Merge pull request #15779 from Christoph Dreiss

* gh-15779:
  Polish "Optimize BeanPropertyName.toDashedForm()"
  Optimize BeanPropertyName.toDashedForm()

Closes gh-15779

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/BeanPropertyName.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -44,12 +44,12 @@ abstract class BeanPropertyName {
 	 */
 	public static String toDashedForm(String name, int start) {
 		StringBuilder result = new StringBuilder();
-		char[] chars = name.replace("_", "-").toCharArray();
-		for (int i = start; i < chars.length; i++) {
-			char ch = chars[i];
+		String replaced = name.replace('_', '-');
+		for (int i = start; i < replaced.length(); i++) {
+			char ch = replaced.charAt(i);
 			if (Character.isUpperCase(ch) && result.length() > 0
 					&& result.charAt(result.length() - 1) != '-') {
-				result.append("-");
+				result.append('-');
 			}
 			result.append(Character.toLowerCase(ch));
 		}