diff --git a/spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/ClassLoaderFilesResourcePatternResolver.java b/spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/ClassLoaderFilesResourcePatternResolver.java
index 4d827d9810ee..da8aa7392574 100644
--- a/spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/ClassLoaderFilesResourcePatternResolver.java
+++ b/spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/ClassLoaderFilesResourcePatternResolver.java
@@ -123,15 +123,13 @@ public Resource[] getResources(String locationPattern) throws IOException {
 	private List<Resource> getAdditionalResources(String locationPattern) throws MalformedURLException {
 		List<Resource> additionalResources = new ArrayList<>();
 		String trimmedLocationPattern = trimLocationPattern(locationPattern);
-		for (SourceDirectory sourceDirectory : this.classLoaderFiles.getSourceDirectories()) {
-			for (Entry<String, ClassLoaderFile> entry : sourceDirectory.getFilesEntrySet()) {
-				String name = entry.getKey();
-				ClassLoaderFile file = entry.getValue();
-				if (file.getKind() != Kind.DELETED && this.antPathMatcher.match(trimmedLocationPattern, name)) {
-					URL url = new URL("reloaded", null, -1, "/" + name, new ClassLoaderFileURLStreamHandler(file));
-					UrlResource resource = new UrlResource(url);
-					additionalResources.add(resource);
-				}
+		for (Entry<String, ClassLoaderFile> entry : this.classLoaderFiles.getFileEntries()) {
+			String name = entry.getKey();
+			ClassLoaderFile file = entry.getValue();
+			if (file.getKind() != Kind.DELETED && this.antPathMatcher.match(trimmedLocationPattern, name)) {
+				URL url = new URL("reloaded", null, -1, "/" + name, new ClassLoaderFileURLStreamHandler(file));
+				UrlResource resource = new UrlResource(url);
+				additionalResources.add(resource);
 			}
 		}
 		return additionalResources;
@@ -147,20 +145,18 @@ private String trimLocationPattern(String pattern) {
 	}
 
 	private boolean isDeleted(Resource resource) {
-		for (SourceDirectory sourceDirectory : this.classLoaderFiles.getSourceDirectories()) {
-			for (Entry<String, ClassLoaderFile> entry : sourceDirectory.getFilesEntrySet()) {
-				try {
-					String name = entry.getKey();
-					ClassLoaderFile file = entry.getValue();
-					if (file.getKind() == Kind.DELETED && resource.exists()
-							&& resource.getURI().toString().endsWith(name)) {
-						return true;
-					}
-				}
-				catch (IOException ex) {
-					throw new IllegalStateException("Failed to retrieve URI from '" + resource + "'", ex);
+		for (Entry<String, ClassLoaderFile> entry : this.classLoaderFiles.getFileEntries()) {
+			try {
+				String name = entry.getKey();
+				ClassLoaderFile file = entry.getValue();
+				if (file.getKind() == Kind.DELETED && resource.exists()
+						&& resource.getURI().toString().endsWith(name)) {
+					return true;
 				}
 			}
+			catch (IOException ex) {
+				throw new IllegalStateException("Failed to retrieve URI from '" + resource + "'", ex);
+			}
 		}
 		return false;
 	}
diff --git a/spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/classloader/ClassLoaderFiles.java b/spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/classloader/ClassLoaderFiles.java
index 1def6fd05b1f..8b4ee7e5c5d3 100644
--- a/spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/classloader/ClassLoaderFiles.java
+++ b/spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/classloader/ClassLoaderFiles.java
@@ -43,11 +43,18 @@ public class ClassLoaderFiles implements ClassLoaderFileRepository, Serializable
 
 	private final Map<String, SourceDirectory> sourceDirectories;
 
+	/**
+	 * A flattened map of all files from all source directories for fast, O(1) lookups.
+	 * The key is the file's relative path, and the value is the ClassLoaderFile.
+	 */
+	private final Map<String, ClassLoaderFile> filesByName;
+
 	/**
 	 * Create a new {@link ClassLoaderFiles} instance.
 	 */
 	public ClassLoaderFiles() {
 		this.sourceDirectories = new LinkedHashMap<>();
+		this.filesByName = new LinkedHashMap<>();
 	}
 
 	/**
@@ -57,6 +64,7 @@ public ClassLoaderFiles() {
 	public ClassLoaderFiles(ClassLoaderFiles classLoaderFiles) {
 		Assert.notNull(classLoaderFiles, "'classLoaderFiles' must not be null");
 		this.sourceDirectories = new LinkedHashMap<>(classLoaderFiles.sourceDirectories);
+		this.filesByName = new LinkedHashMap<>(classLoaderFiles.filesByName);
 	}
 
 	/**
@@ -94,12 +102,14 @@ public void addFile(String sourceDirectory, String name, ClassLoaderFile file) {
 		Assert.notNull(file, "'file' must not be null");
 		removeAll(name);
 		getOrCreateSourceDirectory(sourceDirectory).add(name, file);
+		this.filesByName.put(name, file);
 	}
 
 	private void removeAll(String name) {
 		for (SourceDirectory sourceDirectory : this.sourceDirectories.values()) {
 			sourceDirectory.remove(name);
 		}
+		this.filesByName.remove(name);
 	}
 
 	/**
@@ -125,22 +135,21 @@ public Collection<SourceDirectory> getSourceDirectories() {
 	 * @return the size of the collection
 	 */
 	public int size() {
-		int size = 0;
-		for (SourceDirectory sourceDirectory : this.sourceDirectories.values()) {
-			size += sourceDirectory.getFiles().size();
-		}
-		return size;
+		return this.filesByName.size();
 	}
 
 	@Override
 	public ClassLoaderFile getFile(String name) {
-		for (SourceDirectory sourceDirectory : this.sourceDirectories.values()) {
-			ClassLoaderFile file = sourceDirectory.get(name);
-			if (file != null) {
-				return file;
-			}
-		}
-		return null;
+		return this.filesByName.get(name);
+	}
+
+	/**
+	 * Returns a set of all file entries across all source directories for efficient
+	 * iteration.
+	 * @return a set of all file entries
+	 */
+	public Set<Entry<String, ClassLoaderFile>> getFileEntries() {
+		return Collections.unmodifiableSet(this.filesByName.entrySet());
 	}
 
 	/**