Polish 'Fix infinite loop in FieldValues'

See gh-22040

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationsample/fieldvalues/FieldValues.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -108,7 +108,7 @@ public class FieldValues {
 
 	private Integer[] integerArray = new Integer[] { 42, 24 };
 
-	private FieldValues[] unknownArray;
+	private UnknownElementType[] unknownArray = new UnknownElementType[] { new UnknownElementType() };
 
 	private Duration durationNone;
 

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationsample/fieldvalues/UnknownElementType.java

+/*
+ * Copyright 2012-2020 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.configurationsample.fieldvalues;
+
+/**
+ * Type used to check unknown array element types.
+ *
+ * @author Phillip Webb
+ */
+public class UnknownElementType {
+
+}