Build a Simple TCP Chat Room in Java

In this video we build a simple TCP chat room in Java.

Java is a general-purpose, class-based, object-oriented programming language designed for having lesser implementation dependencies. It is a computing platform for application development. Java is fast, secure, and reliable, therefore. It is widely used for developing Java applications in laptops, data centers, game consoles, scientific supercomputers, cell phones, etc.

📁 GitHub: https://github.com/NeuralNine

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Build a Simple TCP Chat Room in Java
Tyrique  Littel

Tyrique Littel

1600135200

How to Install OpenJDK 11 on CentOS 8

What is OpenJDK?

OpenJDk or Open Java Development Kit is a free, open-source framework of the Java Platform, Standard Edition (or Java SE). It contains the virtual machine, the Java Class Library, and the Java compiler. The difference between the Oracle OpenJDK and Oracle JDK is that OpenJDK is a source code reference point for the open-source model. Simultaneously, the Oracle JDK is a continuation or advanced model of the OpenJDK, which is not open source and requires a license to use.

In this article, we will be installing OpenJDK on Centos 8.

#tutorials #alternatives #centos #centos 8 #configuration #dnf #frameworks #java #java development kit #java ee #java environment variables #java framework #java jdk #java jre #java platform #java sdk #java se #jdk #jre #open java development kit #open source #openjdk #openjdk 11 #openjdk 8 #openjdk runtime environment

Zachary Palmer

Zachary Palmer

1555901576

CSS Flexbox Tutorial | Build a Chat Application

Creating the conversation sidebar and main chat section

In this article we are going to focus on building a basic sidebar, and the main chat window inside our chat shell. See below.

Chat shell with a fixed width sidebar and expanded chat window

This is the second article in this series. You can check out the previous article for setting up the shell OR you can just check out the chat-shell branch from the following repository.

https://github.com/lyraddigital/flexbox-chat-app.git

Open up the chat.html file. You should have the following HTML.

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>Chat App</title>
    <link rel="stylesheet" type="text/css" media="screen" href="css/chat.css" />
</head>
<body>
    <div id="chat-container">
    </div>
</body>
</html>

Now inside of the chat-container div add the following HTML.

<div id="side-bar">
</div>
<div id="chat-window">
</div>

Now let’s also add the following CSS under the #chat-container selector in the chat.css file.

#side-bar {
    background: #0048AA;
    border-radius: 10px 0 0 10px;
}
#chat-window {
    background: #999;
    border-radius: 0 10px 10px 0;
}

Now reload the page. You should see the following:-

So what happened? Where is our sidebar and where is our chat window? I expected to see a blue side bar and a grey chat window, but it’s no where to be found. Well it’s all good. This is because we have no content inside of either element, so it can be 0 pixels wide.

Sizing Flex Items

So now that we know that our items are 0 pixels wide, let’s attempt to size them. We’ll attempt to try this first using explicit widths.

Add the following width property to the #side-bar rule, then reload the page.

width: 275px;

Hmm. Same result. It’s still a blank shell. Oh wait I have to make sure the height is 100% too. So we better do that too. Once again add the following property to the #side-bar rule, then reload the page.

height: 100%;

So now we have our sidebar that has grown to be exactly 275 pixels wide, and is 100% high. So that’s it. We’re done right? Wrong. Let me ask you a question. How big is the chat window? Let’s test that by adding some text to it. Try this yourself just add some text. You should see something similar to this.

So as you can see the chat window is only as big as the text that’s inside of it, and it is not next to the side bar. And this makes sense because up until now the chat shell is not a flex container, and just a regular block level element.

So let’s make our chat shell a flex container. Set the following display property for the #chat-window selector. Then reload the page.

display: flex;

So as you can see by the above illustration, we can see it’s now next to the side bar, and not below it. But as you can see currently it’s only as wide as the text that’s inside of it.

But we want it to take up the remaining space of the chat shell. Well we know how to do this, as we did it in the previous article. Set the flex-grow property to 1 on the #chat-window selector. Basically copy and paste the property below and reload the page.

flex-grow: 1;

So now we have the chat window taking up the remaining space of the chat shell. Next, let’s remove the background property, and also remove all text inside the chat-window div if any still exists. You should now see the result below.

But are we done? Technically yes, but before we move on, let’s improve things a little bit.

Understanding the default alignment

If you remember, before we had defined our chat shell to be a flex container, we had to make sure we set the height of the side bar to be 100%. Otherwise it was 0 pixels high, and as a result nothing was displayed. With that said, try removing the height property from the #side-bar selector and see what happens when you reload the page. Yes that’s right, it still works. The height of the sidebar is still 100% high.

So what happened here? Why do we no longer have to worry about setting the height to 100%? Well this is one of the cool things Flexbox gives you for free. By default every flex item will stretch vertically to fill in the entire height of the flex container. We can in fact change this behaviour, and we will see how this is done in a future article.

Setting the size of the side bar properly

So another feature of Flexbox is being able to set the size of a flex item by using the flex-basis property. The flex-basis property allows you to specify an initial size of a flex item, before any growing or shrinking takes place. We’ll understand more about this in an upcoming article.

For now I just want you to understand one important thing. And that is using width to specify the size of the sidebar is not a good idea. Let’s see why.

Say that potentially, if the screen is mobile we want the side bar to now appear across the top of the chat shell, acting like a top bar instead. We can do this by changing the direction flex items can flex inside a flex container. For example, add the following CSS to the #chat-container selector. Then reload the page.

flex-direction: column;

So as you can see we are back to a blank shell. So firstly let’s understand what we actually did here. By setting the flex-direction property to column, we changed the direction of how the flex items flex. By default flex items will flex from left to right. However when we set flex-direction to column, it changes this behaviour forcing flex items to flex from top to bottom instead. On top of this, when the direction of flex changes, the sizing and alignment of flex items changes as well.

