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  Difference between ConcurrentHashMap and Hashtable


Both ConcurrentHashMap and Hashtable are Collection classes for storing key value pairs and they both provide fast element search with a supplied key. They have much in common. However, we will not discuss the similarities between them here, instead we will focus on the differences between them. ConcurrentHashMap and Hashtable are both thread safe. But the mechanism for thread safe is different between them. Hashtable is synchronized, it utilizes the synchronization mechanism; while ConcurrentHa...

   ConcurrentHashMap,Hashtable     2013-11-18 08:06:54


  Content based HTTP Cache


Browsers may cache the webpages we visited, when user types a URL on the address bar, the browser may cache the webpage returned from server while displaying it. If there is no update on the webpage, then next time when the browser requests the same page, it will not download the page again, instead it will load the cached page. If the website explicitly specify that the page is updated, then the browser will download the page again from the server. What's HTTP Cache? You may be familiar with th...

   HTTP Cache,Web crawler     2013-05-24 05:12:59


  Set PHP session timeout


There are many different discussions about PHP sessions. We may often face some weird issues while handling PHP sessions. Sometimes session is expired earlier than expected. Or sometimes the session is not expired. This introduces many confusions. Today we discuss how to set PHP session timeout correctly today. In php.ini, there are three key parameters which will affect the session timeout. session.gc_maxlifetime, session.gc_probability and session.gc_divisor. session.gc_maxlifetime defined the...

   PHP,session,timeout     2013-08-31 08:11:03


  What you may not know about PHP session


When we access one website, the site usually should have a mechanism to keep track of the status of the user on the site. There are a few mechanisms supported by many server side languages to help track user status such as session and cookie. Today we will talk about session, when creating a session, we need to keep track of many data, besides user data, we also need to tell the server what is the timeout of the session so that we can garbage collect the session data which should not be stored a...

   PHP session,session timeout,example     2013-07-06 08:44:18


  Introduction to DTLS(Datagram Transport Layer Security)


Secure communication has become a vital requirement on the Internet. Lots of information transferred through the Internet are sensitive data such as financial transactions, medical information, media streaming etc. To ensure security of data transferred on the Internet, a few secure protocols have been designed including SSL/TLS and IPsec. Many large websites in the world have adopted TLS. Apart from SSL/TLS, there is some other protocol designed to be used in special cases. One of them is ...

   JAVA 9,DTLS,TLS,SECURITY     2016-04-02 05:55:36


  Two things I don’t like about Hacker News


Hacker News is a very famous IT information hub. We can find many useful links about the latest IT news and fantastic technology demos. But there are two things I don’t like about Hacker News. Maybe some of you also have the same feelings.1.  About the more link. Every time we click the more link to go to next page, there will be a unique key generated to produce the new page. It is a good security mechanism. Also it may increase pages views as we need to read page by page but can...

   Hacker news,More link,Submission,Security     2012-02-28 11:55:37


  Prototypes and Object Orientation


David Chisnall takes a look at the two dominant paradigms in object-oriented languages (classes and prototypes) and discusses the strengths and weaknesses of each.Two terms are quite often confused when describing programming languages:class-based and object-oriented:Simula was the first class-based language. It provided classes (actually implemented using closures) as a means of encapsulating abstract data types.Smalltalk was the first object-oriented language. It provided a...

   Prototype,OOP,Differential,Comparison,Mo     2011-09-02 11:51:26


  PHP to get access token for Sina Weibo app


Previously I wrote two articles about getting access token for Facebook and Twitter apps using PHP. Today I will write one more article about getting access token for Sina Weibo app using PHP. OAuth 2.0 is now the authorization mechanism of Sina Weibo API. The API authorization process is similar to the process of Twitter. It has basically two steps: 1. Authorization; 2. Get access token. 1. Create an app. I hope you know how to create an app in Sina Weibo now. If not. You can access this page ...

   PHP,access token,Sina Weibo     2013-05-16 12:07:39


  Why does it take Task Manager longer to appear when you start it from the Ctrl+Alt+Del dialog?


Amit was curious why it takes longer for Task Manager to appear when you start it from the Ctrl+Alt+Del dialog compared to launching it from the taskbar. Well, you can see the reason right there on the screen: You're launching it the long way around. If you launch Task Manager from the taskbar, Explorer just launches taskmgr.exe via the usual Create­Process mechanism, and Task Manager launches under the same credentials on the same desktop. On the other hand, when you use the secure at...

   Windows,Task manager,Start time,Ctrl+Alt+Del     2012-02-02 07:06:56


  noConflict mechanism in jQuery


Many JavaScript frameworks like to use $ as function or variable name, jQuery is one of them. In jQuery, $ is just a reference to window.jQuery, so even if $ is deleted, window.jQuery will still be available to ensure the whole library can work normally. jQuery API design takes fully consideration of multiple frameworks conflicts, we can use jQuery.noConflict function to easily handle control. jQuery.noConflict accepts one optional boolean parameter[1] to determine whether to hand jQuery object ...

   jQuery,noConflict,$     2013-03-14 19:40:36