Avoid creating unnecessary garbage during URL normalization

Closes gh-11207

spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/jar/Handler.java

@@ -48,6 +48,10 @@ public class Handler extends URLStreamHandler {
 
 	private static final String SEPARATOR = "!/";
 
+	private static final String CURRENT_DIR = "/./";
+
+	private static final String PARENT_DIR = "/../";
+
 	private static final String[] FALLBACK_HANDLERS = {
 			"sun.net.www.protocol.jar.Handler" };
 
@@ -207,6 +211,9 @@ public class Handler extends URLStreamHandler {
 	}
 
 	private String normalize(String file) {
+		if (!file.contains(CURRENT_DIR) && !file.contains(PARENT_DIR)) {
+			return file;
+		}
 		int afterLastSeparatorIndex = file.lastIndexOf(SEPARATOR) + SEPARATOR.length();
 		String afterSeparator = file.substring(afterLastSeparatorIndex);
 		afterSeparator = replaceParentDir(afterSeparator);
@@ -216,7 +223,7 @@ public class Handler extends URLStreamHandler {
 
 	private String replaceParentDir(String file) {
 		int parentDirIndex;
-		while ((parentDirIndex = file.indexOf("/../")) >= 0) {
+		while ((parentDirIndex = file.indexOf(PARENT_DIR)) >= 0) {
 			int precedingSlashIndex = file.lastIndexOf('/', parentDirIndex - 1);
 			if (precedingSlashIndex >= 0) {
 				file = file.substring(0, precedingSlashIndex)
@@ -230,7 +237,7 @@ public class Handler extends URLStreamHandler {
 	}
 
 	private String replaceCurrentDir(String file) {
-		return file.replace("/./", "/");
+		return file.replace(CURRENT_DIR, "/");
 	}
 
 	@Override