Java vs JavaScript - What is the Difference?

Even today many people are asking the question "What is the difference between Java and Javascript". But not only that. The two terms Java and JavaScript are often used as synonyms, being mistaken or simply thought of as the evolution of the other language, which is completely wrong.

Therefore, it is time to bring clarity to this matter once and for all. But before we take care of the differences between the programming languages Javascript and Java, let us find out what these two terms mean and what the languages are used for.

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What is Java

Java in this context is a class-based, object-oriented programming language and one of the most popular languages in the world. Together with the Java Development Kit (JDK) and the Java Runtime Environment (JRE) it forms the Java Technolgy. The runtime itself consists of several libraries and the Java Virtual Machine (JVM). It is important to know that the JRE can not only run bytecode compiled from Java but also from other programming languages like Scala, Groovy, or Kotlin (and theoretically from any other languages if a bytecode compiler exists for them).

Java applications are written in a form that humans can understand, the so-called source code. This source code cannot be run directly and needs to be compiled by the Java Compiler, which is part of the JDK, into bytecode that computers can understand. The machines running the bytecode are typically virtual machines. This means that the code isn't directly run by the hardware but by software on the target platform. This virtualization enables platform-independence, a big feature of Java. Applications written in Java can run on almost any device and computer architecture if a corresponding runtime environment is installed.

Who invented Java?

Java was originally invented by James Gosling in the early 1990s during his time at Sun Microsystems because he was not satisfied with the capabilities of C++. The first prototype was called Oak (Object Application Kernel) and it was targeted towards interactive television and other entertainment devices. The original compiler was written in C and shortly after the language was renamed to Java and the focus shifted to the World Wide Web.

Since 2010 Java belongs to the Oracle Corporation as part of the acquisition of Sun Microsystems.

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What is JavaScript

JavaScript is a scripting language that is standardized as ECMAScript and described as interpreted, dynamical typed, object-oriented but class-less. Since ECMAScript 6, JavaScript can compete with other object-oriented languages because of the introduction of prototypes. In JavaScript, one can write code either object-oriented, procedural, or functional - whatever fits best.

Who invented JavaScript?

In 1995, Brendan Eich created JavaScript (originally it was called LiveScript) during his time at Netscape with the purpose of dynamical HTML in web browsers to analyze user interactions and changing, generating, and updating content. Basically to extend the capabilities of HTML and CSS at that time.

What does js mean?

People often use the term js as an abbreviation of the term "JavaScript". Also, many libraries and frameworks like Next.js, Vue.js, or Reactjs use this to indicate that they are written in JavaScript.

Is JavaScript an interpreted language?

This is a question often raised during interviews for software engineering jobs. Originally JavaScript was designed as an interpreted, high-level and dynamic programming language. Interpreted in this context means that the source code can directly be executed by the interpreter, line by line. In contrast, Java (or C++) is a compiled language meaning that the source code cannot be run directly but has to be compiled into bytecode by a compiler before.

So many people are going to tell you that JavaScript is indeed an interpreted language as per the language specification. However, this isn't a definitive answer anymore. With the rise of the V8 engine that powers Google's Chrome Browser the clear differentiation between interpreted and compiled became somewhat blurry. V8 compiles the JavaScript source code into native machine code before executing it and other modern JS implementations like Rhino (which is actually written in Java!) or TraceMonkey do similar things.

So while JavaScript, in theory, is an interpreted language the actual implementations are using features of interpreters and compilers to combine the best of both worlds.

So is JavaScript an interpreted language? Yes. Is JavaScript a compiled language? Also yes. It's just a matter of perspective.

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What is Java used for

In general, the programming language Java is used to write code in a human-readable way that gets compiled into bytecode that runs on virtual machines on any kind of device. Especially with the rise of the Internet-of-Things, the numbers have skyrocketed. In fact, Java runs on billions of devices today. Due to its nature of being platform-independent, Java is also used for many applications.

Here are some examples:

• API backends
• Machine Learning backends
• Storage backends

• Processing backends in the financial industry

• Native Android Applications

• Industrial Control Systems

Big corporations use Java as a fundamental piece of their tech-stack. For example, most of Amazon's stack including AWS is based on and written in Java.

What does Java do?

Java as a programming language - as already said before - is used to write programming code that gets compiled and executed on machines. Java on your computer (and what this question often refers to) means the Java Runtime Environment, the JRE. It does nothing on its own but provides the infrastructure to run Java-based applications on your local computer or on virtual machines distributed over a network.

Do I need Java?

