Fix locale parsing error with en_en, tr_tr, etc

Previously, StringUtils#parseLocaleString would parse locale strings
having the same lowercase token for both language and country
incorrectly, e.g. 'tr_tr' would parse to 'tr_TR_tr' as opposed to the
expected 'tr_TR'.

This commit fixes this behavior by using using String#lastIndexOf
instead of String#indexOf when determining the location of the country
code token.

Issue: SPR-9420

spring-core/src/main/java/org/springframework/util/StringUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 the original author or authors.
+ * Copyright 2002-2012 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.
@@ -674,7 +674,7 @@ public abstract class StringUtils {
 		if (parts.length >= 2) {
 			// There is definitely a variant, and it is everything after the country
 			// code sans the separator between the country code and the variant.
-			int endIndexOfCountryCode = localeString.indexOf(country) + country.length();
+			int endIndexOfCountryCode = localeString.lastIndexOf(country) + country.length();
 			// Strip off any leading '_' and whitespace, what's left is the variant.
 			variant = trimLeadingWhitespace(localeString.substring(endIndexOfCountryCode));
 			if (variant.startsWith("_")) {