From 0eb64bdcde3f8885f17a3446ac521f090aee84e3 Mon Sep 17 00:00:00 2001
From: Patrick Strawderman <pstrawderman@netflix.com>
Date: Fri, 14 Nov 2025 12:55:11 -0800
Subject: [PATCH] Fix single-check idiom in UnmodifiableMultiValueMap

Read the respective fields only once in values, entrySet, and keySet methods.

Signed-off-by: Patrick Strawderman <pstrawderman@netflix.com>
---
 .../util/UnmodifiableMultiValueMap.java       | 25 +++++++++++--------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/spring-core/src/main/java/org/springframework/util/UnmodifiableMultiValueMap.java b/spring-core/src/main/java/org/springframework/util/UnmodifiableMultiValueMap.java
index 8db025670c2c..54766301b7a6 100644
--- a/spring-core/src/main/java/org/springframework/util/UnmodifiableMultiValueMap.java
+++ b/spring-core/src/main/java/org/springframework/util/UnmodifiableMultiValueMap.java
@@ -141,26 +141,32 @@ public String toString() {
 
 	@Override
 	public Set<K> keySet() {
-		if (this.keySet == null) {
-			this.keySet = Collections.unmodifiableSet(this.delegate.keySet());
+		Set<K> keySet = this.keySet;
+		if (keySet == null) {
+			keySet = Collections.unmodifiableSet(this.delegate.keySet());
+			this.keySet = keySet;
 		}
-		return this.keySet;
+		return keySet;
 	}
 
 	@Override
 	public Set<Entry<K, List<V>>> entrySet() {
-		if (this.entrySet == null) {
-			this.entrySet = new UnmodifiableEntrySet<>(this.delegate.entrySet());
+		Set<Entry<K, List<V>>> entrySet = this.entrySet;
+		if (entrySet == null) {
+			entrySet = new UnmodifiableEntrySet<>(this.delegate.entrySet());
+			this.entrySet = entrySet;
 		}
-		return this.entrySet;
+		return entrySet;
 	}
 
 	@Override
 	public Collection<List<V>> values() {
-		if (this.values == null) {
-			this.values = new UnmodifiableValueCollection<>(this.delegate.values());
+		Collection<List<V>> values = this.values;
+		if (values == null) {
+			values = new UnmodifiableValueCollection<>(this.delegate.values());
+			this.values = values;
 		}
-		return this.values;
+		return values;
 	}
 
 	// unsupported
@@ -406,7 +412,6 @@ public void clear() {
 			throw new UnsupportedOperationException();
 		}
 
-
 		private static class UnmodifiableEntrySpliterator<K,V> implements Spliterator<Entry<K,List<V>>> {
 
 			private final Spliterator<Entry<K, List<V>>> delegate;