Welcome to HCODX Online Compiler
Quick Start:
Ctrl+Enter Run code
Ctrl+S Save / Download
Ctrl+L Clear output
Select a language and start coding.
Compile and run Java code online instantly with HCODX. Our free cloud-based Java compiler supports real-time execution, standard input, syntax highlighting, and code download. No installation or configuration required. Start coding in Java now.
Run Java instantly without installing any IDEs or configuring environments. Our cloud-based Java handles libraries, runtimes, and dependencies automatically so you can focus on writing code.
Whether you are studying algorithms in Java, practicing data structures in Java, or exploring functional programming, our tool provides real-time stdout/stderr feedback with interactive standard input support.
HCODX is a free online compiler and code runner: write code in your browser, execute it on a cloud sandbox, and interact with your program through a live terminal. Students use it for coursework and interview practice; developers use it to test snippets in 85+ languages without setting up a local environment.
Every AP Computer Science A exam and countless university CS1/CS2 sequences are taught in Java, and the language is just as entrenched in industry — Amazon, Netflix's backend, and nearly every major bank run critical systems on the JVM. Modern Java is far more expressive than its old reputation suggests: records, pattern matching for switch, text blocks, and virtual threads have all landed in recent LTS releases. This online Java compiler pairs a modern JDK with a real interactive terminal, meaning Scanner and System.in behave exactly as they do in IntelliJ or a local shell — your program prints its prompt, then sits and waits for you to type.
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number: ");
int n = sc.nextInt();
long fact = 1;
for (int i = 2; i <= n; i++) {
fact *= i;
}
System.out.printf("%d! = %d%n", n, fact);
sc.close();
}
}Run AP Computer Science A practice problems and university OOP assignments without wrestling with JDK installs or IDE licensing, solve LeetCode and HackerRank problems in the language most big-tech interview loops still accept by default, or confirm exactly what a String method, ArrayList operation, or integer overflow does before an exam. Because Scanner works against a live terminal, textbook exercises that read input interactively run unmodified — the same code your professor demonstrates in class works here verbatim. HCODX is a free online Java editor, runner and interpreter — an IDE-grade compiler and playground to write and run code online, execute code with live output and live preview, no downloads or web server required.
Fully. The sandbox attaches your program to a real terminal, so sc.nextInt(), sc.nextLine(), and hasNext() loops block for live keyboard input exactly like a local console application. You don't pre-load input into a text box — the program prompts, you answer, it continues.
A modern LTS-line JDK, so contemporary language features — var, records, enhanced switch expressions, text blocks, and the streams API — compile and run. If you're studying from an older textbook, all legacy syntax remains valid too; Java's backward compatibility is famously strict.
No — there's no dependency resolution in the sandbox, so external libraries like Gson, JUnit, or Apache Commons aren't available. Everything in the JDK itself is: collections, java.time, regex, concurrency utilities, and I/O. Your code should live in a single file with one public class.
Your current code will be replaced with the default sample. This cannot be undone — download your code first if you want to keep it.
You have unsaved changes. Do you want to save your code before continuing?