What’s the difference between Java and JavaScript?

Java and JavaScript are among the most known and most used programming languages. Unfortunately, the similarity in the language name often causes confusion. The following article highlights some of the differences and similarities between these two programming languages.

Java and JavaScript History

Java is a compiled and object-oriented, general-purpose programming language, first released in 1996 at Sun Microsystems and later acquired by Oracle. James Gosling created it, by accident, a few years earlier, and it was first named Greentalk and then Oak. C++ and C influence Java, and all code is written inside classes.

JavaScript was created as an interpreted scripting cross-platform high-level language by Brandon Eich at Netscape to make web pages more dynamic and interactive. It is contained within a webpage and embedded in HTML. It was initially named LiveScript and later renamed JavaScript due to a deal between Sun Microsystems and Netscape. Javascript refers to first Netscape’s and later Mozilla’s implementation of the language. The standardized version is called ECMAScript, and its versions are either called ES5, ES6 or ES2018, ES2019 and so on. In practice, most people simply call the language Javascript or JS. JavaScript is influenced by Java and to a lesser extent by other less known programming languages, Awk and Self. It also inherits from Perl.

Java vs JavaScript – Differences

Java and JavaScript are two very different languages. In this article, we compare certain areas of their uses and highlight some of the differences under the following headings:

• Code Execution
• Inheritance
• Concurrency
• Typing
• Usage

Code execution

Applications written in Java are platform-independent. The code is written and saved as a .java-file. The Java compiler translates this code into executable java-byte code and saves it as .class-files. The Java Virtual Machine can execute this code. The advantage is that code must only be written once and can still be run on any platform. The disadvantage is that Java is slower to start than other comparable programming languages but faster to run. 

JavaScript runs in the browser and does not have to be compiled. Every browser has a JavaScript interpreter that allows the execution of JavaScript code. In addition, it can interact with other elements that are not written in JavaScript.

Inheritance

Java uses class-based inheritance. All properties are part of the class and inherited by every instance of that class. Furthermore, multiple inheritances are supported, i.e. a class can derive properties from multiple classes. 

JavaScript is prototype-based. To establish hierarchy, an object can be assigned as a prototype with a constructor function. In contrast to Java, all objects can inherit directly from other objects. Multiple inheritances are not supported in JavaScript. Class construction has been enabled in version 5 of the ECMAScript standard, ES6.

Concurrency

Java supports multi-threading so that developers can work with multiple threads that maintain parallel concurrency at the price of high memory and processing requirements. 

JavaScript runs on a single thread. Concurrency is handled through a queue system (the event loop), and its features, e.g. async/await, callbacks and promises instead.

Typing

Java is strongly and statically typed. Types of variables and objects must be explicitly specified. Once a variable has been declared as a type, this variable’s type can’t be changed later, and it won’t be automatically converted into another type. However, implicit (automatic) conversions are run on primitive data types, e.g. an int type can be converted into a float type. Errors can be detected at compile-time instead of at runtime (static), and the code is rejected before it runs. This makes Java robust. Additionally, Java offers memory management, an automatic garbage collector, and exception handling.

JavaScript is loosely (or weak) and dynamically typed. Variables can be declared without assigning a data type to them, and variables can be reassigned to values with different data types. Types are checked during execution (dynamic), and errors at runtime may cause the whole program to stop working, and a type error gets logged to the console.

Java and JavaScript Usage

One special feature of Java is that there are four versions: 

• Java Standard Edition (Java SE)
  Lets users develop and deploy Java applications on desktops and servers. 
• Java Enterprise Edition (Java EE)
  Offers an enterprise software platform for developing server-side Java applications and allows the implementation of enterprise-class service-oriented architecture and Web 2.0 applications. 
• Java Micro Edition (Java ME)
  Focuses on the Internet of Things and the deployment of portable code for embedded and mobile devices. 
• Java Card
  Targets embedded devices and allows Java-based applications to be run on smart cards, e.g. ATM cards.

Developers use Java for various purposes: 

• Enterprise software 
• Android applications 
• Web applications (mostly server-side) 
• Big Data analytics 
• Scientific computing applications
• Operating System components,
• Games
• Embedded systems + Internet of Things 
• Social media platforms like Twitter 

Google’s Android operating systems use Java APIs. Worldwide, more than 3 billion devices use Java. 

JavaScript started as a scripting language for web browsers. A huge amount of libraries and APIs vastly extend its capabilities, and it has become an efficient multi-paradigm language that developers can use for object-oriented programming, procedural or scripting language. People us the term Vanilla JS for websites that do not use any libraries or frameworks and rely solely on the standard JavaScript functionality.

It now ranks among the best languages for building websites and is one of the big three core components of the web, next to HTML and CSS. Through the framework Node.js, developers can also use JavaScript for back-end development. It has gained access to the entire operating system, allowing JavaScript programs to read and write files, send and receive data over the network. Programmers can also use it for video game development, especially for applications that run in the browser.

Popularity

In the TIOBE Index, Java is third, while JavaScript ranks 7th.
The PYPL Index places Java in 2nd place, and JavaScript takes 3rd place.
In the IEEE Spectrum‘s annual interactive ranking, Java takes 2nd place, and JavaScript takes 5th place.

Scott Böning, Code Institute Student

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