Far far less than Java jobs.
>Rails is more fun than Java, so if you're looking to expand your career opportunities, you're probably better off learning a tech stack that won't bore you to death.
Rails and CRUD web apps bore most hackers to tears.
At least with Java you can work from web apps, to Android, to web services, create powerful servers like Cassandra or powerful stuff like Solr and Lucene, use embedded Java, and a lot more.
Especially in middle America, or corporate America.
And far far far far less than .NET jobs. Which is still more fun than Java.
> Rails and CRUD web apps bore most hackers to tears.
They don't bore me to tears. Between the brand new Javascript frameworks like Angular and CSS frameworks like Bootstrap, it's possible to develop great looking, simple apps that have a great deal of functionality in extremely short amounts of time.
Java / Python / C# / Go... All the same.. I spend more time solving a problem than actually coding.
Once I have a solution rewriting in an another language is a piece of cake.
I think Java does suffer from a little too much boilerplate, but that is solved by becoming proficient in an IDE which doesn't actually take too long. Even for this old hacker who only picked up an IDE 2 years ago after nearly 20 years of emacs.
Depends where you are. Outside Silicon Valley and a handful of tech hubs in the world, Rails pretty much doesn't exist. Java, on the other hand, is used everywhere.