；
異步調用是一種類似消息或事件的機制，不過它的調用方向剛好相反，接口的服務在收到某種訊息或發(fā)生某種事件時，會主動通知客戶方（即調用客戶方的接口），如JMS；
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摘要: 雖然很少有 Java? 開發(fā)人員能夠忽視多線程編程和支持它的 Java 平臺庫，更少有人有時間深入研究線程。相反地，我們臨時學習線程，在需要時向我們的工具箱添加新的技巧和技術。以這種方式構建和運行適當?shù)膽贸绦蚴强尚械模悄梢宰龅牟恢惯@些。理解 Java 編譯器的線程處理特性和 JVM 將有助于您編寫更高效、性能更好的 Java 代碼
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The Zen of Python, by Tim Peters
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!
摘要: This is the text of the Commencement address by Steve Jobs, CEO of Apple Computer and of Pixar Animation Studios, delivered on June 12, 2005.
I am honored to be with you today at your commencement from one of the finest universities in the world. I never graduated from college. Truth be told, this is the closest I’ve ever gotten to a college graduation. Today I want to tell you three stories from my life. That’s it. No big deal. Just three stories.
The first story is about conn
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摘要: 1. 軟件架構概述
1.1 什么是軟件架構
◎ 軟件架構的概念很混亂。如果你問五個不同的人，可能會得到五種不同的答案。
◎ 軟件架構概念主要分為兩大流派：
組成派：軟件架構 = 組件 + 交互。
決策派：軟件架構 = 重要決策集。
◎ 組成派和決策派的概念相輔相成。
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摘要: 所謂第一范式（1NF）是指數(shù)據(jù)庫表的每一列都是不可分割的基本數(shù)據(jù)項，同一列中不能有多個值，即實體中的某個屬性不能有多個值或者不能有重復的屬性。如果出現(xiàn)重復的屬性，就可能需要定義一個新的實體，新的實體由重復的屬性構成，新實體與原實體之間為一對多關系。在第一范式（1NF）中表的每一行只包含一個實例的信息。簡而言之，第一范式就是無重復的列。
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OS實時監(jiān)控工具dstat，整合了vmstat, iostat, ifstat, netstat等常見os監(jiān)控工具的優(yōu)點，輸出的結果簡單直觀，并且結果可以保存到csv文件。
dokie@ubuntu:~$ dstat
----total-cpu-usage---- -dsk/total- -net/total- ---paging-- ---system--
usr sys idl wai hiq siq| read writ| recv send| in out | int csw
14 5 78 3 0 0| 553k 109k| 0 0 | 83B 989B| 983 2190
8 2 90 0 0 0| 0 0 |2076B 1383B| 0 0 |1076 1407
9 3 89 0 0 0| 0 72k|7530B 420B| 0 0 | 721 1501
9 4 87 0 0 0| 0 0 |9547B 564B| 0 0 | 750 1474
8 2 89 0 0 0| 0 0 | 12k 672B| 0 0 | 772 1681
9 2 89 0 0 0| 0 0 | 13k 792B| 0 0 | 677 1396
dokie@ubuntu:~$ dstat -h
Usage: dstat [-afv] [options..] [delay [count]]
Versatile tool for generating system resource statistics
Dstat options:
-c, --cpu enable cpu stats
-C 0,3,total include cpu0, cpu3 and total
-d, --disk enable disk stats
-D total,hda include hda and total
-g, --page enable page stats
-i, --int enable interrupt stats
-I 5,eth2 include int5 and interrupt used by eth2
-l, --load enable load stats
-m, --mem enable memory stats
-n, --net enable network stats
-N eth1,total include eth1 and total
-p, --proc enable process stats
