Java vs. JavaScript: 10 Major Differences

Java and JavaScript sound similar, and if you are new to the programming world, you might wonder if there is some sort of link between the two. Before I dive deep into the details, let me tell you what web developer Jeremy Keith says about the two – "Java is to JavaScript as ham is to a hamster".

Originally known as Mocha, JavaScript came into existence in 1995. It was known as LiveScript for a while, but later, upon receiving the license from Sun Microsystems, it came to be known as JavaScript.

The two languages are entirely different otherwise and have evolved quite differently. Both are very well known in the world of web development and programming.

In this article, I will discuss Java vs. JavaScript, their similarities, and differences.

Table of Contents

You can skip to a specific section of this Java vs. JavaScript comparison using the table of contents below:

What is Java?

Java is a programming language that is basically designed to run everywhere. Any application written in Java is compiled into bytecode that can run on implementations of Java Virtual Machine (JVM). JVM is the link between source code and the bytecode. Therefore, any machine with JVM can install and run Java. It is mostly used as a back-end programming language to build mobile apps for Android or web development. However, it also has front-end development applications as Java applets.

Java was first released in 1995 by Sun Microsystem and later acquired by Oracle corporation. It is one of the most used programming languages.

What is JavaScript?

JavaScript, along with HTML and CSS, are known as three major components of the web. JavaScript is a scripting language that runs in the browser and is employed by the majority of websites. It makes the web pages dynamic and interactive. Since the release of Node.js, it has also started to develop as server-side technology.

It can be used with other technologies like REST APIs, XML, and more. JavaScript is considered quite easy to learn and start coding with.

Similarities Between Java and JavaScript

Java and JavaScript are entirely different languages and therefore, there are many differences between the two. Before we discuss the differences, I will briefly talk about the similarities between Java vs. JavaScript.

1. Object-Oriented Programming (OOP)

Java and JavaScript are object-oriented programming languages and thus, run on basis of objects and their relation to each other. Therefore, both the languages implement encapsulation, polymorphism, and inheritance.

2. Used in Front-End Development

Both languages can be used in front-end development. Java can be used as Java applet while JavaScript can be embedded into HTML and implemented as a framework or library.

3. Used in Back-End Development

Both languages can be used on the server-side too. Java has been used for many years to power technologies like JBoss, Apache, and WebSphere. With the coming of Node.js, JavaScript-powered servers are also coming into existence.

Major Differences between Java and JavaScript

In this section, I will talk about what makes Java vs. JavaScript differences talk of the town. While the major difference is that Java was designed to be a general-purpose programming language and JavaScript was designed to build to interface with web technologies, here are more factors on which they differ from each other.

1. Running Platform

Java applications and programs run on Java Virtual Machine (JVM) that requires installing JDK and JRE on a system. However, JavaScript web applications run on a web browser and do not need any initial setup before running.

2. Mobile Applications

Most of the mobile applications, mainly Android ones, are written in Java. The Symbian system also supports Java. On the other hand, with the help of JavaScript, we can develop mobile applications but there are a few restrictions to that. It needs to use third-party tools like PhoneGap to convert the code to native programming code which can be executed.

3. Compilation

Java is a complete programming language and therefore, needs compilation and interpretation when running. JavaScript, however, is a scripting language that has plain text code and is only interpreted.

4. Learning

For Java, extensive documentation, online data sources, online forums, and communities are available for the learning process. Therefore, there is a lot of help available for those who want to learn and build Java programs and applications. For JavaScript, the process is comparatively easier as, in addition to a lot of documentation, online sources, and communities, the applications can be executed in the web browser immediately. This can help in seeing whether the application is running fine. Therefore, in addition to ease of learning, JavaScript can be easily, practically tested on the web.

5. Support

Java is a widely used language and almost every operating system supports it. That means, there is no need for conversion of the code to native code before implementation. JavaScript is supported by many web browsers and therefore, has support from many operating systems. There are rare chances when JavaScript will encounter compatibility issues.

6. Syntax

The syntax of Java language is similar to that of C or C++. It implements objects and classes. Here’s what a program in Java looks like:

class A {
 public static void main(String args[]){
 	System.out.println("Hello World");

The syntax of Java is similar to C programming language and naming conventions are similar to Java. However, it looks more like an HTML code.

	<title>My First JavaScript code!!!</title>
    	alert("Hello World!");

7. Scope

Java language is independent in its scope and can run on various operating systems. It uses block-based scoping where a variable is out of scope when the control is out of a block. That means a variable declared inside a class is available inside that class only. JavaScript is used on various web browsers and is entirely reliant on HTML and CSS, which is why it is not available globally. It uses a function-based scoping.

8. Concurrency

The ability to handle various instruction sequences all at once is different for Java and JavaScript. Java makes use of multiple threads and multiple tasks can be performed in parallel. However, JavaScript functions as Node.js in server-side applications. It handles concurrency using one main thread of execution through a queue system called the event loop and forking system known as Node Clustering. Both the methods work fine but Java is generally faster.

9. Typing

Java implements static type checking where the variables are checked at the time of compilation. A programmer needs to specify the type of variable they use. JavaScript is like most scripting languages that use dynamic typing where type safety is verified at runtime, which is why the programmer does not need to specify the variable type they create. Both the paradigms have their own advantages and disadvantages, but the main advantage of static type checking is that errors get caught early in the development phase. For dynamic typing, the advantage is that programmer can assign types as he wishes.

10. Inheritance

Java follows class-based inheritance while JavaScript follows prototypal inheritance. In Java, there is a top-down, hierarchical, class-based relationship where properties are defined in a class and inherited by an instance of that class. However, in JavaScript, the hierarchy is achieved by assigning an object as a prototype with a constructor function.

When to use Java?

You should choose Java for your project if it involves any of the following:

  • Android Apps
  • Big Data Analytics
  • Server-Side Technologies like Apache, JBoss, Geronimo, GlassFish, etc.
  • Enterprise Software
  • Scientific Computing
  • General Purpose Programming of Hardware

When to use JavaScript?

  • Dynamic single-page applications (SPAs)
  • Mobile App Development through PhoneGap, React Native, etc.
  • Server-Side technologies like Node.js, MongoDB, Express.js, etc.
  • Front-End technologies like jQuery, AngularJS, Backbone.js, Ember.js, ReactJS, etc. Both the above lists are to get you started. Keep in mind that both of these languages have more applications and you must assess your needs before you choose one.

    Disadvantages of Java

  • JIT compiler makes the program slow.
  • Due to the high memory and processing requirements of Java, the hardware cost is high.
  • Java has no support for low-level programming constructs such as pointers.
  • You do not have control over garbage collection in Java.

    Disadvantages of JavaScript

  • Client-side JavaScript does not allow you to read or write files for security reasons.
  • There is not much support available for networking applications in JavaScript.
  • It does not have multithreading or multiprocessing features.

Final Thoughts

This article gives you an overview of the comparison between Java and JavaScript. I advise learning both languages and becoming a full stack developer. Both the languages are different as one is mostly used at the back-end while the other is used at the front-end. Software development companies across the world are making use of both these languages to develop secure and scalable applications depending on the requirements.

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Written on September 12th, 2020