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  The Erlang Design Pattern

Over the last couple of weeks I did an OO programming experiment. I call it the Erlang design pattern. It is based on the Actor model but goes some steps further. At its core just like the Actor model there are active entities (objects) that have a thread and a message queue with the thread waiting on the message queue to do some stuff. The Erlang design pattern extends the Actor model by first dividing the software program into active (actors, that have their own thread) and passive ...

   Erlang,Thread,Pattern,OS Threads     2012-02-06 07:47:56

  The several flavors of random in Java

Random number generation is one of most basic features in any programming language. The basic utilization is always the same: generate a random number between 0 and 1. With such a simple resource at hand we sometimes overlook some interesting features. What do we learn from the books? The most obvious and maybe intuitive way to generate random numbers in Java is simply calling: java.lang.Math.random() Random generation is in the Math utility class with abs, pow, floor...

   Java,Random,Thread,Math,Type     2012-03-22 14:17:44

  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

  Deep Understanding of ReentrantLock: Unlocking the Mysteries of Java Concurrent Programming

ReentrantLock introduction ReentrantLock is a class in the Java concurrent package, java.util.concurrent.locks, and is an implementation of the Lock interface. As its name suggests, it is a reentrant mutual exclusion lock. A mutual exclusion lock is a synchronization tool used to protect shared resources, ensuring that only one thread can access the resource at a given time. Reentrant means that a thread can acquire the same lock multiple times without causing a deadlock. This lock provides some...

   JAVA,REENTRANTLOCK,CONCURRENCY,MULTITHREADING     2023-05-22 08:01:13

  IE ActiveX(”htmlfile”) Transport, Part II

In my last post I discussed using the ActiveX(”htmlfile”) technique to provide a usable streaming transport in Internet Explorer. The solution I provided will work, but since writing the last article I’ve made significant progress in understanding why IE behaves the way it does with respect to the streaming transport. The previous solution amounted to creating an array of messages, pushing messages on that array from the htmlfile iframe, and popping messages off of the array i...

   IE,Http,Streaming,htmlfile,Transport,Act     2011-09-05 04:07:02

  Workaround size limit of phpMyAdmin import sql file

When doing website development with MySQL, we often need to do database backup and restore. For website, the data in database will grow quickly, so when we back up the database, the size of the generated sql file may be over 80MB which is the max allowed size when we want to import a sql file for restoring our database using phpMyAdmin. To workaround this limit, we need to review the documentation of phpMyAdmin. Fortunately, I found an online article written by David Pratt  which gave us a ...

   MySQL,phpMySQLAdmin,80M,import,solution,limit     2014-08-14 09:59:27

  Use Java ThreadLocal with caution

According to Oracle documentation, ThreadLocal is a class provides thread-local variables. These variables differ from their normal counterparts in that each thread that accesses one (via its get or set method) has its own, independently initialized copy of the variable. ThreadLocal instances are typically private static fields in classes that wish to associate state with a thread. In short, ThreadLocal variables are variables belong to a thread, not a class or an instance of a class. One common...

   JAVA,MEMORY LEAK, THREADLOCAL     2015-11-03 07:31:57

  What can select do in GoLang

In Go language, select is a keyword used to listen to and perform IO operations related to channels. With the select statement, we can simultaneously listen to multiple channels and perform corresponding operations when any of the channels are ready. This article will summarize the common uses of the select statement and provide some considerations when using it. Basic syntax The basic syntax of the select statement is as follows: select { case <-channel1: // when channel1 has data to ...

   GOLANG,SELECT,USAGE,SYNTAX,TUTORIAL     2023-08-12 20:17:02

  Check whether a remote server port is open on Linux

As a system administrator or network engineer or application developer, there is a need to check whether a port on remote server is open so that you can tell whether the service under check is running or not. In this post, we would cover a few methods to check whether a remote server port is open or not on Linux. telnet telnet is the most frequently used command on both Windows and Linux to check port. The simple usage for this command is  telnet [host] [port] When the port is open, the o...

   LINUX,TELNET,PORT,NC,NMAP     2017-12-23 11:45:20

  JSP connect MySQL

To connect MySQL with Java Server Page(JSP). Some steps should be followed:Step 1: Download MySQL JDBC connector driver from the Internet. URL:  http://dev.mysql.com/downloads/connector/j/Step 2: Put the jar file downloaded in Step 1 in the Tomcat common lib folder and add this jar file to the CLASSPATH so that the JSP page can find the specified class.Step 3: Create the JSP page with MySQL connection : Example is shown below:        <% String driver="com.mysql.j...

   MySQL,JSP,Connection,Driver,Download     2011-05-11 10:04:57

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