-r, --io enable io stats (I/O requests completed)
-s, --swap enable swap stats
-S swap1,total include swap1 and total
-t, --time enable time/date output
-T, --epoch enable time counter (seconds since epoch)
-y, --sys enable system stats
--aio enable aio stats
--fs enable fs stats
--ipc enable ipc stats
--lock enable lock stats
--raw enable raw stats
--socket enable socket stats
--tcp enable tcp stats
--udp enable udp stats
--unix enable unix stats
--vm enable vm stats
-M stat1,stat2 enable external plugins
--mods stat1,stat2
--list list all internal and external plugins
-a, --all equals -cdngy (default)
-f, --full expand -C, -D, -I, -N and -S discovery lists
-v, --vmstat equals -pmgdsc -D total
--integer show integer values
--nocolor disable colors (implies --noupdate)
--noheaders disable repetitive headers
--noupdate disable intermediate updates
--output file write CSV output to file
delay is the delay in seconds between each update
count is the number of updates to display before exiting
The default delay is 1 and count is unspecified (unlimited)
常用的命令：dstat -cdlmnpsy
導出為CVS:
dstat -ta --output osstat.csv
1. 安裝JDK
http://wiki.ubuntu.org.cn/Java%E5%AE%89%E8%A3%85%E9%85%8D%E7%BD%AE
2. 安裝Python
1). apt-get install python
2). PyDev for eclipse:
Name：PyDev，Location：http://pydev.org/updates
Ref:http://www.cnblogs.com/Realh/archive/2010/10/10/1847251.html
3. 安裝dstat--性能監(jiān)測工具
apt-get install dstat
下面是來自 Taobao QA Team中的安全測試方面的文章，對初學者很有指導意義
安全測試學習筆記系列：
1. http://qa.taobao.com/?p=11352
2.http://qa.taobao.com/?p=11363
3.http://qa.taobao.com/?p=11472
4.http://qa.taobao.com/?p=11479
5.http://qa.taobao.com/?p=11484
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WEB漏洞攻擊之SQL注入:http://qa.taobao.com/?p=11403
摘要: onabort 當用戶中斷下載圖像時觸發(fā)。
onactivate 當對象設置為活動元素時觸發(fā)。
onafterprint 對象所關聯(lián)的文檔打印或打印預覽后立即在對象上觸發(fā)。
onafterupdate 當成功更新數(shù)據(jù)源對象中的關聯(lián)對象后在數(shù)據(jù)綁定對象上觸發(fā)。
onbeforeactivate new 對象要被設置為當前元素前立即觸發(fā)。
onbeforecopy 當選中區(qū)復制到系統(tǒng)剪貼板之前在源對象觸發(fā)。
onbeforecut 當選中區(qū)從文檔中刪除之前在源對象觸發(fā)。
onbeforedeactivate 在 activeElement 從當前對象變?yōu)楦肝臋n其它對象之前立即觸發(fā)。
onbeforeeditfocus 在包含于可編輯元素內的對象進入用戶界面激活狀態(tài)前或可編輯容器變成控件選中區(qū)前觸發(fā)。
onbeforepaste 在選中區(qū)從系統(tǒng)剪貼板粘貼到文檔前在目標對象上觸發(fā)。
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數(shù)組類Array是Java中最基本的一個存儲結構。它用于存儲一組連續(xù)的對象或基本類型的數(shù)據(jù)。其中的元素的類型必須相同。
Array是最有效率的一 種：
1、效率高，但容量固定且無法動態(tài)改變。 Array還有一個缺點是，無法判斷其中實際存有多少元素，length只是告訴我們Array的容量。
2、Java中有一個Arrays類，專門用來操作Array，提供搜索、排序、復制等靜態(tài)方法。 equals()：比較兩個Array是否相等，Array擁有相同元素個數(shù)，且所有對應元素兩兩相等。 fill()：將值填入Array中。 sort()：用來對Array進行排序。 binarySearch()：在排好序的Array中尋找元素。 System.arraycopy()：Array的復制。