This question often relates to the question if you need to install Java on your computer. While it is not necessary to have it installed in general, many applications today rely on the Java Runtime Environment to function. So, if you want to install an application that is written in Java - yes, you need to install the Java Runtime Environment. But you don't need to install the JDK or have knowledge of the Java programming language for that! The main reason to know about the programming language Java is if you want to become a Java developer.

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What is Javascript used for

JavaScript makes websites interactive and powers web servers and APIs. While the usage of JS, in the beginning, was limited to browsers (the clients), as of today it can also be used on the server-side, for example using node.js. On websites, JavaScript handles things like submitting forms, validating user input, executing third-party scripts, calling APIs for data. In short, creating interactive applications. Without JavaScript, most websites would be what we call static websites.

Do I need JavaScript?

Almost all websites today need your browser to execute JavaScript to function properly. Without JS, there would be no Facebook, no Twitter, no Amazon, no Instagram...Basically, everything that is interactive on these websites is powered by JavaScript. While you can deactivate JavaScript in your browser it is not wise to do so because you won't enjoy a pleasant experience for the majority of websites anymore. There was a time when JavaScript was condemned as evil and people suggested to block its execution. But as of today, JavaScript is an integral part of the internet and modern browsers take care of all security-related aspects of executing JS.

Like with Java, you cannot install the programming language JavaScript on your computer. Some applications like web servers that are written in JS need a runtime environment, for example, node.js to work. But for the average user that's not necessary.

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What is the difference between Java and JavaScript?

I hope you already have gotten a good understanding of the differences between JavaScript and Java by now. Besides the name and both being programming languages, JavaScript and Java are fundamentally different. Java is mainly used to write applications that run on a virtual machine via the Java Runtime Environment. JavaScript is used to write code that gets mainly executed by a browser to create interactive websites and applications.

Java is a compiled, strictly typed language and JavaScript is an interpreted, dynamically typed language. However, as you've already read, the line between interpreted and compiled languages became somewhat blurry in the last years.

The syntax of Java is also quite different in comparison to the JavaScript syntax:

Java syntax

JavaScript syntax

Is Java short for JavaScript?

Absolutely not! Besides the similar name, these are two fundamentally different programming languages. The reason for this confusion and that it is still existing today is for a historical reason. Because there have been copyright issues with the original name of JS, LiveScript, Netscape decided to rename the language to JavaScript to profit from the popularity of Java at that time. But Java is actually much closer to C++ than to JavaScript.

What is a Java Developer?

A Java Developer is a software developer or engineer that specializes in or has some decent knowledge of the Java programming language to use it for writing applications with it. This can either be professional as part of their daily work or just as a hobby. Because Java is mainly used for writing server-side applications (the back-end) people are often referring to Java Developers as Backend developers.

Because many corporations all over the world use Java as a part of their tech-stack and the language itself is very popular, Java Developers are in high demand and in general well-paid.

What is a JavaScript Developer?

A JavaScript Developer is someone that knows how to write applications using the programming language JavaScript. The term "JavaScript Developer" is often used as a synonym for a software developer, a software engineer, or even a web developer. In the world of JavaScript people and companies often differentiate between JavaScript developers for the client-side (frontend developer) and the server-side (backend developer). Some even have job descriptions for React Developers or Vue Developers indicating that they are looking for engineers that know specific JavaScript frameworks.

Due to so many websites and applications running with JavaScript, web developers are in very high demand and generally well-paid. Because JS can be used on the client-side and the server-side, job opportunities are huge these days.

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Java vs. JavaScript - Which is better?

For this question, only one valid answer exists: It depends. Because the use cases and general conception of JavaScript vs. Java are so fundamentally different there really isn't one better than the other.

Java has some advantages over JavaScript and vice versa. Java is regularly taught as part of computer science degrees while JavaScript developers are often self-taught. And some people find JavaScript easier to learn general programming. But the best approach is to be open-minded about both languages and always decide on a per case basis.

• What language is the best for the project or company?
• Do I want to work on the client-side, server-side, or both (as a full-stack developer)?
• How many resources like learning materials, tutorials, courses, libraries, frameworks, etc exist for the languages?
• How does the job market in my country or city look like? Are there more jobs for Java or JavaScript developers available?

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Here is a great video for you that also explains some of the key differences!

So obviously no language is better than the other and the best way to learn either JavaScript or Java is to actually write code. And there are many resources available, some for free, some you have to pay to support your learning. If you are looking for projects that you can build with JavaScript, here are some great javascript projects. And if you are looking for a collection of programming books we got you covered as well!

This post was originally published on The Smart Coder by my friend Ann Fraser.

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