Small experiment to see how well Kotlin works with JavaFX, which turned out really elegantly. The apply { } block function is perfect for building UI controls in code, and Kotlin's lambdas are even more elegant than Java 8's thanks to the implicit it parameter for SAM functions.
The app itself just watches a text field (that rejects non-decimal inputs), rounds the input with BigDecimal#round(), and displays the result. The window is draggable by its background due to its hidden OS frame.
