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new 54e1edf 2026/05/13 02:12:53: Generated dev website from
groovy-website@10ed8c2
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commit 54e1edf1ed8b7ae385b9fdde84ae655241449d24
Author: jenkins <[email protected]>
AuthorDate: Wed May 13 02:12:53 2026 +0000
2026/05/13 02:12:53: Generated dev website from groovy-website@10ed8c2
---
blog/feed.atom | 13 +++-
blog/index.html | 4 +-
search/search-index.json | 4 +-
wiki/GEP-22.html | 180 ++++++++++++++++++++++++++++++++++++++++++++++-
4 files changed, 193 insertions(+), 8 deletions(-)
diff --git a/blog/feed.atom b/blog/feed.atom
index 719d44a..9086839 100644
--- a/blog/feed.atom
+++ b/blog/feed.atom
@@ -4,7 +4,18 @@
<link href="http://groovy.apache.org/blog"/>
<link href="http://groovy.apache.org/blog/feed.atom"; rel="self"/>
<id>http://groovy.apache.org/blog</id>
- <updated>2026-04-30T12:00:00Z</updated>
+ <updated>2026-05-07T12:00:00Z</updated>
+ <entry>
+ <id>http://groovy.apache.org/blog/groovy-mina-sshd</id>
+ <author>
+ <name>Paul King</name>
+ </author>
+ <title type="html">Fanning out across a Fleet with Apache MINA SSHD and
Groovy&trade; 6</title>
+ <link href="http://groovy.apache.org/blog/groovy-mina-sshd"/>
+ <updated>2026-05-07T12:00:00Z</updated>
+ <published>2026-05-07T12:00:00Z</published>
+ <summary type="html">A fleet of broker boxes over Apache MINA SSHD with
Groovy 6 parallel collections, Pool.virtual and ParallelScope -- replacing Part
1's stub feed.</summary>
+ </entry>
<entry>
<id>http://groovy.apache.org/blog/groovy-mina</id>
<author>
diff --git a/blog/index.html b/blog/index.html
index 28020ec..ca47dc4 100644
--- a/blog/index.html
+++ b/blog/index.html
@@ -63,7 +63,7 @@
</ul>
</div>
</div>
- </div><div id='content' class='page-1'><div
class='row'><div class='row-fluid'><div class='col-lg-3' id='blog-index'><ul
class='nav-sidebar list'><li class='active'><a
href='/blog/'>Blogs</a></li><li><a href='groovy-mina'>Streaming Servers with
Apache MINA and Groovy™ 6</a></li><li><a
href='groovy-async-await'>Async/await for Groovy™</a></li><li><a
href='groovy-null-checker'>Compile-time null safety for
Groovy™</a></li><li><a href='loop-invariant [...]
+ </div><div id='content' class='page-1'><div
class='row'><div class='row-fluid'><div class='col-lg-3' id='blog-index'><ul
class='nav-sidebar list'><li class='active'><a
href='/blog/'>Blogs</a></li><li><a href='groovy-mina-sshd'>Fanning out across a
Fleet with Apache MINA SSHD and Groovy™ 6</a></li><li><a
href='groovy-mina'>Streaming Servers with Apache MINA and Groovy™
6</a></li><li><a href='groovy-async-await'>Async/await for
Groovy™</a></li><li> [...]
<div class='row'>
<div class='colset-3-footer'>
<div class='col-1'>
@@ -107,7 +107,7 @@
colors: am5.ColorSet.new(root, {})
}));
wc.data.setAll([
- { category: "groovy", value: 90 }, { category: "asf", value: 2
}, { category: "apachecon", value: 3 }, { category: "communityovercode", value:
2 }, { category: "natural language processing", value: 2 }, { category: "nlp",
value: 1 }, { category: "nlpcraft", value: 1 }, { category: "combinations",
value: 1 }, { category: "permutations", value: 1 }, { category: "testing",
value: 2 }, { category: "junit", value: 2 }, { category: "spock", value: 2 }, {
category: "jqwik", valu [...]
+ { category: "groovy", value: 91 }, { category: "asf", value: 2
}, { category: "apachecon", value: 3 }, { category: "communityovercode", value:
2 }, { category: "natural language processing", value: 2 }, { category: "nlp",
value: 1 }, { category: "nlpcraft", value: 1 }, { category: "combinations",
value: 1 }, { category: "permutations", value: 1 }, { category: "testing",
value: 2 }, { category: "junit", value: 2 }, { category: "spock", value: 2 }, {
category: "jqwik", valu [...]
