What's outdated about Java/Swing? Java 8 is a fairly decent language, and Swing isn't bad. In fact the entire suite of JetBrains IDEs (WebStorm, PyCharm, IntelliJ, Android Studio, ReSharper, etc) have their UI implemented in Swing.
I suppose they could have used Kotlin, Scala, Haskell, or some other more language with a more advanced type system. But it would have been truly horrible had they written their back-end in an awful (dynamically typed) language like JavaScript or something.
I suppose they could have used Kotlin, Scala, Haskell, or some other more language with a more advanced type system. But it would have been truly horrible had they written their back-end in an awful (dynamically typed) language like JavaScript or something.