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  MaxHeapSize in JVM

MaxHeapSize is an option which is to set the JVM maximum heap size can be allocated. We can specify the MaxHeapSize as VM argument when we run the program by setting -XX:MaxHeapSize=, here can be 2M, 20M, 200M etc. We can also view the current MaxHeapSize set by setting different JVM options. To view the MaxHeapSize, we can use two JVM options : -XX:+PrintFlagsFinal and -XX:+PrintCommandLineFlags. Below is one example when running -XX:+PrintFlagsFinal: bool MaxFDLimit ...

   JVM,MaxHeapSize,Alignment     2014-06-17 07:01:50

  How to undo git changes?

When using git for version control, there is frequent need on undoing commits due to some unexpected changes. This post will introduce how to undo changes with git command in different cases. Undo commit A common undo case is that some commit needs to be reverted as the commit contains error. In this case, the code is already committed. The command to revert the commit is git revert HEAD This command will add new a commit to the existing head to undo the previous commit. It will not change the p...

   GIT,GIT RESET,GIT REVERT,GIT CHECKOUT     2019-12-28 02:21:47

  Python and PLC Communication

This article provides detailed steps on how to use Python to communicate with Schneider M221 and Siemens S7-1200 PLCs via Ethernet. Additionally, we offer a packaged Python PLC client library, enabling you to easily build your own SCADA control programs, such as Human-Machine Interfaces (HMI). The system overview is shown below: To check the project detail please refer to Python Physical PLC Communication Clients # Created: 2024/06/29 # Version: v0.1.3 # Copyright: Copyright (c) 2024 ...

   PYTHON,PLC,COMMUNICATION     2024-06-30 02:21:17

  Why can System.out.println be used to exit while loop

Let's first take a look at one simple Java thread code snippet which is supposed to exit the while loop after the first loop run. public class StopThread { private static boolean stopRequested; public static void main(String[] args) throws InterruptedException { Thread backgroundThread = new Thread(new Runnable() { @Override public void run() { int i = 0; while (!stopRequested) { i++; } } }); backgroundThread.start(); TimeUnit.SECONDS.sleep(1); stopRequested = true; } } But the tr...

   JAVA,THREAD,VOLATILE     2018-12-21 19:25:54

  Install and setup vsftpd on AWS server

When developing websites, frequently we may need to upload source codes to the remote server. To ease of thew work, many website developers set up FTPs to upload the files. This post is a tutorial on how to install and setup vsftpd on a server. vsftpd is a very popular FTP service on Unix-like systems. Open command terminal, then install the vftpd by issuing command yum install vsftpd or sudo apt-get install vsftpd After installing the vsftpd, the config file needs to be updated based on the ope...

   FTP,vsftpd,AWS,Passive,Active     2015-02-02 02:20:27

  OT Power Grid System Development

Use PLC to Remote Control Circuit Breaker in Power Grid System Figure-00: Project Overview Diagram, version v0.0.2 (2024) Project Design Purpose: The objective of this project is to demonstrate how to utilize Programmable Logic Controllers (PLC) to remotely monitor and control circuit breakers within a power (grid/supply) system. Using a Schneider Electric circuit breaker, sensor, closer and PLC, the project will cover the physical hardware connections and provide a step-by-step guide for desig...

       2024-09-21 08:56:05

  9 Ways to Create Thread Pools with Java Executors

In Java, the Executors class provides a variety of static factory methods to create different types of thread pools. When learning about thread pools, the Executors class is indispensable. Mastering its usage, principles, and scenarios will enable you to apply it smoothly in actual project development. Here are some commonly used methods, which I will explain one by one: newCachedThreadPool(): Creates a cached thread pool. If a thread has not been used for 60 seconds, it will be terminated and ...

   TUTORIAL,JAVA THREAD     2024-07-19 23:07:09

  Sorry, I don't want to download your fucking app

You should not claim yourself as a mobile Internet service provider if your product doesn't have an App nowadays. The topic cannot get away from App when we talk on bus, restaurant. Recently it becomes a little bit quiet, but the app wind does not seem to stop, it seems every website may have an App. According to data released by Apple a couple of days ago, its application store app downloads already exceeded 50 billion. However some people are not happy with this.Some people created a blog ...

   App,Update,Force download     2013-05-19 02:50:02

  Short SASS tutorial

If you learned CSS before, you should know that CSS is not a programming language. You can use it to design webpage style, but you cannot use it for programming, i.e, CSS is what designer uses, not what programmer uses. Programmer may think that CSS is very troublesome, it has no variables, no conditional statements, it just allows line-by-line description of HTML elementsLuckily, CSS preprocessor appear which makes CSS programmable. The general idea of CSS preprocessor is using a programming la...

   CSS,SASS,programmable,variable,condition,comment     2012-06-22 08:38:18

  A simple tutorial about CSS flex property

CSS Flexbox is a layout module that makes it easier to create flexible and responsive layouts in CSS. It provides a simple and powerful way to align elements within a container and distribute space between them. To use flexbox, you need to set the display property of an element to "flex". You can do this by adding the following rule to your CSS: .container { display: flex; } The flex container will now have two main axes: the main axis and the cross axis. By default, the main axis runs horizo...

   JUSTIFY-CONTENT,FLEX,CSS     2022-12-25 06:44:34

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