Optimization in ResourceArrayPropertyEditor

The previous implementation uses ArrayList for storing resolved
resources and ArrayList has O(n) time complexity for the contains
operation. By switching to the HashSet for storing resolved
resources we improve the time complexity of this operation to be O(1).

See gh-25927

spring-core/src/main/java/org/springframework/core/io/support/ResourceArrayPropertyEditor.java

@@ -18,10 +18,10 @@ package org.springframework.core.io.support;
 
 import java.beans.PropertyEditorSupport;
 import java.io.IOException;
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.List;
+import java.util.HashSet;
+import java.util.Set;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -129,7 +129,7 @@ public class ResourceArrayPropertyEditor extends PropertyEditorSupport {
 	public void setValue(Object value) throws IllegalArgumentException {
 		if (value instanceof Collection || (value instanceof Object[] && !(value instanceof Resource[]))) {
 			Collection<?> input = (value instanceof Collection ? (Collection<?>) value : Arrays.asList((Object[]) value));
-			List<Resource> merged = new ArrayList<>();
+			Set<Resource> merged = new HashSet<>(input.size());
 			for (Object element : input) {
 				if (element instanceof String) {
 					// A location pattern: resolve it into a Resource array.
@@ -137,11 +137,7 @@ public class ResourceArrayPropertyEditor extends PropertyEditorSupport {
 					String pattern = resolvePath((String) element).trim();
 					try {
 						Resource[] resources = this.resourcePatternResolver.getResources(pattern);
-						for (Resource resource : resources) {
+						merged.addAll(Arrays.asList(resources));
-							if (!merged.contains(resource)) {
-								merged.add(resource);
-							}
-						}
 					}
 					catch (IOException ex) {
 						// ignore - might be an unresolved placeholder or non-existing base directory
@@ -152,10 +148,7 @@ public class ResourceArrayPropertyEditor extends PropertyEditorSupport {
 				}
 				else if (element instanceof Resource) {
 					// A Resource object: add it to the result.
-					Resource resource = (Resource) element;
+					merged.add((Resource) element);
-					if (!merged.contains(resource)) {
-						merged.add(resource);
-					}
 				}
 				else {
 					throw new IllegalArgumentException("Cannot convert element [" + element + "] to [" +