Advanced Debugging Techniques in IntelliJ IDEA for Java Developers

When developing Java projects, many developers are comfortable writing code in IntelliJ IDEA but lack deeper debugging skills beyond basic F7, F8, and F9 shortcuts. This guide presents several advanced debugging scenarios such as debugging specific values inside a for loop, multithreaded debugging, and modifying variable values at runtime.

1. Conditional Breakpoints – Useful for stopping execution only when a certain condition is met, e.g., pausing when a loop variable reaches a specific value. Right‑click the red dot of a breakpoint, select Condition , and enter the expression.

2. Drop Frame ("Back to Previous") – Allows you to revert the execution point to an earlier stack frame, effectively rewinding the call stack. Click the Drop Frame icon on a paused breakpoint to return to the start of the calling method.

3. Multithread Debugging – By configuring each breakpoint’s Suspend policy to Thread instead of All , you can isolate and step through a specific thread, preventing the debugger from jumping between threads unpredictably.

4. Remote Debugging – Enables debugging code running on a remote server without launching the project locally. First, start the Java application with debugging flags:

java -server -Xms512m -Xmx512m -Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=9081 -Djava.ext.dirs=. ${main_class}

Then configure an IntelliJ remote debugging configuration and attach to the specified port.

5. Evaluating Expressions / Changing Variable Values – While paused, click the + icon in the debugger to open an input field, type any expression (e.g., i+5 ), and press Enter to see the result instantly. You can also right‑click a variable and choose Set Value to modify it on the fly.

By mastering these five techniques, Java developers can dramatically improve their debugging efficiency, quickly locate bugs, and resolve issues with confidence.