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  Memory related exception analysis in Java

Java Virtual Machine Specification divides the memory of JVM into several areas : Heap, Stack, The Program Counter register and Method area etc. In HotSpot JVM, heap is composed of Young, Tenured and Perm. There are different OutOfMemory error can happen in different memory area. Next is an overview of some of these OOM errors. StackOverflowError The JVM will allow only a specified number of stacks created nested. An JVM option -Xss can be set to determine the maximum stack size. If the num...

   Java, Memory model, Memory exception, OOM     2015-01-19 06:54:27

  How many bytes a boolean value takes in Java?

Have you ever wondered how many bytes a boolean value takes in Java? One byte, this might be the answer comes out of your mind right away. But is it? Let's dig in more. Per Oracle documentation on boolean value definition, there is below statement: boolean: The boolean data type has only two possible values: true and false. Use this data type for simple flags that track true/false conditions. This data type represents one bit of information, but its "size" isn't something that's precisely defin...

   JAVA,INTERVIEW,SIZE,BOOLEAN     2020-02-29 02:49:18

  Big file transfer in Linux

It's very common that we need to transfer files between two different hosts such as backups. It is also an very simple task, we can use scp or rsync to complete the task well. But what if the file is very big, it may take some time to transfer it. How can we transfer a big file with high speed? Here we propose one solution. Copy file If we copy one uncompressed file, then we should follow below steps: Compress data Send it to another host Uncompress the data Verify the data integrity This will...

   Linux, SCP,ZIP     2013-01-10 05:55:50

  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

  Handle NXDomain error when resolving IP address in Ruby DNS resolver

In another post, we covered how to resolve SystemStackError when resolving IP address in Ruby. In this post, we would cover another common issue where a NXDomain error is returned when resolving an IP address. The NXDomain error means that the queried domain name does not exist in the DNS. In Ruby, DNS resolver library will use /etc/resolv.conf by default get the name servers to resolve the domain name. There are multiple DNS name servers can be specified in /etc/resolv.conf with below format. ...

   RUBY,RUBY ON RAILS,NETWORK,DNS,NXDOMAIN     2017-07-16 01:39:23

  Let's talk about JSON.stringify()

JSON has been used in lots of places to exchange data among different services/systems. Nowadays all mainstream programming languages have built-in library support of JSON data parse and stringify. In this post, let's talk about JSON.stringify() in JavaScript. Let's first take a small example of Object conversion handling. There is a requirement to convert below object const todayILearn = { _id: 1, content: '今天学习 JSON.stringify()，我很开心！', ...

   JAVASCIPT,JSON,JSON.STRINGIFY     2020-02-22 04:25:08

  Send email from Ubuntu command line

First install exim4 and exim4-config using the package manager then install mailx sudo apt-get install mailutils and follow the prompts once this is set up use the command “mail” to check your mail. if you would like to send mail type “mail” followed by the email address to mail it to eg mail me@examplecom enter the subject and press enter the body and keep pressing enter as many times as you need to, when your body is finished, press “Ctrl” and “D" toge...

   Ubuntu,Email,Command line,mailutils     2011-04-25 15:58:10

   How to Calculate Distance in Asp.Net MVC with Google Maps

Internet users are vastly dependent on both Google and Bing mapping tools. The API available for developers provides them an ability to add value to the solutions developed by them.There is no such requirement of using everything. There are times when only a snippet can make a big difference to the app users. In this article, asp.net development experts will explain how to use Google Maps APIs and help office staff to calculate distance. When a team is travelling for the job, they either ride on...

   ASP.NET MVC     2017-03-10 06:29:23

  4 asynchronous programming methods in JavaScript

You may know the execution environment of JavaScript is single threaded. The so called single thread means only one task can be running at any time, if there are many tasks, they need to be in a queue and wait for the previous task to be completed. The advantage of this mode is it's easy to implement and the execution environment is relative simple; the disadvantage is that if one task takes long time, the tasks following it must wait in the queue and this will delay other tasks consequently. Th...

   JAVASCRIPT,ASYNCHRONOUS PROGRAMMING, EVENT MODEL,PROMISE     2012-12-25 00:55:47

  Resolve SystemStackError issue when resolving IP address in Ruby

In Ruby, Resolv is the default DNS resolution implementation. It can be used to resolve IP address of a hostname. To use it, one just needs to require 'resolv' in the code. But sometimes, a user would want to check /etc/hosts first or some other mechanisms to resolve an IP address. In this case, one can require 'resolv-replace' and then replace the default DNS resolvers with customized DNS resolvers. For example, using resolv-replace, one would write require 'resolv-replace' Resolv::DefaultResol...

   RUBY,RUBY ON RAILS,NETWORK     2017-07-08 09:54:35

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