Java Online Compiler

How do I run Java code online?

Write your Java program in the editor, add standard input if your program needs it, and select Run. The output panel shows the result or an error message. You can also use Ctrl+Enter or Cmd+Enter to run your code.

The editor provides syntax highlighting and optional completion. The output panel displays errors reported when your program runs.

1. Start with the example below or replace the editor contents with your own Java code.
2. Open the input control and supply values in the order your program reads them.
3. Select Run and compare the output with the result you expected.
4. If execution fails, read the error, change the relevant line, and run the program again.

Try a Java example

// Java Online Compiler
// Write your Java code here

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

Why does my program fail or produce no output?

Check for syntax errors, missing input and a missing output statement. A program that reads input needs matching values in the input panel. Execution limits and the available runtime can differ from your local machine, so start with a small example before testing a larger solution.

What should I practise next?

Change the sample to test a calculation, a loop or a function. Try normal inputs and edge cases, including empty input and boundary values where they apply. Explain the expected result before running the code, then compare it with the actual output.