Common Debugging Mistakes by Freshers
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The most common debugging mistake I see in freshers—and one I've made myself—is changing code without understanding the root cause.
When you see an error, there's this temptation to just try something and see if it fixes it. Maybe add a null check, maybe wrap it in a try-catch, maybe restart the application. But that's just guessing.
I learned this during a college project where I had a NullPointerException. I kept adding null checks everywhere until the exception went away. But I didn't understand why those objects were null in the first place.
Later, a teammate reviewed my code and pointed out I was calling methods on an object before it was initialized. The real fix was moving one line of code, not adding five null checks. Another common mistake is only reading the first line of error messages.
The stack trace shows the full execution path, and often the root cause is several method calls up from where the exception was thrown. I now read the entire stack trace to understand the call sequence. A third mistake is not verifying fixes with tests.
You change something, the error disappears, you move on. But you don't actually know if you fixed it or just masked it. Now I write a test that would have caught the bug before fixing it.
The test fails, I make my fix, the test passes. That proves the fix works and ensures the bug doesn't come back.
Common Debugging Mistakes by Freshers
Direct Answer
Common debugging mistakes freshers make include changing code without understanding the root cause, only reading the first line of error messages instead of the full stack trace, fixing symptoms rather than underlying problems, and not verifying fixes with tests. These mistakes waste time and often introduce new bugs.
Code Example
// Mistake 1: Fixing symptoms, not root cause
@RestController
class OrderController {
@Autowired
private OrderService orderService;
@GetMapping("/orders/{id}")
public Order getOrder(@PathVariable Long id) {
try {
return orderService.findById(id); // Throws NPE sometimes
} catch (Exception e) {
// BAD: Catching everything masks the real problem
return null; // Returns null instead of understanding why NPE occurs
}
}
}
// Mistake 2: Not checking assumptions
@Service
class OrderService {
public Order findById(Long id) {
// Assumes repository always returns non-null
return orderRepository.findById(id).get(); // Throws NoSuchElementException
}
}
// Better approach: Check assumptions, handle properly
public Order findById(Long id) {
return orderRepository.findById(id)
.orElseThrow(() -> new NotFoundException("Order not found: " + id));
}
Common Mistakes & Pitfalls
- Changing multiple things at once: Freshers make three code changes simultaneously, then can't determine which change actually fixed the bug or if the combination introduced new issues.
- Ignoring compiler warnings: Developers dismiss yellow warning highlights in the IDE assuming they're not important, but warnings often point to the exact assumptions causing runtime bugs.
- Not using version control effectively: Freshers fix a bug but don't commit with a clear message explaining what was wrong and why the fix works, losing valuable debugging knowledge.
- Debugging in production instead of locally: Junior developers try to debug issues directly in production environments instead of reproducing them locally with the same data, making debugging slower and riskier.
Check your understanding
Answer these without looking back at the article.
- How do you know when to ask for help vs keep debugging alone?
- How do you prevent bugs rather than just fixing them?
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