]);
wc.labels.template.setAll({
paddingTop: 5,
diff --git a/search/search-index.json b/search/search-index.json
index fa5d76f..7d0155c 100644
--- a/search/search-index.json
+++ b/search/search-index.json
@@ -709,7 +709,7 @@
{
"id": "blog/index.html",
"title": "The Apache Groovy programming language - Blogs",
- "content": "The Apache Groovy programming language - Blogs Socialize
Discuss on the mailing list Groovy on X Groovy on Bluesky Groovy on Mastodon
Groovy on LinkedIn Events and conferences Source code on GitHub Report issues
in Jira Stack Overflow questions Slack Community You are using an outdated
browser. Please upgrade your browser to improve your experience. Apache
Groovy™ Learn Documentation Download Support Contribute Ecosystem Blog
posts Socialize Blogs Streaming Serv [...]
+ "content": "The Apache Groovy programming language - Blogs Socialize
Discuss on the mailing list Groovy on X Groovy on Bluesky Groovy on Mastodon
Groovy on LinkedIn Events and conferences Source code on GitHub Report issues
in Jira Stack Overflow questions Slack Community You are using an outdated
browser. Please upgrade your browser to improve your experience. Apache
Groovy™ Learn Documentation Download Support Contribute Ecosystem Blog
posts Socialize Blogs Fanning out ac [...]
"url": "blog/index.html",
"site": "dev"
},
@@ -793,7 +793,7 @@
{
"id": "wiki/GEP-22.html",
"title": "The Apache Groovy programming language - Developer docs -
GEP-22",
- "content": "The Apache Groovy programming language - Developer docs -
GEP-22 Socialize Discuss on the mailing list Groovy on X Groovy on Bluesky
Groovy on Mastodon Groovy on LinkedIn Events and conferences Source code on
GitHub Report issues in Jira Stack Overflow questions Slack Community You are
using an outdated browser. Please upgrade your browser to improve your
experience. Apache Groovy™ Learn Documentation Download Support
Contribute Ecosystem Blog posts Socialize GE [...]
+ "content": "The Apache Groovy programming language - Developer docs -
GEP-22 Socialize Discuss on the mailing list Groovy on X Groovy on Bluesky
Groovy on Mastodon Groovy on LinkedIn Events and conferences Source code on
GitHub Report issues in Jira Stack Overflow questions Slack Community You are
using an outdated browser. Please upgrade your browser to improve your
experience. Apache Groovy™ Learn Documentation Download Support
Contribute Ecosystem Blog posts Socialize GE [...]
"url": "wiki/GEP-22.html",
"site": "dev"
},
diff --git a/wiki/GEP-22.html b/wiki/GEP-22.html
index a873990..e1fe7e1 100644
--- a/wiki/GEP-22.html
+++ b/wiki/GEP-22.html
@@ -63,7 +63,7 @@
</ul>
</div>
</div>
- </div><div id='content' class='page-1'><div
class='row'><div class='row-fluid'><div class='col-lg-3'><ul
class='nav-sidebar'><li><a href='geps.html'>GEP index</a></li><li
class='active'><a href='#doc'>GEP-22</a></li><li><a href='#_abstract_traits'
class='anchor-link'>Abstract: Traits</a></li><li><a href='#_specification'
class='anchor-link'>Specification</a></li><li><a
href='#_cross_version_evolution' class='anchor-link'>Cross-version
evolution</a></li><li><a href [...]
+ </div><div id='content' class='page-1'><div
class='row'><div class='row-fluid'><div class='col-lg-3'><ul
class='nav-sidebar'><li><a href='geps.html'>GEP index</a></li><li
class='active'><a href='#doc'>GEP-22</a></li><li><a href='#_abstract_traits'
class='anchor-link'>Abstract: Traits</a></li><li><a href='#_specification'
class='anchor-link'>Specification</a></li><li><a
href='#_comparison_with_related_constructs' class='anchor-link'>Comparison with
related construc [...]
