Hi Kasper, If what you're looking for is a more immediate solution, I can think of a couple of libraries which may do the trick:
1. Durian <https://github.com/diffplug/durian>'s TreeDef and TreeStream. Difficult to understand and use at first, but I believe it ticks a good number of boxes for you. 2. Guava 21 <https://github.com/google/guava/wiki/Release21>'s `TreeTraverser` with the library's new Java 8 support. For example, `Streams.stream(TreeTraverser.using(Node::getChildNodes).{preOrder|postOrder|breadthFirst}Traversal(rootNode));` Both of these solutions allow depth- and breadth-first traversals (the Guava solution allows both preOrder and postOrder depth traversals), but it's not clear to me if either of them allows you to set a maximum depth to traverse into. Hope this helps. Best regards, Jonathan On 20 January 2017 at 15:00, Remi Forax <fo...@univ-mlv.fr> wrote: > https://gist.github.com/forax/bca6877e019d134f87c4cb1e8efae9cd > > Rémi > > ----- Mail original ----- > > De: "Kasper Nielsen" <kaspe...@gmail.com> > > À: "core-libs-dev" <core-libs-dev@openjdk.java.net> > > Envoyé: Vendredi 20 Janvier 2017 11:03:41 > > Objet: Stream based API for tree like structures > > > Hi, > > > > Sorry if this is a bit off-topic, but I thought but I thought it might > have > > some general interest if Java ever got some proper tree/graph collection > > classes. > > > > Has anyone developed a stream based API that allows for tree based > travels. > > I'm mainly thinking about functionality for > > > > 1) > > Whether or not to do recursive traversal of all child nodes, only 1 level > > of child nodes, or just siblings > > > > 2) > > Order of traversal: depth/breadth first. > > > > I'm trying to avoid an explosion of methods such as > > streamSieblingsDepthOrderFirst. > > One thought I had was taking a var arg of options to stream and > > parallelStream such as: > > enum TreeStreamOptions { > > SIEBLINGS_ONLY, RECURSIVELY, DEPTH_FIRST, BREATH_FIRST; > > } > > Stream<T> stream(TreeStreamOptions... options) > > Stream<T> parallelStream(TreeStreamOptions... options) > > > > another one could be > > > > class TreeStreamOptions { > > TreeStreamOptions setDepthFirst(); > > TreeStreamOptions setBreathFirst(); > > TreeStreamOptions setDepth(); (0 sieblings only, Integer.MAX->infinity) > > } > > Stream<T> stream(TreeStreamOptions options) > > Stream<T> parallelStream(TreeStreamOptions options) > > > > While a visitor pattern would make sense for many use cases. I really > like > > the simplicity of just working with streams. > > > > Maybe someone has some thoughts on this. > > > > Best > > Kasper >
