3 Java Interview Questions That Expose 90% of “Senior Developers”

Most developers can talk about microservices for hours. These three questions reveal whether they actually understand Java.

Harry

4 min read

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Jun 11, 2026

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A few years ago, I was interviewing candidates for a senior Java position.

The resumes were impressive.

“10+ years of Java.”
“Designed enterprise systems.”
“Expert in Spring Boot.”

Then I asked a simple question

What does volatile actually do?

Silence. A long silence.

Then came the classic answer

“It makes variables thread safe.”

No. It doesn’t.

That interview reminded me of something I’ve seen over and over again:

Many developers become experts in frameworks, cloud platforms, and architecture diagrams.

But surprisingly few understand the Java fundamentals that make those systems work.

If I had only 15 minutes to evaluate a senior Java developer, these are the three questions I’d ask.

And yes, they’re brutally effective.