Upgrade to checkstyle 9.0.1

Closes gh-302

Author: philwebb

pom.xml

@@ -39,7 +39,7 @@
 		<ant-contrib.version>1.0b3</ant-contrib.version>
 		<asm.version>7.3.1</asm.version>
 		<assertj.version>3.8.0</assertj.version>
-		<checkstyle.version>8.45.1</checkstyle.version>
+		<checkstyle.version>9.0.1</checkstyle.version>
 		<gradle.version>3.4</gradle.version>
 		<groovy.version>2.4.21</groovy.version>
 		<log4j.version>2.14.1</log4j.version>

spring-javaformat/spring-javaformat-checkstyle/src/main/java/io/spring/javaformat/checkstyle/check/SpringJavadocCheck.java

@@ -167,7 +167,7 @@ private void checkSinceTag(DetailAST ast, TextBlock javadoc) {
 		String[] text = javadoc.getText();
 		DetailAST interfaceDef = getInterfaceDef(ast);
 		boolean privateType = !isPublicOrProtected(ast) && (interfaceDef == null || !isPublicOrProtected(interfaceDef));
-		boolean innerType = ast.getParent() != null;
+		boolean innerType = ast.getParent() != null && ast.getParent().getType() != TokenTypes.COMPILATION_UNIT;
 		boolean found = false;
 		for (int i = 0; i < text.length; i++) {
 			Matcher matcher = SINCE_TAG_PATTERN.matcher(text[i]);