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  Why accessing Java HashMap may cause infinite loop in concurrent environment

HashMap in Java is frequently used to handle key/value pairs. But it is not a good candidate to be used in concurrent environment where ConcurrentHashMap should be used instead. If used in concurrent environment, it may cause lots of unexpected behavior even including make the program getting into an infinite loop situation. To understand how this can happen, let's first discuss how HaspMap works internally. In this post we will use implementation of HashMap before Java 8 as example, Java 8 prov...

   JAVA,HASHMAP,INFINITE LOOP     2020-03-29 01:47:00

  Use of log in programming

Usually, The purposes of log are for troubleshooting and displaying program running status. Good log will help us locate the error easier. Many programmers think log in programs is very simple, but it's not an easy task to write log codes to efficiently locate the error. Here we discuss about program log in three aspects: Where to log What to log Log styles to be avoided Where to log 1. When calling external functions When your program is calling some external functions which are not written b...

   Log, Programming,Debug     2012-11-28 11:42:23

  What is encryption? Its role in the modern age

“Messages and calls are end-to-end encrypted.” If you are a WhatsApp user, you must have read this statement at the top of chats you open. Now, what does it mean? The statement signifies that all the messages or voice notes shared between users are encrypted, and no one can read or listen in on them. As mostly all of us use messaging apps and emails, information security has become a major concern. Moreover, we don’t know how many digital footprints we leave on the web can be t...

   DATA SECURITY,VPN     2021-01-21 08:04:16

  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

  10 reasons why Dart is cooler than JavaScript

Dart is a new programming language from Google and after coding JavaScript for over one year now, I immediately felt in love with it. Coming from the Java world I had a good bunch of things I had to learn before I could use JavaScript. Some people say, you need to dig deep into JavaScript, otherwise you are not allowed to speak about the pros and cons of a language. I am not a JavaScript Ninja. But I strongly believe a programming language should be easy to learn, easy to understand and s...

   Dart,JavaScript,Comparison     2012-01-05 08:23:21

  The danger of target=_blank and opener

When want to open a new page in a new tab on clicking a link on a page, the usual way of achieving this is to use target="_blank" property in a tag. However, the use of this leaves space for phishing website. Background parent and opener Before talking about the opener object, let's know a bit about parent object when using iframe. HTML provides a parent object which is used to communicate between the parent page and the embedded iframe element. This parent object can be accessed using...

   HTML,TARGET BLANK,REL NOOPENER,REL NOREFERRER     2018-09-15 04:53:56

  Introducing the for-if anti-pattern

Over the years, I've seen a bunch of coding anti-patterns. I figured maybe I'll share a few. Today, I'll introduce what I'm calling the for-if anti-pattern, also known as "We'll sell you the whole seat, but you'll only need the edge." This is a special case of the for-case anti-pattern, where all but one of the cases is null. for (int i = 0; i < 100; i++) { if (i == 42) { do_something(i); } } This can naturally be simplified to do_something(42); The for-if anti-pattern arises in ma...

   Programming,Anti-pattern,for-if,efficiency     2012-02-02 10:18:15

  Python object creation sequence

[The Python version described in this article is 3.x] This article aims to explore the process of creating new objects in Python. As I explained in a previous article, object creation is just a special case of calling a callable. Consider this Python code: class Joe: pass j = Joe() What happens when j = Joe() is executed? Python sees it as a call to the callable Joe, and routes it to the internal function PyObject_Call, with Joe passed as the first argument. PyObject_Call looks at the ty...

   Python,Object creation     2012-04-16 15:03:55

  JavaScript as a First Language

At Khan Academy we've been investigating teaching Computer Science to students in some new and interesting ways. The most interesting aspect of which is that we're likely going to be teaching them JavaScript as their first language. We're in a very unique position as we're primarily aiming to teach students who've been through our previous math and science-centric curriculum. Because of this we can create some rather compelling exercises and projects that never would've been feasible other...

   JavaScript,Learning,First language,Inheritence,Prototype     2011-12-23 07:53:45

  Do NOT use boolean variable as function parameters

We follow lots of coding styles and coding standards when we do programming, but we may frequently forget one. The forgotten one is that do not use boolean parameter as the function parameters. The reason is it would greatly reduce the readability of the code. Don't believe it? When you read the following code, what does this code mean? widget->repaint(false); Do not repaint? Or what does this mean? After looking at the document, we know that this parameter is whether ...

   CODING STYLE,BOOLEAN,FUNCTION PARAMETER,CODING STANDARD,METHOD PARAMETER     2012-04-22 02:38:45

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