Java Online Compiler
Write, compile, and run Java code online directly from your browser with our free Online Java Compiler. Test Java programs, classes, methods, collections, and object-oriented concepts without installing the JDK or setting up heavy IDEs such as Eclipse or IntelliJ IDEA.
How to Use This Java Compiler
- Write or paste your Java code
Enter your program in the Code Editor. You can test variables, methods, loops, classes, arrays, collections, exception handling, and other Java features supported by the execution environment. - Click the Run button
Select Run to compile and execute your Java program on the configured JVM environment. If your code contains a compilation or runtime error, review the returned message, correct the relevant code, and run it again. - Check the Output screen
Your program output and compiler feedback appear in the Output panel. Use the available controls to copy, download, or delete the output before testing another program.
Key Features
- Free Online Java Compiler: Write and execute Java programs directly from a modern web browser.
- Zero Installation: No need to install the JDK, configure Java locally, or set up Eclipse, IntelliJ IDEA, or another desktop IDE for supported programs.
- Instant Compilation and Execution: Click Run and quickly view your program result or Java compiler errors.
- Standard Java Syntax: Practice classes, methods, loops, arrays, inheritance, interfaces, exceptions, generics, and other core Java concepts.
- Java Standard Library Support: Use commonly available packages from the Java standard library when supported by the configured runtime.
- Dark and Light Mode: Switch the Code Editor theme for comfortable coding in different lighting conditions.
- Output Controls: Copy, download, or clear generated output directly from the Output panel.
- Useful for Learning and Testing: Suitable for students, developers, interview preparation, algorithm practice, and quick Java code experiments.
1. How do I take user input using the Scanner class?
Java commonly uses Scanner from the java.util package to read standard input.
Enter the program in the Code Editor and click Run. Interactive input depends on how standard input is provided by the online compiler environment.
2. Do I need to install Java or the JDK to use this compiler?
No. You can use this Online Java Compiler directly from your browser without installing Java, the JDK, Eclipse, or IntelliJ IDEA for supported programs.
A local JDK may still be preferable for larger applications, Maven or Gradle projects, external dependencies, advanced debugging, and development that requires direct system access.
3. Why does my Java class need to be named Main in this environment?
Many online Java compilers use a predefined source file and execution command, so they expect the program entry class to be named Main.
For example:
If you rename the public class, the compiler environment may not find the expected entry point or may report a class/file-name mismatch.
4. Can I use Java standard library classes and packages?
Common classes from the Java Standard Library can generally be used when they are available in the configured JVM environment.
Third-party libraries, Maven/Gradle dependencies, database drivers, or platform-specific APIs may not be available unless the online environment explicitly provides them.