Avoid creation of unnecessary collections

Closes spring-projectsgh-14916

Author: dreis2211

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/web/reactive/ControllerEndpointHandlerMapping.java

@@ -17,10 +17,8 @@
 package org.springframework.boot.actuate.endpoint.web.reactive;
 
 import java.lang.reflect.Method;
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.Set;
@@ -95,7 +93,7 @@ private RequestMappingInfo withEndpointMappedPatterns(
 			ExposableControllerEndpoint endpoint, RequestMappingInfo mapping) {
 		Set<PathPattern> patterns = mapping.getPatternsCondition().getPatterns();
 		if (patterns.isEmpty()) {
-			patterns = new HashSet<>(Arrays.asList(getPathPatternParser().parse("")));
+			patterns = Collections.singleton(getPathPatternParser().parse(""));
 		}
 		PathPattern[] endpointMappedPatterns = patterns.stream()
 				.map((pattern) -> getEndpointMappedPattern(endpoint, pattern))

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/web/servlet/ControllerEndpointHandlerMapping.java

@@ -19,7 +19,6 @@
 import java.lang.reflect.Method;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -95,7 +94,7 @@ private RequestMappingInfo withEndpointMappedPatterns(
 			ExposableControllerEndpoint endpoint, RequestMappingInfo mapping) {
 		Set<String> patterns = mapping.getPatternsCondition().getPatterns();
 		if (patterns.isEmpty()) {
-			patterns = new HashSet<>(Collections.singletonList(""));
+			patterns = Collections.singleton("");
 		}
 		String[] endpointMappedPatterns = patterns.stream()
 				.map((pattern) -> getEndpointMappedPattern(endpoint, pattern))

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/ConfigurationMetadataAnnotationProcessor.java

@@ -20,9 +20,7 @@
 import java.io.PrintWriter;
 import java.io.StringWriter;
 import java.time.Duration;
-import java.util.Arrays;
 import java.util.Collections;
-import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.LinkedList;
 import java.util.List;
@@ -97,8 +95,8 @@ public class ConfigurationMetadataAnnotationProcessor extends AbstractProcessor
 
 	static final String LOMBOK_ACCESS_LEVEL_PUBLIC = "PUBLIC";
 
-	private static final Set<String> SUPPORTED_OPTIONS = Collections.unmodifiableSet(
-			new HashSet<>(Arrays.asList(ADDITIONAL_METADATA_LOCATIONS_OPTION)));
+	private static final Set<String> SUPPORTED_OPTIONS = Collections
+			.unmodifiableSet(Collections.singleton(ADDITIONAL_METADATA_LOCATIONS_OPTION));
 
 	private MetadataStore metadataStore;
 

spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/DefaultLaunchScript.java

@@ -23,9 +23,7 @@
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.nio.charset.StandardCharsets;
-import java.util.Arrays;
 import java.util.Collections;
-import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
 import java.util.regex.Matcher;
@@ -48,7 +46,7 @@ public class DefaultLaunchScript implements LaunchScript {
 			.compile("\\{\\{(\\w+)(:.*?)?\\}\\}(?!\\})");
 
 	private static final Set<String> FILE_PATH_KEYS = Collections
-			.unmodifiableSet(new HashSet<>(Arrays.asList("inlinedConfScript")));
+			.unmodifiableSet(Collections.singleton("inlinedConfScript"));
 
 	private final String content;