Optimize some StringBuilder.append() calls

Closes gh-13961

spring-boot-project/spring-boot-cli/src/main/java/org/springframework/boot/cli/command/archive/ArchiveCommand.java

@@ -230,7 +230,9 @@ abstract class ArchiveCommand extends OptionParsingCommand {
 		private String commaDelimitedClassNames(Class<?>[] classes) {
 			StringBuilder builder = new StringBuilder();
 			for (int i = 0; i < classes.length; i++) {
-				builder.append((i != 0) ? "," : "");
+				if (i != 0) {
+					builder.append(',');
+				}
 				builder.append(classes[i].getName());
 			}
 			return builder.toString();