Use ConcurrentHashMap.newKeySet

In places where a ConcurrentHashMap was used as a set by wrapping it
with Collections.newSetFromMap, switch to just using the set returned
by ConcurrentHashMap.newKeySet directly.

Closes gh-32294

spring-aop/src/main/java/org/springframework/aop/framework/autoproxy/AbstractAutoProxyCreator.java

@@ -20,7 +20,6 @@ import java.lang.reflect.Constructor;
 import java.lang.reflect.Proxy;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -136,7 +135,7 @@ public abstract class AbstractAutoProxyCreator extends ProxyProcessorSupport
 	@Nullable
 	private BeanFactory beanFactory;
 
-	private final Set<String> targetSourcedBeans = Collections.newSetFromMap(new ConcurrentHashMap<>(16));
+	private final Set<String> targetSourcedBeans = ConcurrentHashMap.newKeySet(16);
 
 	private final Map<Object, Object> earlyBeanReferences = new ConcurrentHashMap<>(16);
 

spring-beans/src/main/java/org/springframework/beans/CachedIntrospectionResults.java

@@ -23,7 +23,6 @@ import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
 import java.net.URL;
 import java.security.ProtectionDomain;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -88,7 +87,7 @@ public final class CachedIntrospectionResults {
 	 * accept classes from, even if the classes do not qualify as cache-safe.
 	 */
 	static final Set<ClassLoader> acceptedClassLoaders =
-			Collections.newSetFromMap(new ConcurrentHashMap<>(16));
+			ConcurrentHashMap.newKeySet(16);
 
 	/**
 	 * Map keyed by Class containing CachedIntrospectionResults, strongly held.

spring-beans/src/main/java/org/springframework/beans/factory/annotation/AutowiredAnnotationBeanPostProcessor.java

@@ -29,7 +29,6 @@ import java.lang.reflect.Modifier;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Iterator;
 import java.util.LinkedHashSet;
 import java.util.List;
@@ -178,7 +177,7 @@ public class AutowiredAnnotationBeanPostProcessor implements SmartInstantiationA
 	@Nullable
 	private MetadataReaderFactory metadataReaderFactory;
 
-	private final Set<String> lookupMethodsChecked = Collections.newSetFromMap(new ConcurrentHashMap<>(256));
+	private final Set<String> lookupMethodsChecked = ConcurrentHashMap.newKeySet(256);
 
 	private final Map<Class<?>, Constructor<?>[]> candidateConstructorsCache = new ConcurrentHashMap<>(256);
 

spring-beans/src/main/java/org/springframework/beans/factory/config/PropertyOverrideConfigurer.java

@@ -16,7 +16,6 @@
 
 package org.springframework.beans.factory.config;
 
-import java.util.Collections;
 import java.util.Enumeration;
 import java.util.Properties;
 import java.util.Set;
@@ -77,7 +76,7 @@ public class PropertyOverrideConfigurer extends PropertyResourceConfigurer {
 	/**
 	 * Contains names of beans that have overrides.
 	 */
-	private final Set<String> beanNames = Collections.newSetFromMap(new ConcurrentHashMap<>(16));
+	private final Set<String> beanNames = ConcurrentHashMap.newKeySet(16);
 
 
 	/**

spring-beans/src/main/java/org/springframework/beans/factory/support/AbstractBeanFactory.java

@@ -20,7 +20,6 @@ import java.beans.PropertyEditor;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
@@ -165,7 +164,7 @@ public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport imp
 	private final Map<String, RootBeanDefinition> mergedBeanDefinitions = new ConcurrentHashMap<>(256);
 
 	/** Names of beans that have already been created at least once. */
-	private final Set<String> alreadyCreated = Collections.newSetFromMap(new ConcurrentHashMap<>(256));
+	private final Set<String> alreadyCreated = ConcurrentHashMap.newKeySet(256);
 
 	/** Names of beans that are currently in creation. */
 	private final ThreadLocal<Object> prototypesCurrentlyInCreation =

spring-beans/src/main/java/org/springframework/beans/factory/support/DefaultListableBeanFactory.java

@@ -29,7 +29,6 @@ import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.IdentityHashMap;
 import java.util.Iterator;
@@ -169,7 +168,7 @@ public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFacto
 	private final Map<String, BeanDefinitionHolder> mergedBeanDefinitionHolders = new ConcurrentHashMap<>(256);
 
 	// Set of bean definition names with a primary marker. */
-	private final Set<String> primaryBeanNames = Collections.newSetFromMap(new ConcurrentHashMap<>(16));
+	private final Set<String> primaryBeanNames = ConcurrentHashMap.newKeySet(16);
 
 	/** Map of singleton and non-singleton bean names, keyed by dependency type. */
 	private final Map<Class<?>, String[]> allBeanNamesByType = new ConcurrentHashMap<>(64);

spring-beans/src/main/java/org/springframework/beans/factory/support/DefaultSingletonBeanRegistry.java

@@ -16,7 +16,6 @@
 
 package org.springframework.beans.factory.support;
 
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
@@ -91,12 +90,10 @@ public class DefaultSingletonBeanRegistry extends SimpleAliasRegistry implements
 	private final Lock singletonLock = new ReentrantLock();
 
