Streems
Read me first
This project is licensed under the Apache Software License, version 2. See the LICENSE file at the root of the project for more details.
This project requires Java 8.
The current version is 0.2.0:
dependencies {
compile(group: "com.github.javachat", name: "streems", version: "0.1.0");
}
Another package exists which provides a way to reuse a TreeTraverer
from Guava
(see below):
dependencies {
compile(group: "com.github.javachat", name: "streems-guava", version: "0.1.0");
}
What this is
This library provides a
Stream
interface over n-ary trees.
The idea was inspired by Guava's
TreeTraverser
.
Since Guava is aimed at Java 7 or less, its traversal methods return instances
of
Iterable
s,
not Stream
s. This package provides such a functionality.
The different traversals of an n-ary tree
An example is provided by the javadoc of TreeTraverser
; we will reproduce it
here:
For example, the tree
h
/ | \
/ e \
d g
/|\ |
/ | \ f
a b c
can be iterated over in preorder (hdabcegf), postorder (abcdefgh), or
breadth-first order (hdegabcf).
Usage
You provide a class which gives access to its immediate children, in order, using either of:
- a
Stream
, - an
Iterator
, - an
Iterable
, - or an array.
You can then use this API to traverse instances of the class as an n-ary tree in any order: preorder, postorder or breadth first.
For instance:
final Stream<MyNode> stream
= Streems.traverse(myNode, MyNode::children, Traversal.PREORDER);
Notes about the returned Streams...
The underlying
Spliterator
will always have the same characteristics:
ORDERED
and
NONNULL
:
ORDERED
is obvious... After all, you choose the traversal order and you expect nodes to be returned in that order;NONNULL
because it is a requirement (you cannot attempt to get any children from a null node).