The Value of JSON Values A deep dive into JSON. by Join the DZone community and get the full member experience.Join For Free This article introduces json-values, a pure functional Java library to work with JSON. In this first article, we'll see some impressive recursive data structures to model essential concepts in software development like data validation, data generation, and parsers. The first and most important virtue of json-values is that JSON objects are immutable and implemented with persistent data structures, better known in FP jargon as values. As Pat Hellan said, immutability changes everything. It's a fact that, when possible, working with values leads to code with fewer bugs, is more readable, and is easier to maintain. Item 17 of Effective Java states that we must minimize mutability. Still, sometimes it's at the cost of losing performance because the copy-on-write approach is very inefficient for significant data structures. Here is where persistent data structures come into play.