Efficient checks for empty strings and single character matches

Closes gh-25552
Closes gh-25553

spring-test/src/main/java/org/springframework/test/context/jdbc/MergedSqlConfig.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -235,7 +235,7 @@ class MergedSqlConfig {
 
 	private static String getString(AnnotationAttributes attributes, String attributeName, String defaultValue) {
 		String value = attributes.getString(attributeName);
-		if ("".equals(value)) {
+		if (value.isEmpty()) {
 			value = defaultValue;
 		}
 		return value;