<div class="sectionbody">
<div class="sidebarblock">
<div class="content">
@@ -91,7 +91,7 @@
<strong>Version</strong>
</td>
<td class="hdlist2">
-<p>1</p>
+<p>2</p>
</td>
</tr>
<tr>
@@ -139,7 +139,7 @@
<strong>Last modification</strong>
</td>
<td class="hdlist2">
-<p>2026-05-06</p>
+<p>2026-05-11</p>
</td>
</tr>
</table>
@@ -226,6 +226,12 @@ Champeau put it when introducing them: traits
<strong>extend the benefit of
interfaces to concrete classes</strong> without producing inheritance pyramids,
allowing new APIs to be layered onto existing classes without modification.</p>
</div>
+<div class="paragraph">
+<p>A side-by-side comparison with Scala traits, Kotlin interfaces, and Java
+default methods is given in
+<a href="#_comparison_with_related_constructs">Comparison with related
constructs</a>
+below.</p>
+</div>
</div>
</div>
</div>
@@ -577,6 +583,167 @@ direct field reference.</p>
</div>
</div>
<div class="sect1">
+<h2 id="_comparison_with_related_constructs">Comparison with related
constructs</h2>
+<div class="sectionbody">
+<div class="paragraph">
+<p>Groovy traits occupy a design space shared with Scala traits, Kotlin
+interfaces (including their companion-object machinery), and Java default
+methods. Each construct trades expressiveness for simplicity in its own
+way. The table below cross-references the load-bearing features of Groovy
+traits against the closest analogue in each language.</p>
+</div>
+<table class="tableblock frame-all grid-all stretch">
+<colgroup>
+<col style="width: 14.2857%;">
+<col style="width: 21.4285%;">
+<col style="width: 21.4285%;">
+<col style="width: 21.4285%;">
+<col style="width: 21.4288%;">
+</colgroup>
+<thead>
+<tr>
+<th class="tableblock halign-left valign-top">Feature</th>
+<th class="tableblock halign-left valign-top">Groovy <code>trait</code></th>
+<th class="tableblock halign-left valign-top">Scala <code>trait</code></th>
+<th class="tableblock halign-left valign-top">Kotlin
<code>interface</code></th>
+<th class="tableblock halign-left valign-top">Java <code>interface</code>
(default methods)</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Instance
state (fields)</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Yes. Woven
into the implementing class via a field-helper class with name-mangled
identifiers; no diamond-of-state risk.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Yes.
First-class <code>val</code>/<code>var</code> members; conflicts resolved by
linearization.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">No backing
fields. Only abstract or computed properties are permitted.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">No state
of any kind.</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Static
methods</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Yes
(incubating). Each implementing class receives its own copy; not exposed on the
generated interface. See <a href="#_static_members">Static members</a>.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Indirect,
via a companion <code>object</code>. Static-like state lives on a singleton,
not per implementer.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Indirect,
via a <code>companion object</code> declared inside the interface. Members are
instance members of the companion; <code>@JvmStatic</code> promotes them to
true JVM statics.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Yes (since
Java 8). Resolved against the declaring interface; <strong>not</strong>
inherited by sub-interfaces or implementing classes.</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Static
state (fields)</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Yes
(incubating). Stored in a per-implementer static-field-helper class.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Via the
companion <code>object</code> — one copy per trait.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Via the
companion <code>object</code> — one copy per interface.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Yes — one
copy per interface.</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p
class="tableblock">Constructors / parameters</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Not
permitted.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Scala 3
supports trait parameters (e.g. <code>trait T(val name: String)</code>); Scala
2 does not.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Not
permitted.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Not
permitted.</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Method
visibility</p></td>
+<td class="tableblock halign-left valign-top"><p
class="tableblock"><code>public</code> and <code>private</code> only (also
<code>private static</code>); <code>protected</code> and package-private are
rejected.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Full
range, including <code>protected</code> and qualified
<code>private[pkg]</code>.</p></td>
+<td class="tableblock halign-left valign-top"><p
class="tableblock"><code>public</code> and <code>private</code>.</p></td>
+<td class="tableblock halign-left valign-top"><p
class="tableblock"><code>public</code>, <code>public static</code>, and
<code>private</code> (Java 9+).</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p
class="tableblock">Inherited-method conflict resolution</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Last-wins
by <code>implements</code>-clause order; override by re-declaring in the
implementing class or via <code>T.super.m()</code>.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">C3
linearization — deterministic right-to-left walk of the inheritance graph;
<code>super[T].m()</code> selects a specific ancestor.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Diamond is
a <strong>compile error</strong>. The implementing class must resolve it
explicitly via <code>super<T>.foo()</code>.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Diamond is
a <strong>compile error</strong>. The implementing class must resolve it
explicitly via <code>T.super.foo()</code>.</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Stackable
<code>super</code></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Yes.
Unqualified <code>super.m()</code> walks the trait chain in
<code>implements</code> order; <code>T.super.m()</code> jumps directly to trait
<code>T</code>.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Yes.
<code>super.m()</code> follows the linearization order;
<code>super[T].m()</code> is the explicit form.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">No.
<code>super</code> requires a type qualifier wherever it is ambiguous; there is
no walked chain.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">No.