When flexing from left to right, we get a height of 100% for free as already mentioned, and then we made sure the side bar was set to be 275 pixels wide, by setting the width property.

However now that we a flexing from top to bottom, the width of the flex item by default would be 100% wide, and you would need to specify the height instead. So try this. Add the following property to the #side-bar selector to set the height of the side bar. Then reload the page.

height: 275px;

Now we are seeing the side bar again, as we gave it a fixed height too. But we still have that fixed width. That’s not what we wanted. We want the side bar (ie our new top bar) here to now be 100% wide. Comment out the width for a moment and reload the page again.

So now we were able to move our side bar so it appears on top instead, acting like a top bar. Which as previously mentioned might be suited for mobile device widths. But to do this we had to swap the value of width to be the value of height. Wouldn’t it be great if this size was preserved regardless of which direction our items are flexing.

Try this, remove all widths and height properties from the #side-bar selector and write the following instead. Then reload the page.

flex-basis: 275px;

As you can see we get the same result. Now remove the flex-direction property from the #chat-container selector. Then once again reload the page.

Once again we are back to our final output. But now we also have the flexibility to easily change the side bar to be a top bar if we need to, by just changing the direction items can flow. Regardless of the direction of flex, the size of our side bar / top bar is preserved.

Conclusion

Ok so once again we didn’t build much, but we did cover a lot of concepts about Flexbox around sizing. 

#css #programming #webdev 

Samanta  Moore

Samanta Moore

1620458875

Going Beyond Java 8: Local Variable Type Inference (var) - DZone Java

According to some surveys, such as JetBrains’s great survey, Java 8 is currently the most used version of Java, despite being a 2014 release.

What you are reading is one in a series of articles titled ‘Going beyond Java 8,’ inspired by the contents of my book, Java for Aliens. These articles will guide you step-by-step through the most important features introduced to the language, starting from version 9. The aim is to make you aware of how important it is to move forward from Java 8, explaining the enormous advantages that the latest versions of the language offer.

In this article, we will talk about the most important new feature introduced with Java 10. Officially called local variable type inference, this feature is better known as the **introduction of the word **var. Despite the complicated name, it is actually quite a simple feature to use. However, some observations need to be made before we can see the impact that the introduction of the word var has on other pre-existing characteristics.

#java #java 11 #java 10 #java 12 #var #java 14 #java 13 #java 15 #verbosity

Seamus  Quitzon

Seamus Quitzon

1602637135

Learning by Doing: How to Learn Java Basics by Building Your Own Project

Java is not the hardest language to start with. So, it becomes way popular among novice developers joining the ranks of Java coders every single day. If you are reading this blog post, you might be interested in learning Java.

Java is widely used across industry, and especially in the area of Enterprise software, which results in many high paying job opportunities and makes this programming language a common language for newbies. A general promotion of it within colleges and other institutions providing a formal Computer Science education also contributes to its popularity.

However, these are not the only advantages of Java — among other things, it allows you to adopt good practices and makes it way easier to learn other languages in the future. And with no doubt, you can easily learn it if you’re following the right approach. In this post, I am going to share some of them with you.

The Importance of Practice in Programming

Beyond all doubt, practice is important and valuable. But, before we get to the advantages of hands-on experience, I want to draw your attention to one essential thing I often tell my students.

New programmers who are just learning and start implementing things, without being supervised, often end up adapting bad practices. To avoid that, especially when you are making your first steps in programming, I recommend looking for a person who will supervise you and teach you. A strong mentorship with someone engaged in a serious project, as well as communication within the community in the form of sharing code and asking for feedback, is worth the effort. Similarly, when you are applying for your first job, you want to be looking for a company with a strong team and a good leader who would be keen on investing into your learning.

Now, let’s return to practical experience. Learning by doing is different from learning by passively consuming the information. To make sure we can use all the newly acquired technology, we should put our skills to test and write tons of code. The benefits of hands-on experience are almost endless.

Efficiency and Productivity

By practicing, you get a clear understanding of what programming is. Consequently, you start doing better with each new hands-on task, complete it faster, and thus become more productive.

Even if you are not working on real-world projects yet, it’s important to get used to having deadlines. They are inextricably linked to the programming process. My recommendation is to set up your own deadlines while practicing stage and follow them as closely as possible.

#java #learn java #java code #learn java in easy way #learn java course #learn java development

Samanta  Moore

Samanta Moore

1620462686

Spring Boot and Java 16 Records

In this article, we will discuss Java 16’s newest feature, Records. Then we will apply this knowledge and use it in conjunction with a Spring Boot application.

On March 16th, 2021, Java 16 was GA. With this new release, tons of new exciting features have been added. Check out the release notes to know more about these changes in detail. This article’s focus will be on Java Records, which got delivered with JEP 395. Records were first introduced in JDK 14 as a preview feature proposed by JEP 359, and with JDK 15, they remained in preview with JEP 384. However, with JDK 16, Records are no longer in preview.

I have picked Records because they are definitely the most favored feature added in Java 16, according to this Twitter poll by Java Champion Mala Gupta.

I also conducted a similar survey, but it was focused on features from Java 8 onwards. The results were not unexpected, as Java 8 is still widely used. Very unfortunate, though, as tons of new features and improvements are added to newer Java versions. But in terms of features, Java 8 was definitely a game-changer from a developer perspective.

So let’s discuss what the fuss is about Java Records.

#java #springboot #java programming #records #java tutorials #java programmer #java records #java 16