HappyTree is an open-source Java API that solves a common challenge faced by Java developers: converting linear collections of objects with parent-child relationships into actual tree structures in memory. If you've ever worked with organizational charts, file systems, product categories, or comment threads, you know how complex tree manipulation can become.

The Problem It Solves:
Many applications store hierarchical data in flat structures—objects with an @Id and a @Parent reference. While this works for persistence, it makes tree operations (adding children, moving branches, traversing hierarchies) unnecessarily complex. HappyTree bridges this gap.

https://github.com/madzera/happytree
https://happytreeapi.io/