How do I know if it's time for me to say "I am an expert at Java (or any other programming language)"?

My personal opinion is that you should call yourself that when you no longer want to be taken seriously.  Your opinion of yourself doesn't matter.  What you've done matters.

You don't.  If you walk into an interview and claim to be an expert that's like "Challenge Accepted" to the technical interviewer.  You are setting yourself up for a world of pain. Instead approach things with a craftsmanship view and your coworkers will let it be known you are an expert... you won't have to say a thing.

I once worked as a small time 'chef' in a few kitchens.  Some of the most amazing Chef's I had the pleasure of working for never once said they were 'experts'.  The best among them always said that they didn't know anything about food.  We (the other works and I) were always flabbergasted why this person wouldn't be more proud of what they knew and had accomplished.  After all, they were running multi-million dollar a year restaurants.  Why not brag a little? The general lesson I've learned from them (and other 'experts' in different fields) is that the more you learn about a complicated subject, the more you'll realize that there's always going to be so much more to learn, and you'll always find someone that you can learn from.  Work to be great at something because you just want to be a badass with it.

The short answer is you should not say that; being an expert is a recognition from others, not a self-assessment. You can say "my expertise is in Java programming" - in this context it means your specialties. And you can certainly say that "I am proficient/skilled in Java programming", especially in interview contexts where it's your job to sell your skills. Anyone who calls themselves experts, even when others agree with them, can use a dose of humility that some people might just be happy to supply to them. The right way to approach building expertise is well summed up in the Parable of the Black Belt (Build to Last, Jim Collins) Picture a martial artist kneeling before the master sensei in a ceremony to receive a hard-earned black belt. After years of relentless training, the student has finally reached a pinnacle of achievement in the discipline. “Before granting the belt, you must pass one more test,” says the sensei. “I am ready,” responds the student, expecting perhaps one final round of sparring. “You must answer the essential question: What is the true meaning of the black belt?” “The end of my journey,” says the student. “A well-deserved reward for all my hard work.” The sensei waits for more. Clearly, he is not satisfied. Finally, the sensei speaks. “You are not yet ready for the black belt. Return in one year.” A year later, the student kneels again in front of the sensei. “What is the true meaning of the black belt?” asks the sensei. “A symbol of distinction and the highest achievement in our art,” says the student. The sensei says nothing for many minutes, waiting. Clearly, he is not satisfied. Finally, he speaks. “You are still not ready for the black belt. Return in one year.” A year later, the student kneels once again in front of the sensei. And again the sensei asks: “What is the true meaning of the black belt?” “The black belt represents the beginning — the start of a never-ending journey of discipline, work, and the pursuit of an ever-higher standard,” says the student. “Yes. You are now ready to receive the black belt and begin your work.” It's a never-ending journey that is its own reward.

Thanks for A2A. Well...you don't...:) you can be proficient in a language, but there will always be new features and better people so it is difficult to define 'expert'.

From Wikipedia: An expert ( http://upload.wikimedia.org/wikipedia/commons/a/a4/En-us-expert.ogg (http://en.wikipedia.org/wiki/Wikipedia:Media_help·http://en.wikipedia.org/wiki/File:En-us-expert.ogg)) is someone widely recognized as a http://en.wikipedia.org/wiki/Reliabilism source of http://en.wiktionary.org/wiki/technique or http://en.wikipedia.org/wiki/Skill whose faculty for judging or deciding rightly, justly, or wisely is accorded authority and status by http://en.wikipedia.org/wiki/Peer_group or the http://en.wikipedia.org/wiki/General_public in a specific well-distinguished domain.

Yeah, I agree with just about every comment I've read here: Don't go running around calling yourself an "expert." -- Looks funky. ========== Additional thoughts: I always laugh at attorney's who add "Esq" behind their name, and pretty much the same for anyone else such as MD or PhD, etc. If I see 5 years of "Java" on a resume -- I'm going to assume you've got some experience. I'll look at the education section if I want to know if you have a PhD or JD or MS, or BS, etc. Normally I'll overlook any resume where I see someone claiming expertise. ========== The only way you *really* know you're an expert is when you're regularly spending so much time coding that you're fixing, refining and eliminating crap code done by other experienced individuals. When you get to this level, you might be considered an expert, but don't go running around saying: "I'm an expert." -- In fact, you're probably spending your time DOING rather than concentrating on "am I an expert now, am I an expert now, are we there yet, are we there yet." You'll never really know if you're there if you're spending so much time looking at the lines on the road that you neglect the turnoff for the destination, and you don't know where that's at until you come up for air. And then most quality, supposed "expert" programmers just put their head back down into their work again. (They like challenges, not compliments; challenging them is the coveted complement -- saying: "You've got enough skill we can trust you with this.") Most of the supposed self-proclaimed "experts" I've run across are pompous fools who can hammer away at a keyboard and output crap, but, push-come-to-shove, couldn't put a man on the moon to save his (or her) life.... in other words, a lot of work done, but generally mediocre skills. I fix people's crap work all of the time. It doesn't make me an expert. (Though, it tends to make me a bit of an asshole, if you ask others.) Sometimes I read beautiful code that I would have never thought to write in such a way, but solves a problem beautifully -- no matter if you're an "expert" or not, you can come across such circumstances which make you feel tiny in the universe. Are you truly an expert then? It's purely a subjective state of mind. I also dislike the whole "brogrammer" / "Rockstar" engineer revolution and generation -- bunch of pompous fools with bad attitudes.

When people ask me whether I'm an expert at Java, I tell them "I don;t know whether you will call me an expert, but these are the things that I can do"