This is a basic functional calculator built in Java using the swing library/framework. While it handles all of the basics fairly well, it is not meant to be accurate for very large or very small numbers. The focus of this project was to practice using swing to acheive a functional program. A production ready calculator would need to be built with the BigDecimal class in order to handle arbitrarily large or small numbers with whatever desired precision.
Given how dated Swing is, I'm not entirely sure if it's worth adding features. Perhaps a JavaFX version would make more sense...