Sure I know other languages: Shell Scripting, Perl, HTML/CSS/JS, Groovy, SQL, C#, etc, but 80 percent of the code I write is in Java. I'm at a Java shop and have golden handcuffs. It's Java or bust for me.
Don't doubt yourself. There are a lot of great companies hiring Java developers; you don't have to worry yourself about the standard YCombinator group.
I found it difficult to pick up Clojure and Haskell "in a few days" when all I had was experience in those types of languages. In fact, mastering each of those languages requires a change in thinking that can only occur over a much longer time.
I did do some non trivial work in Lisp in a graduate class, but its not the same as using it all day. I don't believe I would seek out an opportunity where a Lisp dialect was the programming language of choice, anyway...
(I found ML to be easier to work with than Lisp. I guess it's technically not a pure functional language though).
I'm also working mostly in Java recently, and our project has a small amount of Scala (left over form and engineer long since gone). I am finding it really hard, on the rare occasions when I need to work on the Scala part, to get my head around it. I know I need a week or two to "get" Scala - but I just can't justify the time.
Sure I know other languages: Shell Scripting, Perl, HTML/CSS/JS, Groovy, SQL, C#, etc, but 80 percent of the code I write is in Java. I'm at a Java shop and have golden handcuffs. It's Java or bust for me.