Java Collections Framework成員主要包括兩種類型，即：Collection和Map類型。 在Java中提供了Collection和Map接口。其中List和Set繼承了Collection接口；Vector、ArrayList、 LinkedList三個類實現(xiàn)List接口，HashSet、TreeSet實現(xiàn)Set接口，HashTable、HashMap、 TreeMap實現(xiàn)Map接口。由此可見，Java中用8種類型的基本數(shù)據(jù)結構來實現(xiàn)其Collections Framework；下面分別進行介紹。
Vector：基于Array的List，性能也就不可能超越Array，并且Vector是"sychronized"的，這個也是Vector和ArrayList的唯一的區(qū)別。
ArrayList：同Vector一樣是一個基于Array的，但是不同的是ArrayList不是同步的。所以在性能上要比Vector優(yōu)越一些，但 是當運行到多線程環(huán)境中時，可需要自己在管理線程的同步問題。從其命名中可以看出它是一種類似數(shù)組的形式進行存儲，因此它的隨機訪問速度極快。
LinkedList：LinkedList不同于前面兩種List，它不是基于Array的，所以不受Array性能的限制。它每一個節(jié)點（Node） 都包含兩方面的內容：
1、節(jié)點本身的數(shù)據(jù)（data）；
2、下一個節(jié)點的信息（nextNode）。所以當對LinkedList做添加，刪除動作的時候 就不用像基于Array的List一樣，必須進行大量的數(shù)據(jù)移動。只要更改nextNode的相關信息就可以實現(xiàn)了所以它適合于進行頻繁進行插入和刪除操 作。這就是LinkedList的優(yōu)勢。Iterator只能對容器進行向前遍歷，而 ListIterator則繼承了Iterator的思想，并提供了對List進行雙向遍歷的方法。
List總結：
1、所有的List中只能容納單個不同類型的對象組成的表，而不是Key－Value鍵值對。例如：[ tom,1,c ]；
2、所有的List中可以有相同的元素，例如Vector中可以有 [ tom,koo,too,koo ]；
3、所有的List中可以有null元素，例如[ tom,null,1 ]；
4、基于Array的List（Vector，ArrayList）適合查詢，而LinkedList（鏈表）適合添加，刪除操作。
HashSet：雖然Set同List都實現(xiàn)了Collection接口，但是他們的實現(xiàn)方式卻大不一樣。List基本上都是以Array為基礎。但是 Set則是在HashMap的基礎上來實現(xiàn)的，這個就是Set和List的根本區(qū)別。HashSet的存儲方式是把HashMap中的Key作為Set的 對應存儲項，這也是為什么在Set中不能像在List中一樣有重復的項的根本原因，因為HashMap的key是不能有重復的。HashSet能快速定位 一個元素，但是放到HashSet中的對象需要實現(xiàn)hashCode()方法0。
TreeSet則將放入其中的元素按序存放，這就要求你放入其中的對象是可排序的，這就用到了集合框架提供的另外兩個實用類Comparable和 Comparator。一個類是可排序的，它就應該實現(xiàn)Comparable接口。有時多個類具有相同的排序算法，那就不需要重復定義相同的排序算法，只要實現(xiàn)Comparator接口即可。TreeSet是SortedSet的子類，它不同于HashSet的根本就是TreeSet是有序的。它是通過SortedMap來實現(xiàn)的。
Set總結：
1、Set實現(xiàn)的基礎是Map（HashMap）；
2、Set中的元素是不能重復的，如果使用add(Object obj)方法添加已經(jīng)存在的對象，則會覆蓋前面的對象； Set里的元素是不能重復的，那么用什么方法來區(qū)分重復與否呢? 是用==還是equals()? 它們有何區(qū)別? Set里的元素是不能重復的，即不能包含兩個元素e1、e2（e1.equals（e2））。那么用iterator()方法來區(qū)分重復與否。 equals()是判讀兩個Set是否相等。==方法決定引用值(句柄)是否指向同一對象。
HashMap、TreeMap、Hashtable：
1、HashMap也用到了哈希碼的算法，以便快速查找一個鍵，TreeMap則是對鍵按序存放，因此它有一些擴展的方法，比如 firstKey(),lastKey()等。
2、Hashtable：不允許空（null）鍵（key）或值（value），Hashtable的方法是Synchronize的，在多個線程訪問 Hashtable時，不需要自己為它的方法實現(xiàn)同步，而HashMap 就必須為之提供外同步。 Hashtable和HashMap采用的hash/rehash算法都大概一樣，所以性能不會有很大的差異。
3、HashMap和Hashtable的區(qū)別：HashMap是Hashtable(線程案例的)的輕量級實現(xiàn)（非線程安全的實現(xiàn)），他們都完成了Map接口。主要區(qū)別在于HashMap允許空（null）鍵（key）或值（value）,非同步，由于非線程安全，效率上可能高于Hashtable。
Map總結：
是一種把鍵對象和值對象進行關聯(lián)的容器，Map有兩種比較常用的實現(xiàn)： HashTable、HashMap和TreeMap。