Close JarFiles when looking for Class-Path manifest entries

Fixes gh-17095

spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/ChangeableUrls.java

@@ -117,29 +117,24 @@ final class ChangeableUrls implements Iterable<URL> {
 	}
 
 	private static List<URL> getUrlsFromClassPathOfJarManifestIfPossible(URL url) {
-		JarFile jarFile = getJarFileIfPossible(url);
-		if (jarFile == null) {
-			return Collections.emptyList();
-		}
+		try {
+			File file = new File(url.toURI());
+			if (file.isFile()) {
+				try (JarFile jarFile = new JarFile(file)) {
 					try {
 						return getUrlsFromManifestClassPathAttribute(url, jarFile);
 					}
 					catch (IOException ex) {
-			throw new IllegalStateException("Failed to read Class-Path attribute from manifest of jar " + url, ex);
+						throw new IllegalStateException(
+								"Failed to read Class-Path attribute from manifest of jar " + url, ex);
 					}
 				}
-
-	private static JarFile getJarFileIfPossible(URL url) {
-		try {
-			File file = new File(url.toURI());
-			if (file.isFile()) {
-				return new JarFile(file);
 			}
 		}
 		catch (Exception ex) {
 			// Assume it's not a jar and continue
 		}
-		return null;
+		return Collections.emptyList();
 	}
 
 	private static List<URL> getUrlsFromManifestClassPathAttribute(URL jarUrl, JarFile jarFile) throws IOException {