Javascript to Java

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Transform your code from Javascript to Java with our free AI-based code convertion tool. If you like what you see, we also create documentation for your code! We don't ever store your code or any representation of it in our databases, but it will be shared with the LLM of our choice for processing.

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How to convert from Javascript to Java

When transitioning from JavaScript to Java, there are several differences you need to account for to ensure your code translates effectively. This guide will help you dissect and understand the crucial steps and considerations when converting from JavaScript to Java.

Understanding the Fundamentals

Syntax Differences

JavaScript and Java are fundamentally different in their syntax and structure, despite their similar names. JavaScript is a dynamically-typed, interpreted language primarily used for web development. On the other hand, Java is a statically-typed, compiled language commonly employed for building large-scale applications.

Variable Declarations

JavaScript Variable Declarations

In JavaScript, variables are declared using var, let, or const.

// JavaScript
let age = 25;
const name = "John Doe";

Java Variable Declarations

In Java, you need to specify the type of variable being declared, such as int, String, etc.

// Java
int age = 25;
String name = "John Doe";

Functions and Methods

JavaScript Functions

JavaScript function declarations are quite straightforward:

// JavaScript
function greet(name) {
    return `Hello, ${name}!`;

Java Methods

In Java, functions are typically declared within classes and are often called "methods."

// Java
public class Greeter {
    public String greet(String name) {
        return "Hello, " + name + "!";

Classes and Objects

Creating Classes in JavaScript

With the advent of ES6, JavaScript adopted class-based syntax, which is somewhat similar to Java:

// JavaScript
class Person {
    constructor(name, age) { = name;
        this.age = age;

    sayHello() {
        return `Hello, my name is ${}`;

Creating Classes in Java

Java has always been a class-based language:

// Java
public class Person {
    private String name;
    private int age;

    public Person(String name, int age) { = name;
        this.age = age;

    public String sayHello() {
        return "Hello, my name is " +;

Handling Asynchronous Operations

JavaScript often handles asynchronous operations with promises and async/await syntax:

// JavaScript
async function getData() {
    let response = await fetch('');
    let data = await response.json();
    return data;

In Java, the CompletableFuture class can be used for asynchronous programming:

// Java
import java.util.concurrent.CompletableFuture;

public class AsyncExample {
    public CompletableFuture<String> getData() {
        return CompletableFuture.supplyAsync(() -> {
            // Simulating an async call
            return "async data";

Error Handling

In JavaScript, errors are typically handled using try...catch blocks:

// JavaScript
try {
    throw new Error("Something went wrong!");
} catch (error) {

Java uses a similar approach but distinguishes between checked and unchecked exceptions:

// Java
try {
    throw new Exception("Something went wrong!");
} catch (Exception e) {


Converting from JavaScript to Java involves significant changes, especially with regards to typing, class structure, and error handling. Understanding these fundamental differences will aid in creating an effective and seamless transition from JavaScript to Java.

This free JavaScript to Java code converter guide should assist you in making the technical leap from one language to another with greater ease and clarity.

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