Optimize HttpHeaders.getAcceptLanguageAsLocales

The HttpHeaders.getAcceptLanguageAsLocales was incurring overhead from
using a Stream, as well as calling the fairly expensive
Locale.getDisplayName method.

Switch to using an ArrayList, and skipping over wildcard ranges to avoid
needing to check the display name.

Closes gh-32318

Author: kilink

spring-web/src/main/java/org/springframework/http/HttpHeaders.java

@@ -527,10 +527,14 @@ public List<Locale> getAcceptLanguageAsLocales() {
 		if (ranges.isEmpty()) {
 			return Collections.emptyList();
 		}
-		return ranges.stream()
-				.map(range -> Locale.forLanguageTag(range.getRange()))
-				.filter(locale -> StringUtils.hasText(locale.getDisplayName()))
-				.toList();
+
+		List<Locale> locales = new ArrayList<>(ranges.size());
+		for (Locale.LanguageRange range : ranges) {
+			if (!range.getRange().startsWith("*")) {
+				locales.add(Locale.forLanguageTag(range.getRange()));
+			}
+		}
+		return locales;
 	}
 
 	/**

spring-web/src/test/java/org/springframework/http/HttpHeadersTests.java

@@ -471,22 +471,27 @@ void accessControlRequestMethod() {
 
 	@Test
 	void acceptLanguage() {
-		String headerValue = "fr-ch, fr;q=0.9, en-*;q=0.8, de;q=0.7, *;q=0.5";
+		String headerValue = "fr-ch, fr;q=0.9, en-*;q=0.8, de;q=0.7, *-us;q=0.6, *;q=0.5";
 		headers.setAcceptLanguage(Locale.LanguageRange.parse(headerValue));
 		assertThat(headers.getFirst(HttpHeaders.ACCEPT_LANGUAGE)).isEqualTo(headerValue);
 
-		List<Locale.LanguageRange> expectedRanges = Arrays.asList(
+		List<Locale.LanguageRange> expectedRanges = List.of(
 				new Locale.LanguageRange("fr-ch"),
 				new Locale.LanguageRange("fr", 0.9),
 				new Locale.LanguageRange("en-*", 0.8),
 				new Locale.LanguageRange("de", 0.7),
+				new Locale.LanguageRange("*-us", 0.6),
 				new Locale.LanguageRange("*", 0.5)
 		);
 		assertThat(headers.getAcceptLanguage()).isEqualTo(expectedRanges);
-		assertThat(headers.getAcceptLanguageAsLocales()).element(0).isEqualTo(Locale.forLanguageTag("fr-ch"));
+		assertThat(headers.getAcceptLanguageAsLocales()).isEqualTo(List.of(
+				Locale.forLanguageTag("fr-ch"),
+				Locale.forLanguageTag("fr"),
+				Locale.forLanguageTag("en"),
+				Locale.forLanguageTag("de")));
 
 		headers.setAcceptLanguageAsLocales(Collections.singletonList(Locale.FRANCE));
-		assertThat(headers.getAcceptLanguageAsLocales()).element(0).isEqualTo(Locale.FRANCE);
+		assertThat(headers.getAcceptLanguageAsLocales()).first().isEqualTo(Locale.FRANCE);
 	}
 
 	@Test // SPR-15603