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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

  What is goroutine?

Casual Talk Golang is quite enjoyable to write, aside from the tedious if err != nil checks. One of the fundamental reasons for the joy is goroutine, a core feature of Golang. Understanding goroutines in detail is worthwhile, as they contribute significantly to the pleasure of working with Golang. So, let's talk about goroutines, hoping to provide some insights to the readers. TL;DR: We'll start by talking about assembling a computer, then delve into some concepts of the operating system, such ...

   EXPLANATION,GOLANG,GOROUTINE     2024-01-21 03:26:10

  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

  NIO vs IO in Java

Java 1.4 provides a new API for handling IO -- NIO. This is a non-blocking and buffer oriented IO API. Below are main differences between the NIO and IO in Java. IO NIO Stream oriented Buffer oriented Blocking IO Non-blocking IO N/A Using selector Stream oriented vs Buffer oriented The main difference is that IO is stream oriented where the data is read byte by byte and the data will not be buffered normally.This means there is no pointer to move forward and backward in the stream. I...

   JAVA,IO,NIO     2016-01-10 01:40:02

  new() and make() in GoLang

GoLang is a modern, statically typed, compiled programming language designed for building scalable, concurrent, and efficient software. It provides various built-in functions and features that help developers write concise and efficient code. Among them are the new() and make() functions, which may appear similar at first glance but serve different purposes in GoLang and are crucial for memory allocation and data initialization. In this blog article, we will explore the differences between the n...

   NEW,MAKE,GOLANG     2023-11-18 13:43:25

  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

  Android socket programming example

Socket is a kind of interface for different sides t communicate, it usually identified by an IP and a port. There are many server side software on a server and they would provide different service. Each server many create some sockets and bind them to some ports so that clients can listen to. Software on the Internet will exchange data though a bidirectional connection established. Each end of the connection has a socket created. In Java, Socket and ServerSocket are in java.net package, ServerSo...

   Android,Socket,Java     2013-05-11 22:17:16

  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

  Java Cipher encryption/decryption example

In Java, Cipher is the API for doing data encryption/decryption. Many cryptographic algorithms such as AES, DES, RC4 etc can be specified when creating Cipher instance. The Cipher instance calls the underlying algorithm specific implementation to do the actual encryption/decryption.  Before doing the encryption/decryption, a key needs to be created and it will be used to do the encryption/decryption. A sample program for performing all these is : import java.security.Key; import javax.cryp...

   Java, Java Security, Cipher, Example, Sample     2015-08-14 07:07:10

  Data as code

What is a good command line parser API? A good command line parser should consider below 5 aspects: Support convenient help information generation Support sub commands, for example, git has push,pull,commit sub commands. Support single character option, word option, flag option and option with parameter. Support default option, for example, if no -port is set, set it as 5037 Support usage model, for example, tar's -c and -x is mutually exclusive, they belong to different usage models. Here are...

   Command line,API     2013-08-08 22:40:36