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Online Java compiler

Write Java code, add input if your program reads any, and press Run. Java 21, in your browser.

Java 21

Main.java

Input (stdin)

Output

Press Run (or Ctrl+Enter) to see the output here.

What it supports

Java 21 in your browser

Java 21 with the whole standard library (java.util, java.io, java.time, streams, records and more).
One source file. The class with the main method is compiled and run for you.
Standard input from the Input box, standard output and errors in the Output panel.
Each run stops after 5 seconds. Code up to 64 KB, input up to 16 KB.
No internet access and no files kept between runs.

Input

How to read input in Java

Programs that read from the keyboard get their input from the Input box. Type one value per line, then press Run. The program reads the lines in order, just as it would from a keyboard.

Scanner sc = new Scanner(System.in);
int n = sc.nextInt();        // first value
String word = sc.next();     // next word
String line = sc.nextLine(); // rest of the line

Tip: if the output is empty or the run stops after 5 seconds, the program may be waiting for input that is not in the box.

Questions

Frequently asked questions

Do I need to install Java to use this compiler?

No. Your code is compiled and run on our servers with Java 21, so a browser on a laptop or a phone is enough. To build bigger projects, install the JDK on your computer later.

How do I read input in Java here?

Type the input in the Input box, one value per line, and read it with Scanner(System.in) or BufferedReader. The whole box is given to your program as standard input when you press Run.

Why does it say "class Main is public, should be declared in a file named"?

Write one file with one public class that has the main method. Keep that class name the same as the one in the starter code, or remove the word public from the class line.

Learn

Learn Java step by step

This compiler is the same editor the Java course uses for its practice problems.

Open the Java course MentorNxt DSA 150

Looking for another language? Try the online Python compiler.