This is a demo repository that shows my attempt at adapting Bazel's Digraph class to Guava's Graph interface.

Why? Because I'm interested in easy-to-use graph data structures in Java, and I thought this would be a fun exercise. 😄

• I made Digraph's Node class private and changed Digraph's API accordingly to make the class compatible with Guava's Graph interface.

• I expanded the original tests that the Bazel authors wrote for Digraph (which can be found in file DigraphTests.java in this repo) to assert that Digraph#getTopologicalOrder returns a series of nodes that satisfies the general definition of "topological ordering", rather than a specific sequence of nodes which is itself a valid topological ordering but not the only one.

  This means that one could, in theory, change the algorithm that Digraph#topologicalOrdering uses from reversed depth-first post order to e.g. Kahn's algorithm without having to change the test suite.

Install Java 8+, put it on your PATH, and then run the following commands through your terminal:

1. git clone https://github.com/jbduncan/bazel-digraph.git
2. cd bazel-digraph
3. ./gradlew check

Run ./gradlew build -x test. The library can then be found at build/libs/bazel-digraph-1.0-SNAPSHOT.jar.