How to Debug Java Code Online (Step-by-Step) Write Your Java Code Type or paste your Java code in the editor above. The syntax highlighting helps you spot issues immediately. Click Run (Ctrl+Enter) Press the green "Run" button or use the Ctrl+Enter keyboard shortcut to compile and execute your program. Check Output for Errors Review the output panel. Compilation errors show exact line numbers. Runtime errors include full stack traces. Trace with println() Add System.out.println() to print variable values at key points in your code for effective debugging. Read Stack Traces When runtime errors occur, the stack trace shows the exact method and line where the error originated. Make corrections directly in the editor and re-run. The entire compile-run cycle takes under 2 seconds.

Common Java Errors and How to Fix Them GDB vs Online Java Compiler Frequently Asked Questions GDB (GNU Debugger) primarily supports C/C++ debugging. Java has its own debugger called jdb. However, our online Java compiler provides debugging-like capabilities through output tracing, error analysis, and stack trace inspection — no installation needed. You can debug Java online using our free compiler. Write your code, use System.out.println() to trace variables, analyze stack traces for errors, and fix issues instantly — all in your browser. jdb is the Java Debugger included with the JDK. It allows you to set breakpoints, step through code, and inspect variables. Our online compiler provides similar functionality without any installation. Yes, completely free. No signup, no hidden charges, unlimited programs. Supports Java 8, 11, 17, and 21. Yes! Our online Java compiler is fully mobile-responsive. You can write, run, and debug Java code on any Android or iOS device with a web browser. Main online Java compiler — write, compile, and run Java code Java 17 Compiler Latest stable LTS — Records, Sealed Classes, Pattern Matching Learn Java from basics to advanced with 60+ tutorials Start with the classic first Java program