Souf | Java Interview Mentor
@SoufJavaMentor
I help Java developers pass technical interviews. 10+ years of real interviews → questions, traps & recruiter mindset. Java • Spring • Kafka
You can be a good Java developer and still fail interviews. Why? Because no one trains you on real interview questions. 10+ years of Java interviews. Here: real questions, traps, and recruiter mindset. 👉 Follow if you’re preparing a Java interview.
Java interview trap “Memory is stable. No OutOfMemoryError. The Garbage Collector is running.” The candidate says: 👉 “Everything looks fine.” Me: 👉 Then why is the app slow? 👉 How does the GC actually decide an object is dead? Still think everything is fine ?
I choose Spring boot every day. What about you guys ?
You can choose only ONE backend from this list. Which one are you picking and why?
Junior Java interview mistake 👇 “I overrode equals(), so it’s fine.” Then they use HashMap. And things break. They forgot hashCode(). This single mistake has eliminated many candidates. Have you seen this before?
What about you, how was your day 1 learning java ?
Java interview trap 👇 You see an exception in the try block and think that’s the end. It’s not. In try-with-resources, another exception can be thrown in close(). One exception wins. The other gets buried. Do you know which one — before an interviewer asks?
After 10+ years of Java interviews, one clear pattern: 👉 Rejections rarely come from a lack of technical knowledge. 👉 They usually come from poorly structured answers. That’s exactly what I help candidates improve.
🚨 Interview trap 👇 “HashMap is not thread-safe.” Many candidates suggest: 👉 Collections.synchronizedMap ⚠️ Bad idea in many cases: • contention • poor scalability 👉 ConcurrentHashMap exists for a reason. When would you still choose a synchronized map over…
With all these changes across OpenJDK projects, which ones do you think candidates should really understand for interviews?
2025 is coming to a close. 🕐 The latest Inside Java Newscast looks back at the highlights of the year, the current state of the six big OpenJDK projects, and more. social.ora.cl/6011COLiH
Most Java candidates forget one of these in interviews 👇 Happy path Edge cases Performance Thread-safety Which one do you usually miss?
What recruiters expect 👇 If you override equals() without overriding hashCode(): • HashMap • HashSet ➡️ inconsistent behavior ➡️ silent bugs in production 🎯 What they’re really testing: your understanding of Java collections.
Real Java interview case 👇 Why override equals() and hashCode()? “Because it’s the rule” ❌ 👉 That answer costs points. What would you say instead?
Quick question 👇 Java interview style: A️⃣ Talk a lot B️⃣ Short & precise answers C️⃣ Ask the interviewer questions The best choice isn’t obvious 😉 What’s yours?
🚫 Java interview myth: “If it compiles, it works.” ❌ Wrong. Interviewers care about: • understanding • edge cases • real-world behavior 👉 Code is only step one.
Frontend looks hard until you touch the backend.
In a Java interview, he answers fast. Too fast. Right concept. Wrong priority. The interviewer isn’t testing Java. They’re testing how you reason under pressure. Have you ever answered too fast in an interview?
In high-performance Java systems, a Full GC is often a red flag 🚨 Why? • stop-the-world pauses • unpredictable latency • CPU spikes • direct impact on SLAs 🎯 In interviews, recruiters expect you to talk about latency, not just “memory cleanup.”
✅ Réponse attendue par un recruteur 👇 HashMap.get() est : • O(1) en moyenne • O(n) en pire cas (collisions) • O(log n) depuis Java 8 (tree bins) 🎯 Ce qu’on évalue ici : ta compréhension des compromis internes, pas la récitation.
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