Question

Can you please recommend a Java library for creating trees? I am looking for a library that will compute various paths between leaf nodes, report the number of leaf nodes the tree has, and other utility methods.

Answer 1

Try jgrapht. From the webpage:

JGraphT is a free Java graph library that provides mathematical graph-theory objects and algorithms. JGraphT supports various types of graphs including:

• directed and undirected graphs.
• graphs with weighted / unweighted / labeled or any user-defined edges.
• various edge multiplicity options, including: simple-graphs, multigraphs, pseudographs.
• unmodifiable graphs – allow modules to provide "read-only" access to internal graphs.
• listenable graphs – allow external listeners to track modification events.
• subgraphs graphs that are auto-updating subgraph views on other graphs.
• all compositions of above graphs.

Although powerful, JGraphT is designed to be simple and type-safe (via Java generics). For example, graph vertices can be of any objects. You can create graphs based on: Strings, URLs, XML documents, etc; you can even create graphs of graphs!

Other SO users report success with Jung. My careful 30 second review of their API suggests that you should start HERE.