Fix getCacheNames() concurrent access in NoOpCacheManager

Closes gh-35842

spring-context/src/main/java/org/springframework/cache/support/NoOpCacheManager.java

@@ -18,8 +18,6 @@ package org.springframework.cache.support;
 
 import java.util.Collection;
 import java.util.Collections;
-import java.util.LinkedHashSet;
-import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 
@@ -33,44 +31,28 @@ import org.springframework.cache.CacheManager;
  * for disabling caching, typically used for backing cache declarations
  * without an actual backing store.
  *
- * <p>Will simply accept any items into the cache not actually storing them.
+ * <p>This implementation will simply accept any items into the cache,
+ * not actually storing them.
  *
  * @author Costin Leau
  * @author Stephane Nicoll
+ * @author Juergen Hoeller
  * @since 3.1
  * @see NoOpCache
  */
 public class NoOpCacheManager implements CacheManager {
 
-	private final ConcurrentMap<String, Cache> caches = new ConcurrentHashMap<>(16);
-
-	private final Set<String> cacheNames = new LinkedHashSet<>(16);
+	private final ConcurrentMap<String, Cache> cacheMap = new ConcurrentHashMap<>(16);
 
 
-	/**
-	 * This implementation always returns a {@link Cache} implementation that will not store items.
-	 * Additionally, the request cache will be remembered by the manager for consistency.
-	 */
 	@Override
 	public @Nullable Cache getCache(String name) {
-		Cache cache = this.caches.get(name);
-		if (cache == null) {
-			this.caches.computeIfAbsent(name, NoOpCache::new);
-			synchronized (this.cacheNames) {
-				this.cacheNames.add(name);
-			}
-		}
-		return this.caches.get(name);
+		return this.cacheMap.computeIfAbsent(name, NoOpCache::new);
 	}
 
-	/**
-	 * This implementation returns the name of the caches previously requested.
-	 */
 	@Override
 	public Collection<String> getCacheNames() {
-		synchronized (this.cacheNames) {
-			return Collections.unmodifiableSet(this.cacheNames);
-		}
+		return Collections.unmodifiableSet(this.cacheMap.keySet());
 	}
 
 }