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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

  Different ways to pass query parameters in EmberJS

In EmberJS, one could pass query parameters when retrieving resources with store.query() method. But what if there is a requirement that one wants to pass query parameters when calling store.findRecord()? Or there is a requirement that one wants to pass query parameters to a relationship when calling model.get('hasManyAttribute') in a RESTful style? In this post, we will explain how these can be achieved. In the store.query() case, one could easily pass the query parameters by passing ...

   RELATIONSHIP,EMBERJS,QUERY PARAMETERS     2018-05-18 10:47:56

  Jelly Bean becomes the most popular Android OS

Google released the latest Android usage stats on Monday. Jelly Bean becomes the most popular Android OS for the first time. It takes 37.9% Android market share(32.3% from 4.1.x and 5.6% from 4.2.x). Ginegerbread is at the second place and it has 34.1% Android market share. This is a good news to many Android developers as they can use many new features provided in the new system if there are more and more users are using the new OS. Also if Google wants to attract news users, they have to enco...

   Android,Jelly Bean,Usage     2013-07-09 04:52:28

  Understanding database, instance and schema in Oracle database

Oracle database is the most popular database system among enterprises. To start working on Oracle database, some concepts must be understood first. They include database, instance, schema and user etc. And among these concepts, some have different meanings from those in other database systems such as MS SQL, MySQL, DB2. On the web, there are already some good posts which explain different concepts such as Ask Tom's database vs instances, Difference between database vs user vs schema. In this pos...

   DIFFERENCE,DATABASE,ORACLE DATABASE,INSTANCE,SCHEMA,USER     2016-12-14 23:30:56

  Mozilla releases a web identity system : Persona

Now almost every website requires the user to register, there are many benefits of registration for a website, such as retaining users, accommodating discussions, providing customized content and so on.But there is too much trouble if each site requires registration, right?Of course, users can also have their own way, for those less important sites, for example, using a unified user name, password and email so that you only need to remember one account. Then, we also see some advanced methods em...

   Mozilla,Persona,Security,ID     2012-09-28 12:02:25

  Java vs F#

Dr Cliff Click of Azul Systems, specialists in manycore JVM systems, recently published a blog post about the performance of Java compared primarily to C and C++ but also discussing C# and .NET. Three of Cliff's comments are of particular interest:Under the heading "Places where C/C++ beats Java for obvious reasons":"Value Types, such as a 'Complex' type require a full object in Java." - Dr Cliff ClickWhat Cliff forgot to mention is that .NET also provides value types and a far more compell...

   Java,F#,Performance,JVM     2012-03-07 05:07:31

  A plugin to update last_error in Delayed Job

delayed_job is a process based asynchronous task processing gem which can be ran at background. It will fork the specified number of processes to execute the tasks asynchronously. The task status is usually stored in the database so that it can be easily integrated into a Rails application where asynchronous job execution is desired. Normally when a job fails to execute or error occurs, it would save the error into the database with the column last_error. Ideally all these will be handled b...

   RUBY,RUBY ON RAILS,DELAYED JOB,LAST_ERROR     2017-11-18 13:05:49

  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

  Simple but Interesting Features of VS2010 and C# 4.0

IntroductionVS 2010 and C# 4.0 introduced so many new features. Here in this article, I try to cover some very simple, yet very useful features of both.1. Hiding the Selected Part of CodeMany a times, a situation arises when we want to hide a specified piece of code rather that hiding the entire region. This has become easier in VS 2010. Just select the part of the code that you want to hide and right click selectOutlining -> Hide Selection.Same way like a region code also gets collapsible an...

   VS2010,C#4.0,New feature,Walk through     2011-11-18 08:59:29

  JavaScript interview questions

This post will cover the JavaScript questions I have encountered and have seen during my programming career. They will mainly focus on vanilla JavaScript though there are lots of excellent frameworks out there and many people are using them in their daily work. this keyword this keyword is an very important but easy to confuse concept in JavaScript since it is always referring to the calling object of the function. 1. What will be the output of below code snippet? function User(name) { this....

   JAVASCRIPT,ALGORITHM,THIS,CLOSURE     2019-03-09 07:05:46