Earlier quoted context omitted.
There is already MacRuby and RubyMotion. They tried using Java years ago. It failed. Developers didn't like it. Existing stuff simply doesn't mix that well with Cocoa and that style of programming. That is why something like Swift was needed. I really don't get why you can bring up languages such as Rust and Go, and complain about Apple's special snowflake approach. Suddenly Apple is doing something developers have b…
Suddenly Apple is doing something developers have been demanding from them for years and something lots of other companies like Google, Mozila and Microsoft has already done. And yet they've decided to do it again, with yet another incompatible language! Joy of joys! (And as for Java, it was my understanding that Apple had hobbled it by refusing to release updates on a timely basis.)
That's a different, later issue.
Early on in the life of OS X, Apple offered a Java interface to the Cocoa class frameworks. In theory, you could write OS X applications using Java, calling into the Apple frameworks instead of using Swing or whatever Java frameworks.
This wasn't all that well supported, didn't perform well, and wasn't popular.