 	/** Names of beans that are currently in creation. */
-	private final Set<String> singletonsCurrentlyInCreation =
+	private final Set<String> singletonsCurrentlyInCreation = ConcurrentHashMap.newKeySet(16);
-			Collections.newSetFromMap(new ConcurrentHashMap<>(16));
 
 	/** Names of beans currently excluded from in creation checks. */
-	private final Set<String> inCreationCheckExclusions =
+	private final Set<String> inCreationCheckExclusions = ConcurrentHashMap.newKeySet(16);
-			Collections.newSetFromMap(new ConcurrentHashMap<>(16));
 
 	@Nullable
 	private volatile Thread singletonCreationThread;

spring-context/src/main/java/org/springframework/context/event/EventListenerMethodProcessor.java

@@ -18,7 +18,6 @@ package org.springframework.context.event;
 
 import java.lang.reflect.Method;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -82,7 +81,7 @@ public class EventListenerMethodProcessor
 	@Nullable
 	private final EventExpressionEvaluator evaluator;
 
-	private final Set<Class<?>> nonAnnotatedClasses = Collections.newSetFromMap(new ConcurrentHashMap<>(64));
+	private final Set<Class<?>> nonAnnotatedClasses = ConcurrentHashMap.newKeySet(64);
 
 
 	public EventListenerMethodProcessor() {

spring-context/src/main/java/org/springframework/context/support/DefaultLifecycleProcessor.java

@@ -229,7 +229,7 @@ public class DefaultLifecycleProcessor implements LifecycleProcessor, BeanFactor
 
 	void stopForRestart() {
 		if (this.running) {
-			this.stoppedBeans = Collections.newSetFromMap(new ConcurrentHashMap<>());
+			this.stoppedBeans = ConcurrentHashMap.newKeySet();
 			stopBeans();
 			this.running = false;
 		}

spring-context/src/main/java/org/springframework/scheduling/annotation/ScheduledAnnotationBeanPostProcessor.java

@@ -20,7 +20,6 @@ import java.lang.reflect.Method;
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.IdentityHashMap;
 import java.util.LinkedHashSet;
 import java.util.List;
@@ -149,7 +148,7 @@ public class ScheduledAnnotationBeanPostProcessor
 	@Nullable
 	private TaskSchedulerRouter localScheduler;
 
-	private final Set<Class<?>> nonAnnotatedClasses = Collections.newSetFromMap(new ConcurrentHashMap<>(64));
+	private final Set<Class<?>> nonAnnotatedClasses = ConcurrentHashMap.newKeySet(64);
 
 	private final Map<Object, Set<ScheduledTask>> scheduledTasks = new IdentityHashMap<>(16);
 

spring-core/src/main/java/org/springframework/core/DecoratingClassLoader.java

@@ -16,7 +16,6 @@
 
 package org.springframework.core;
 
-import java.util.Collections;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 
@@ -39,9 +38,9 @@ public abstract class DecoratingClassLoader extends ClassLoader {
 	}
 
 
-	private final Set<String> excludedPackages = Collections.newSetFromMap(new ConcurrentHashMap<>(8));
+	private final Set<String> excludedPackages = ConcurrentHashMap.newKeySet(8);
 
-	private final Set<String> excludedClasses = Collections.newSetFromMap(new ConcurrentHashMap<>(8));
+	private final Set<String> excludedClasses = ConcurrentHashMap.newKeySet(8);
 
 
 	/**

spring-core/src/main/java/org/springframework/core/task/SimpleAsyncTaskExecutor.java

@@ -17,7 +17,6 @@
 package org.springframework.core.task;
 
 import java.io.Serializable;
-import java.util.Collections;
 import java.util.Set;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ConcurrentHashMap;
@@ -183,7 +182,7 @@ public class SimpleAsyncTaskExecutor extends CustomizableThreadCreator
 	public void setTaskTerminationTimeout(long timeout) {
 		Assert.isTrue(timeout >= 0, "Timeout value must be >=0");
 		this.taskTerminationTimeout = timeout;
-		this.activeThreads = (timeout > 0 ? Collections.newSetFromMap(new ConcurrentHashMap<>()) : null);
+		this.activeThreads = (timeout > 0 ? ConcurrentHashMap.newKeySet() : null);
 	}
 
 	/**

spring-web/src/main/java/org/springframework/web/method/annotation/SessionAttributesHandler.java

@@ -64,7 +64,7 @@ public class SessionAttributesHandler {
 
 	private final Set<Class<?>> attributeTypes = new HashSet<>();
 
-	private final Set<String> knownAttributeNames = Collections.newSetFromMap(new ConcurrentHashMap<>(4));
+	private final Set<String> knownAttributeNames = ConcurrentHashMap.newKeySet(4);
 
 	private final SessionAttributeStore sessionAttributeStore;
 

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/annotation/SessionAttributesHandler.java

@@ -42,7 +42,7 @@ class SessionAttributesHandler {
 
 	private final Set<Class<?>> attributeTypes = new HashSet<>();
 
-	private final Set<String> knownAttributeNames = Collections.newSetFromMap(new ConcurrentHashMap<>(4));
+	private final Set<String> knownAttributeNames = ConcurrentHashMap.newKeySet(4);
 
 
 	/**