How do you switch languages in your career?

I'm a senior python dev and I want to switch to something like Java but I don't have any professional experience with it. I've used it for some small projects and I know how to read and trace more complicated projects for the most part.

People say that you just need to know the basic programming concepts to make a switch and I agree with that, but how do I stand a chance against other candidates who have used Java for years?