Add select methods returning element streams

src/main/java/org/jsoup/nodes/Element.java

@@ -486,6 +486,41 @@ public Elements select(Evaluator evaluator) {
         return Selector.select(evaluator, this);
     }
 
+    /**
+     * Find elements that match the {@link Selector} CSS query, with this element as the starting context. Matched elements
+     * may include this element, or any of its children.
+     * <p>This method is generally more powerful to use than the DOM-type {@code getElementBy*} methods, because
+     * multiple filters can be combined, e.g.:</p>
+     * <ul>
+     * <li>{@code el.selectStream("a[href]")} - finds links ({@code a} tags with {@code href} attributes)
+     * <li>{@code el.selectStream("a[href*=example.com]")} - finds links pointing to example.com (loosely)
+     * </ul>
+     * <p>See the query syntax documentation in {@link org.jsoup.select.Selector}.</p>
+     * <p>Also known as {@code querySelectorAll()} in the Web DOM.</p>
+     *
+     * @param cssQuery a {@link Selector} CSS-like query
+     * @return a {@link Stream} containing elements that match the query (empty if none match)
+     * @see Selector selector query syntax
+     * @see QueryParser#parse(String)
+     * @throws Selector.SelectorParseException (unchecked) on an invalid CSS query.
+     * @since 1.18.1
+     */
+    public Stream<Element> selectStream(String cssQuery) {
+        return Selector.selectStream(cssQuery, this);
+    }
+
+    /**
+     * Find elements that match the supplied Evaluator. This has the same functionality as {@link #select(String)}, but
+     * may be useful if you are running the same query many times (on many documents) and want to save the overhead of
+     * repeatedly parsing the CSS query.
+     * @param evaluator an element evaluator
+     * @return a {@link Stream} containing elements that match the query (empty if none match)
+     * @since 1.18.1
+     */
+    public Stream<Element> selectStream(Evaluator evaluator) {
+        return Selector.selectStream(evaluator, this);
+    }
+
     /**
      * Find the first Element that matches the {@link Selector} CSS query, with this element as the starting context.
      * <p>This is effectively the same as calling {@code element.select(query).first()}, but is more efficient as query
@@ -1126,11 +1161,7 @@ public Elements getElementsByTag(String tagName) {
     public @Nullable Element getElementById(String id) {
         Validate.notEmpty(id);
 
-        Elements elements = Collector.collect(new Evaluator.Id(id), this);
-        if (elements.size() > 0)
-            return elements.get(0);
-        else
-            return null;
+        return selectStream(new Evaluator.Id(id)).findFirst().orElse(null);
     }
 
     /**

src/main/java/org/jsoup/select/Collector.java

@@ -3,8 +3,8 @@
 import org.jsoup.nodes.Element;
 import org.jspecify.annotations.Nullable;
 
-import java.util.Optional;
 import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 /**
  * Collects a list of elements that match the supplied criteria.
@@ -21,12 +21,22 @@ private Collector() {}
      @param root root of tree to descend
      @return list of matches; empty if none
      */
-    public static Elements collect (Evaluator eval, Element root) {
-        eval.reset();
+    public static Elements collect(Evaluator eval, Element root) {
+        return stream(eval, root).collect(Collectors.toCollection(Elements::new));
+    }
+
+    /**
+     * Obtain a stream of elements by visiting root and every descendant of root and testing it
+     * against the evaluator.
+     * @param evaluator Evaluator to test elements against
+     * @param root root of tree to descend
+     * @return A {@link Stream} of matches
+     */
+    public static Stream<Element> stream(Evaluator evaluator, Element root) {
+        evaluator.reset();
 
         return root.stream()
-            .filter(eval.asPredicate(root))
-            .collect(Collectors.toCollection(Elements::new));
+            .filter(evaluator.asPredicate(root));
     }
 
     /**
@@ -37,9 +47,6 @@ public static Elements collect (Evaluator eval, Element root) {
      @return the first match; {@code null} if none
      */
     public static @Nullable Element findFirst(Evaluator eval, Element root) {
-        eval.reset();
-
-        Optional<Element> first = root.stream().filter(eval.asPredicate(root)).findFirst();
-        return first.orElse(null);
+        return stream(eval, root).findFirst().orElse(null);
     }
 }

src/main/java/org/jsoup/select/Selector.java

@@ -6,6 +6,7 @@
 
 import java.util.Collection;
 import java.util.IdentityHashMap;
+import java.util.stream.Stream;
 
 /**
  * CSS-like element selector, that finds elements matching a query.
@@ -114,6 +115,32 @@ public static Elements select(Evaluator evaluator, Element root) {
         return Collector.collect(evaluator, root);
     }
 
+    /**
+     * Find elements matching selector.
+     *
+     * @param query CSS selector
+     * @param root  root element to descend into
+     * @return matching elements, empty if none
+     * @throws Selector.SelectorParseException (unchecked) on an invalid CSS query.
+     */
+    public static Stream<Element> selectStream(String query, Element root) {
+        Validate.notEmpty(query);
+        return selectStream(QueryParser.parse(query), root);
+    }
+
+    /**
+     * Find elements matching selector.
+     *
+     * @param evaluator CSS selector
+     * @param root root element to descend into
+     * @return matching elements, empty if none
+     */
+    public static Stream<Element> selectStream(Evaluator evaluator, Element root) {
+        Validate.notNull(evaluator);
+        Validate.notNull(root);
+        return Collector.stream(evaluator, root);
+    }
+
     /**
      * Find elements matching selector.
      *

src/test/java/org/jsoup/nodes/ElementTest.java

@@ -2924,4 +2924,15 @@ void prettySerializationRoundTrips(Document.OutputSettings settings) {
         assertEquals("<p CLASS=\"YES\">One</p>", p.outerHtml());
         assertEquals("CLASS=\"YES\"", attr.html());
     }
+
+    @Test void testSelectStream() {
+        Document doc = Jsoup.parse("<div>Hello world</div>");
+        Element div = doc.select("div").stream().findFirst().orElse(null);
+
+        assertEquals("Hello world", div.text());
+
+        div = doc.selectStream("div").findFirst().orElse(null);
+
+        assertEquals("Hello world", div.text());
+    }
 }