<code>T.super.m()</code> is the only stack form; there is no chain to
walk.</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p
class="tableblock">Self-types</p></td>
+<td class="tableblock halign-left valign-top"><p
class="tableblock"><code>@groovy.transform.SelfType(Foo.class)</code>
annotation; statically checked.</p></td>
+<td class="tableblock halign-left valign-top"><p
class="tableblock">First-class syntax <code>self: Foo =></code> inside the
trait body.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Not
supported; expressed via bounded generics where unavoidable.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Not
supported.</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Runtime
application to existing instances</p></td>
+<td class="tableblock halign-left valign-top"><p
class="tableblock"><code>subject as Trait</code> and
<code>subject.withTraits(A, B)</code> produce a new proxy that implements the
trait(s) and delegates to the original.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Only at
construction: <code>new C with TraitA with TraitB</code>. No way to attach a
trait to an existing instance.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Not
supported.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Not
supported.</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">SAM
coercion from a closure / lambda</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Yes, for a
single-abstract-method trait. See GEP-12.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Yes, via
SAM types and function literals.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Yes, for
<code>fun interface</code> declarations.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Yes, for
any functional interface.</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p
class="tableblock">Java-callable view of the construct</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">A plain
interface — <strong>no</strong> default methods. State and behaviour live in
helper classes.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">A JVM
interface containing <code>default</code> methods (since Scala 2.12).</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">A JVM
interface; default-method generation is controlled by
<code>-Xjvm-default</code>.</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">A JVM
interface natively.</p></td>
+</tr>
+</tbody>
+</table>
+<div class="paragraph">
+<p>A few qualitative observations follow from the table:</p>
+</div>
+<div class="ulist">
+<ul>
+<li>
+<p><strong>State is the dividing line.</strong> Only Groovy and Scala give
traits true
+instance state; Kotlin and Java explicitly avoid it. Groovy’s
+field-helper indirection is the price paid for keeping the Java-visible
+view of a trait as a <strong>plain</strong> interface (no default methods, no
surprise
+multiple-inheritance behaviour for Java consumers).</p>
+</li>
+<li>
+<p><strong>Conflict-resolution philosophies differ.</strong> Groovy chooses a
+deterministic <strong>default</strong> (last-wins) so that conflicts compile
without
+intervention. Scala chooses a deterministic <strong>algorithm</strong>
(linearization)
+that the developer is expected to internalise. Kotlin and Java refuse to
+choose and require the developer to resolve every conflict explicitly.
+Each position is internally consistent; Groovy’s optimises for
+ergonomics, Scala’s for expressiveness, and Java/Kotlin’s for
safety
+against accidental composition.</p>
+</li>
+<li>
+<p><strong>Stackable <code>super</code> is a Groovy/Scala feature.</strong> It
is what enables the
+mixin-style decorator composition that motivates traits in the first
+place. Kotlin and Java interfaces cannot express the same pattern
+without auxiliary delegation.</p>
+</li>
+<li>
+<p><strong>Static members are the rough edge in every language.</strong> Java
and Kotlin
+treat them as per-interface (no inheritance, no overriding). Scala
+routes them through a separate companion object whose members live on
+a singleton rather than per implementer. Groovy is the only one of the
+four that gives each implementing class its own copy of static members;
+this is what enables patterns such as overriding static defaults from
+the implementing class (e.g. Grails' <code>Validateable</code>), but is also
why
+static-method dispatch remains an open design point — see
+<a href="#_non_goals_and_potential_future_extensions">Non-goals</a>.</p>
+</li>
+<li>
+<p><strong>Runtime trait application</strong> (the <code>as</code> /
<code>withTraits</code> form) is unique to
+Groovy. None of the other three constructs offers a way to attach a
+trait to an <strong>existing</strong> instance at runtime.</p>
+</li>
+<li>
+<p><strong>Self-types</strong> are first-class in Scala, an annotation in
Groovy, and
+absent from Kotlin and Java. The Groovy and Scala forms enable
+statically checked traits whose bodies depend on members supplied by
+the implementing class without resorting to defensive casts.</p>
+</li>
+</ul>
+</div>
+</div>
+</div>
+<div class="sect1">
<h2 id="_cross_version_evolution">Cross-version evolution</h2>
<div class="sectionbody">
<table class="tableblock frame-all grid-all stretch">
@@ -815,6 +982,13 @@ trait field reference transform restructure.</p>
trait semantics as shipped in 2.3.0 and refined through 5.0, the
four-class bytecode model, and the cross-version evolution table.</p>
</div>
+<div class="paragraph">
+<p>2 (2026-05-11) Added <em>Comparison with related constructs</em> section
+contrasting Groovy traits with Scala traits, Kotlin interfaces, and
+Java default methods across state, conflict resolution, stackable
+<code>super</code>, static members, self-types, runtime application, and the
+Java-callable view.</p>
+</div>
</div>
</div></div></div></div></div><footer id='footer'>
<div class='row'>
