The most productive people may program in mainstream languages like Java, but their programming is informed by exposure to a broader variety of languages than j

The most productive people may program in mainstream languages like Java, but their programming is informed by exposure to a broader variety of languages than just the mainstream ones. To stick with Java as the example, Java was designed with a set of affordances for managing mutability, complex inheritance relationships, and objects with rich behavior, and the coding norms and "wisdom" surrounding Java in the early years was based on that. Appreciation for immutability, value objects, and transformation rather than mutation came from outside of Java. That's my experience and the experience of the people I've worked with: our understanding of the value of immutability and dumb data came from working in languages that demanded or at least strongly suggested it and had elegant affordances for it. If we worked exclusively in Java, we would have been much less likely to realize the value of an approach that seemed alien and awkward in our language of choice. (Eventually, due to popular demand, better language support was tacked onto Java, but I'm talking about 10+ years ago.) Every programmer should at least dabble in other languages and try to absorb the good big ideas from them, even if they ultimately put these ideas to work in "mainstream" languages.