Advanced IntelliJ IDEA Debugging Techniques: Evaluate and Log, Field, Exception, and Method Breakpoints

Adding Log at Breakpoints

Many developers use print statements for debugging, which often remain in code and cause extra work during code review. IntelliJ IDEA’s “Evaluate and Log at Breakpoints” feature allows you to log expressions without modifying the source.

public static void main(String[] args) {
    ThreadLocalRandom random = ThreadLocalRandom.current();
    int count = 0;
    for (int i = 0; i < 5; i++) {
        if (isInterested(random.nextInt(10))) {
            count++;
        }
    }
    System.out.printf("Found %d interested values%n", count);
}
private static boolean isInterested(int i) {
    return i % 2 == 0;
}

By pressing Shift + left‑click on a line, you can open the “Evaluate and Log” dialog, enter an expression such as "interested" + i , and run the program in Debug mode to see the logged values without adding explicit print statements.

interested 7
interested 5
interested 1
interested 2
interested 0
Found 2 interested values

Enabling the “Breakpoint hit” message shows the location of each breakpoint, and checking “Stack trace” provides a full call stack.

Field Breakpoints

When reading source code, you may need to know where a field’s value changes. IntelliJ IDEA lets you add a breakpoint on a field and select “Field access” or “Field modification” to pause execution whenever the field is read or written.

Optionally, you can add a condition in the “Condition” box to filter when the breakpoint triggers.

Exception Breakpoints

To stop execution before an exception is thrown, use Exception Breakpoints. Choose the exception type (e.g., NumberFormatException ) and the IDE will pause at the point where the exception is about to be thrown, showing variable values.

Method Breakpoints

You can also set breakpoints on interface methods (e.g., cmd+F8 or ctrl+F8 ) and configure conditions. When debugging, the IDE will jump directly to the concrete implementation that is invoked.

Conclusion

These four debugging techniques—evaluate‑and‑log, field, exception, and method breakpoints—help developers debug Java applications more efficiently, whether working on daily tasks or reading source code.