What is the Difference Between Java and JavaScript?

New developers often run into threads where someone asks why Java and JavaScript sound related yet behave so differently in projects. The names are confusing, but the two languages serve distinct purposes and ecosystems.

What is the difference between Java and JavaScript?

I see both mentioned in job postings and tutorials. Are they related, interchangeable, or meant for different things? I would love a straightforward comparison with examples and advice on when to choose one over the other.

Despite similar names, Java and JavaScript differ in design goals, runtime environments, and typical use cases. Here is a concise breakdown, plus code to illustrate how each one feels in practice.

• Type system. Java is statically typed and compiled to bytecode. JavaScript is dynamically typed and interpreted or JIT compiled.
• Runtime. Java targets the JVM across servers, desktops, and Android. JavaScript runs primarily in browsers and on servers via Node.js.
• Concurrency. Java uses threads, executors, and modern constructs like virtual threads. JavaScript uses an event loop with async callbacks, promises, and async/await.
• Deployment. Java builds JARs or WARs and runs on a JVM. JavaScript ships as scripts to the browser or as Node.js modules on a server.
• Typical use. Java is common for backend services, Android apps, and large-scale enterprise systems. JavaScript is the language of the web UI and also powers full-stack development via Node.js, but is quickly becoming adopted across all types of services.

Java: Strongly typed, class-based, main entry point.

// Java 17+
public class Main {
  public static void main(String[] args) {
    System.out.println(greet("Ada"));
  }

  static String greet(String name) {
    return "Hello, " + name + "!";
  }
}Code language: JavaScript (javascript)

JavaScript: Dynamic, functions are first-class, runs in browser or Node.js.

// JavaScript (Node.js or modern browser)
function greet(name) {
  return `Hello, ${name}!`;
}
console.log(greet("Ada"));Code language: JavaScript (javascript)

Java async using CompletableFuture:

import java.util.concurrent.CompletableFuture;

CompletableFuture.supplyAsync(() -> "data")
  .thenApply(d -> d.toUpperCase())
  .thenAccept(System.out::println);Code language: CSS (css)

JavaScript async using fetch and async/await:

async function fetchData(url) {
  const res = await fetch(url);
  const json = await res.json();
  return json;
}
fetchData("https://api.example.com/data").then(console.log);Code language: JavaScript (javascript)

• Choose Java for JVM performance, type safety, large codebases, Android development, and strong tooling on the server side.
• Choose JavaScript for web UI interactivity, full-stack flexibility with Node.js, and rapid prototyping with a vast package ecosystem.

• Java: Maven or Gradle produce JARs; deploy to JVMs or containers.
• JavaScript: npm or pnpm manage dependencies; ship bundles to browsers or run with Node.js.

Filter a list of items by a field.

// Java
import java.util.List;
import java.util.stream.Collectors;

record Item(String type, int score) {}

List<Item> items = List.of(
  new Item("a", 10),
  new Item("b", 20),
  new Item("a", 30)
);

List<Item> onlyA = items.stream()
  .filter(i -> "a".equals(i.type()))
  .collect(Collectors.toList());

// JavaScript
const items = [
  { type: "a", score: 10 },
  { type: "b", score: 20 },
  { type: "a", score: 30 }
];

const onlyA = items.filter(i => i.type === "a");Code language: JavaScript (javascript)

After you pick a language, you often need to handle images and video. Cloudinary helps with upload, transformations, and fast delivery to improve Core Web Vitals. Thankfully, Cloudinary offers Node.JS, JavaScript, and Java SDKs to fit any tech stack.

import com.cloudinary.Cloudinary;
import com.cloudinary.utils.ObjectUtils;

Cloudinary cloudinary = new Cloudinary(ObjectUtils.asMap(
  "cloud_name", "YOUR_CLOUD",
  "api_key", "YOUR_KEY",
  "api_secret", "YOUR_SECRET"
));

cloudinary.uploader().upload("path/to/image.jpg", ObjectUtils.asMap(
  "folder", "samples",
  "use_filename", true
));Code language: JavaScript (javascript)

const { v2: cloudinary } = require("cloudinary");

cloudinary.config({
  cloud_name: "YOUR_CLOUD",
  api_key: "YOUR_KEY",
  api_secret: "YOUR_SECRET"
});

async function upload() {
  const res = await cloudinary.uploader.upload("path/to/image.jpg", {
    folder: "samples",
    transformation: [{ width: 800, crop: "scale" }]
  });
  console.log(res.secure_url);
}
upload();Code language: JavaScript (javascript)

Whether you build in Java or JavaScript, pairing correct asset delivery with modern frontend practices improves user experience and performance at scale.

• Java is statically typed and JVM based, great for large backends and Android.
• JavaScript is dynamically typed, browser native, and ideal for interactive UIs and Node.js services.
• They are not the same language. Choose based on runtime, team skills, and project needs.
• For media-heavy apps, optimize delivery and formats early to avoid slow pages.

• PNG to WebP Converter
• Image Upscaling and Quality Enhancement
• Video as a Service Guide
• WEBM to MP4 Converter

Ready to optimize media in your Java or JavaScript apps? Create a free Cloudinary account and start delivering faster, higher quality experiences today.