Issue #2581: Enforce all annotations to be separate line for Checkstyle

config/checkstyle_checks.xml

@@ -108,7 +108,9 @@
     <property name="tabWidth" value="4"/>
 
     <!-- Annotations -->
-    <module name="AnnotationLocation"/>
+    <module name="AnnotationLocation">
+      <property name="allowSamelineSingleParameterlessAnnotation" value="false"/>
+    </module>
     <module name="AnnotationUseStyle"/>
     <module name="MissingDeprecated"/>
     <module name="MissingOverride">

src/test/java/com/puppycrawl/tools/checkstyle/MainTest.java

@@ -508,7 +508,8 @@ public class MainTest {
         };
 
         exit.checkAssertionAfterwards(new Assertion() {
-            @Override public void checkAssertion() throws IOException {
+            @Override
+            public void checkAssertion() throws IOException {
                 final String expectedPath = getFilePath("checks/metrics") + File.separator;
                 final StringBuilder sb = new StringBuilder();
                 sb.append("Starting audit...").append(System.getProperty("line.separator"));

src/test/java/com/puppycrawl/tools/checkstyle/TreeWalkerTest.java

@@ -48,7 +48,8 @@ import com.puppycrawl.tools.checkstyle.checks.naming.ConstantNameCheck;
 import com.puppycrawl.tools.checkstyle.checks.naming.TypeNameCheck;
 
 public class TreeWalkerTest extends BaseCheckTestSupport {
-    @Rule public final TemporaryFolder temporaryFolder = new TemporaryFolder();
+    @Rule
+    public final TemporaryFolder temporaryFolder = new TemporaryFolder();
 
     @Test
     public void testProperFileExtension() throws Exception {

src/test/java/com/puppycrawl/tools/checkstyle/checks/regexp/RegexpMultilineCheckTest.java

@@ -39,7 +39,8 @@ import com.puppycrawl.tools.checkstyle.BaseFileSetCheckTestSupport;
 import com.puppycrawl.tools.checkstyle.DefaultConfiguration;
 
 public class RegexpMultilineCheckTest extends BaseFileSetCheckTestSupport {
-    @Rule public final TemporaryFolder temporaryFolder = new TemporaryFolder();
+    @Rule
+    public final TemporaryFolder temporaryFolder = new TemporaryFolder();
 
     private DefaultConfiguration checkConfig;