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new b3e30a8 add groupByMany blog post (minor tweaks)
b3e30a8 is described below
commit b3e30a86a1779b6a5c4ce641f61e1b4efd56e4de
Author: Paul King <[email protected]>
AuthorDate: Tue Dec 2 11:53:36 2025 +1000
add groupByMany blog post (minor tweaks)
---
site/src/site/blog/fruity-eclipse-grouping.adoc | 41 ++++++++++++++++++++++---
1 file changed, 36 insertions(+), 5 deletions(-)
diff --git a/site/src/site/blog/fruity-eclipse-grouping.adoc
b/site/src/site/blog/fruity-eclipse-grouping.adoc
index 76236e2..5712c5d 100644
--- a/site/src/site/blog/fruity-eclipse-grouping.adoc
+++ b/site/src/site/blog/fruity-eclipse-grouping.adoc
@@ -30,14 +30,22 @@ assert Fruit.ALL.groupBy(Fruit::getColor) ==
----
We have a collection of fruit and we have colors.
-The fruit is an enum. The colors are `java.awt.Color` values.
-We won't show the details of those but see the previous blog posts or the
-associated GitHub repo if you want all the details.
+See the previous blog posts or the
+associated GitHub repo if you want all the details,
+but here's a brief summary of our domain:
+
+* each fruit is an enum having a `getColor` method to return its color
+* there is also an `of` factory method for creating a `Fruit`,
+e.g. `APPLE`, from its emoji, e.g. `'🍎'`
+* the colors are `java.awt.Color` values
+* ALL returns the `values()` as an `ImmutableList`
+* Eclipse Collections multimaps are the result type of `groupBy`
As originally presented,
there is a one-to-many relationship between fruit and their color.
A fruit has one color, but there can be many fruit of a particular color.
-That's what `groupBy` allows us to explore.
+That's what `groupBy` allows us to explore. It captures the
+color relationship in the returned multimap.
In this post, we want to explore grouping in the context of many-to-many
relationships.
@@ -45,7 +53,7 @@ As an example, suppose now that rather than just coming in
one _typical_ color,
in our case the predominant color of the supplied emoji, that multiple colors
might be possible for
any given fruit: red and green apples, a green unripe banana, and so forth.
So, let's expand the previous example so that rather than calling `getColor`
to find _the_ color,
-we'll call `getColors` to find a list of potential colors.
+we'll call `getColors` to find the list of potential colors.
We'll do that first using Eclipse Collections and then look at various
possibilities
for JDK collections when using Groovy.
@@ -221,6 +229,29 @@ assert availability.groupByMany() == [
[Sorry U.S. folks, _Autumn_ has the same number of letters as the other season
names
and makes the last map look prettier - _Fall_ just didn't cut it this time!]
+This Map variant is the equivalent of Eclipse Collections `flip` method on
multimaps
+as this example shows:
+
+[source,groovy]
+----
+var fruitColors = Multimaps.mutable.set.empty()
+fruitColors.put('red', '🍒')
+fruitColors.put('red', '🍎')
+fruitColors.put('green', '🍎')
+fruitColors.put('yellow', '🍌')
+fruitColors.put('green', '🍌')
+fruitColors.put('green', '🥑')
+println fruitColors
+println fruitColors.flip()
+----
+
+Which has this output:
+
+----
+{red=[🍒, 🍎], green=[🍌, 🥑, 🍎], yellow=[🍌]}
+{🍒=[red], 🍌=[green, yellow], 🥑=[green], 🍎=[red, green]}
+----
+
== Further information
* Repo with example code:
https://github.com/paulk-asert/fruity-eclipse-collections
