It’s no secret that the technology landscape is always changing. New programming technologies and new languages are constantly emerging - but everything new also builds on the old. The iPhone or Android phone in your pocket is packed to the gills with cutting edge tech, but they’re also Unix-derivatives that can trace their origins back to the 1970s.
This constant influx of new ideas being built on top of old ones means that it’s quite common for developers to use several different technologies and languages over the course of their careers. A developer who started their career working on CRUD apps in Java may very well find herself writing iPhone apps in Swift today.
We can see these careers transitions by looking at developers who use Stack Overflow Jobs - and indeed in 2008 (the first full year after the iPhone was released), a large percent of the developers who switched to using Objective-C (Apple’s preferred language at the time) had previously been working in Java. And in recent years many Objective-C developers have transitioned to working in Swift (Apple’s new preferred language). A large number of people have taken the career path of our hypothetical developer above.
graphs c/o Julia Silge
You shouldn’t constrain yourself to hiring candidates with prior experience in your preferred programming language or tech stack - developers are perfectly capable of picking them up on the job.
Our own hiring practices provide additional empirical evidence - several of the developers we’ve hired at Stack Overflow had little or no prior experience with the Microsoft web stack, but they’ve always quickly got up to speed.