support yaml, making it easier to contribute

Author: hallvard

content/collections/collectors-teeing.json

@@ -0,0 +1,49 @@
+id: 26
+slug: collectors-teeing
+title: Collectors.teeing()
+category: collections
+difficulty: intermediate
+jdkVersion: "12"
+oldLabel: Java 8
+modernLabel: Java 12+
+oldApproach: Two Passes
+modernApproach: teeing()
+oldCode: |
+  // python
+  long count = items.stream().count();
+  double sum = items.stream()
+      .mapToDouble(Item::price)
+      .sum();
+  var result = new Stats(count, sum);
+modernCode: |
+  var result = items.stream().collect(
+      Collectors.teeing(
+          Collectors.counting(),
+          Collectors.summingDouble(Item::price),
+          Stats::new
+      )
+  );
+summary: Compute two aggregations in a single stream pass.
+explanation: Collectors.teeing() sends each element to two downstream collectors and merges the results. This avoids streaming the data twice or using a mutable accumulator.
+whyModernWins:
+  - icon: ⚡
+    title: Single pass
+    desc: Process the stream once instead of twice.
+  - icon: 🧩
+    title: Composable
+    desc: Combine any two collectors with a merger function.
+  - icon: 🔒
+    title: Immutable result
+    desc: Merge into a record or value object directly.
+support:
+  state: available
+  description: Widely available since JDK 12 (March 2019)
+prev: collections/sequenced-collections
+next: collections/stream-toarray-typed
+related:
+  - collections/copying-collections-immutably
+  - collections/unmodifiable-collectors
+  - collections/stream-toarray-typed
+docs:
+  - title: Collectors.teeing()
+    href: https://docs.oracle.com/en/java/javase/25/docs/api/java.base/java/util/stream/Collectors.html#teeing(java.util.stream.Collector,java.util.stream.Collector,java.util.function.BiFunction)

content/collections/collectors-teeing.yaml

@@ -1,10 +1,12 @@
 ///usr/bin/env jbang "$0" "$@" ; exit $?
 //JAVA 25
 //DEPS com.fasterxml.jackson.core:jackson-databind:2.18.3
+//DEPS com.fasterxml.jackson.dataformat:jackson-dataformat-yaml:2.18.3
 
 import module java.base;
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
 
 /**
  * Generate HTML detail pages from JSON snippet files and slug-template.html.
@@ -14,7 +16,13 @@
 static final String CONTENT_DIR = "content";
 static final String SITE_DIR = "site";
 static final Pattern TOKEN = Pattern.compile("\\{\\{(\\w+)}}");
-static final ObjectMapper MAPPER = new ObjectMapper();
+static final ObjectMapper JSON_MAPPER = new ObjectMapper();
+static final ObjectMapper YAML_MAPPER = new ObjectMapper(new YAMLFactory());
+static final Map<String, ObjectMapper> MAPPERS = Map.of(
+    "json", JSON_MAPPER,
+    "yaml", YAML_MAPPER,
+    "yml", YAML_MAPPER
+);
 
 static final String CATEGORIES_FILE = "html-generators/categories.properties";
 static final SequencedMap<String, String> CATEGORY_DISPLAY = loadCategoryDisplay();
@@ -100,7 +108,7 @@ void main() throws IOException {
     // Rebuild data/snippets.json
     var snippetsList = allSnippets.values().stream()
             .map(s -> {
-                Map<String, Object> map = MAPPER.convertValue(s.node(), new TypeReference<LinkedHashMap<String, Object>>() {});
+                Map<String, Object> map = JSON_MAPPER.convertValue(s.node(), new TypeReference<LinkedHashMap<String, Object>>() {});
                 EXCLUDED_KEYS.forEach(map::remove);
                 return map;
             })
@@ -127,14 +135,16 @@ SequencedMap<String, Snippet> loadAllSnippets() throws IOException {
     for (var cat : CATEGORY_DISPLAY.sequencedKeySet()) {
         var catDir = Path.of(CONTENT_DIR, cat);
         if (!Files.isDirectory(catDir)) continue;
-        try (var stream = Files.newDirectoryStream(catDir, "*.json")) {
-            var sorted = new ArrayList<Path>();
-            stream.forEach(sorted::add);
-            sorted.sort(Path::compareTo);
-            for (var path : sorted) {
-                var snippet = new Snippet(MAPPER.readTree(path.toFile()));
-                snippets.put(snippet.key(), snippet);
-            }
+        for (var ext : MAPPERS.keySet()) {
+          try (var stream = Files.newDirectoryStream(catDir, "*." + ext)) {
+              var sorted = new ArrayList<Path>();
+              stream.forEach(sorted::add);
+              sorted.sort(Path::compareTo);
+              for (var path : sorted) {
+                  var snippet = new Snippet(MAPPERS.get(ext).readTree(path.toFile()));
+                  snippets.put(snippet.key(), snippet);
+              }
+          }
         }
     }
     return snippets;
@@ -145,7 +155,7 @@ String escape(String text) {
 }
 
 String jsonEscape(String text) throws IOException {
-    var quoted = MAPPER.writeValueAsString(text);
+    var quoted = JSON_MAPPER.writeValueAsString(text);
     var inner = quoted.substring(1, quoted.length() - 1);
     var sb = new StringBuilder(inner.length());
     for (int i = 0; i < inner.length(); i++) {

html-generators/generate.java

@@ -2,6 +2,7 @@
 """Generate HTML detail pages from JSON snippet files and slug-template.html."""
 
 import json
+import yaml
 import glob
 import os
 import html
@@ -73,10 +74,16 @@ def load_all_snippets():
     snippets = {}
     json_files = []
     for cat in CATEGORY_DISPLAY:
-        json_files.extend(sorted(glob.glob(f"{CONTENT_DIR}/{cat}/*.json")))
+        json_files.extend(glob.glob(f"{CONTENT_DIR}/{cat}/*.json"))
+        json_files.extend(glob.glob(f"{CONTENT_DIR}/{cat}/*.yaml"))
+        json_files.extend(glob.glob(f"{CONTENT_DIR}/{cat}/*.yml"))
+    json_files.sort()
     for path in json_files:
         with open(path) as f:
-            data = json.load(f)
+            if path.endswith(".yaml") or path.endswith(".yml"):
+                data = yaml.safe_load(f)
+            else:
+                data = json.load(f)
         key = f"{data['category']}/{data['slug']}"
         data["_path"] = key
         snippets[key] = data