Prevent accidental Sysouts in the codebase

Author: bclozel

Diff for: spring-aop/src/main/java/org/springframework/aop/aspectj/annotation/AbstractAspectJAdvisorFactory.java

@@ -136,7 +136,6 @@ private static AspectJAnnotation findAnnotation(Method method, Class<? extends A
 
 	private static boolean compiledByAjc(Class<?> clazz) {
 		for (Field field : clazz.getDeclaredFields()) {
-			System.out.println(clazz + ": " + field.getName());
 			if (field.getName().startsWith(AJC_MAGIC)) {
 				return true;
 			}

Diff for: src/checkstyle/checkstyle-suppressions.xml

@@ -14,6 +14,7 @@
 	<suppress files="[\\/]src[\\/](test|testFixtures)[\\/](java|java21)[\\/]" checks="AnnotationLocation|AnnotationUseStyle|AtclauseOrder|AvoidNestedBlocks|FinalClass|HideUtilityClassConstructor|InnerTypeLast|JavadocStyle|JavadocType|JavadocVariable|LeftCurly|MultipleVariableDeclarations|NeedBraces|OneTopLevelClass|OuterTypeFilename|RequireThis|SpringCatch|SpringJavadoc|SpringNoThis"/>
 	<suppress files="[\\/]src[\\/](test|testFixtures)[\\/](java|java21)[\\/]" checks="RegexpSinglelineJava" id="toLowerCaseWithoutLocale"/>
 	<suppress files="[\\/]src[\\/](test|testFixtures)[\\/](java|java21)[\\/]" checks="RegexpSinglelineJava" id="toUpperCaseWithoutLocale"/>
+	<suppress files="[\\/]src[\\/](test|testFixtures)[\\/](java|java21)[\\/]" checks="RegexpSinglelineJava" id="systemOutPrintln"/>
 	<suppress files="[\\/]src[\\/](test|testFixtures)[\\/](java|java21)[\\/]org[\\/]springframework[\\/].+(Tests|Suite)" checks="IllegalImport" id="bannedJUnitJupiterImports"/>
 	<suppress files="[\\/]src[\\/](test|testFixtures)[\\/](java|java21)[\\/]" checks="SpringJUnit5" message="should not be public"/>
 
@@ -42,6 +43,7 @@
 
 	<!-- spring-core -->
 	<suppress files="[\\/]src[\\/]main[\\/]java[\\/]org[\\/]springframework[\\/](asm|cglib|objenesis|javapoet)[\\/]" checks=".*"/>
+	<suppress files="[\\/]src[\\/]main[\\/]java[\\/]org[\\/]springframework[\\/]aot[\\/]nativex[\\/]feature[\\/]" checks="RegexpSinglelineJava" id="systemOutPrintln"/>
 	<suppress files="[\\/]src[\\/]main[\\/]java[\\/]org[\\/]springframework[\\/]lang[\\/]" checks="IllegalImport" id="bannedImports" message="javax"/>
 	<suppress files="[\\/]src[\\/]main[\\/]java[\\/]org[\\/]springframework[\\/]lang[\\/]" checks="RegexpSinglelineJava" id="packageLevelNonNullApiAnnotation" />
 	<suppress files="[\\/]src[\\/]main[\\/]java[\\/]org[\\/]springframework[\\/]lang[\\/]" checks="RegexpSinglelineJava" id="packageLevelNonNullFieldsAnnotation" />
@@ -64,6 +66,7 @@
 
 	<!-- spring-jcl -->
 	<suppress files="[\\/]src[\\/]main[\\/]java[\\/]org[\\/]apache[\\/]commons[\\/]logging[\\/]" checks="Header|SpringNoThis|IllegalImport"/>
+	<suppress files="[\\/]src[\\/]main[\\/]java[\\/]org[\\/]apache[\\/]commons[\\/]logging[\\/]" checks="RegexpSinglelineJava" id="systemOutPrintln"/>
 
 	<!-- spring-jdbc -->
 	<suppress files="ResultSetWrappingSqlRowSet" checks="JavadocStyle"/>

Diff for: src/checkstyle/checkstyle.xml

@@ -237,6 +237,14 @@
 					  value="String.toUpperCase() should be String.toUpperCase(Locale.ROOT)"/>
 			<property name="ignoreComments" value="true"/>
 		</module>
+		<module name="com.puppycrawl.tools.checkstyle.checks.regexp.RegexpSinglelineJavaCheck">
+			<property name="id" value="systemOutPrintln"/>
+			<property name="format" value="System\.out\.println"/>
+			<property name="maximum" value="0"/>
+			<property name="message"
+					  value="System.out.println calls are forbidden in the main codebase"/>
+			<property name="ignoreComments" value="true"/>
+		</module>
 		<module
 			name="com.puppycrawl.tools.checkstyle.checks.regexp.RegexpSinglelineJavaCheck">
 			<property name="maximum" value="0"/>