In my previous articles about functional programming, I’ve shown how to incorporate a more functional style into our Java code. But I’ve omitted a crucial topic: how to deal with exceptions.

Almost every developer knows the phrase “premature optimization is the root of all evil”, coined by Donald Knuth in 1974. But how are we supposed to know what is worthy of being optimized?

Every time we create a new data structure, we have to decide which data types to use. Usually, the decision is simple: text most likely will become a String, non-floating-point numbers will be int, and so forth. Most of the time, these almost subconsciously-made decisions will suffice. But to design future-proof data structures, we have to think about choosing the correct data type a little more.

Exception handling is a mechanism used to handle disruptive, abnormal conditions to the control flow of our programs. The concept can be traced back to the origins of Lisp and is used in many different programming languages today.

Martin Fowler, who coined the term Fluent Interfaces 15 years ago, famously wrote in his book Refactoring: Improving the Design of Existing Code: “Any fool can write code that a computer can understand. Good programmers write code that humans can understand.”