Add note about absence of annotated APIs in case there are none

Author: marcphilipp

documentation/src/docs/asciidoc/user-guide/api-evolution.adoc

@@ -40,15 +40,15 @@ value of lower stability.
 [[api-evolution-experimental-apis]]
 === Experimental APIs
 
-The following table lists which APIs are currently designated as _experimental_ via
+The following tables list which APIs are currently designated as _experimental_ via
 `@API(status = EXPERIMENTAL)`. Caution should be taken when relying on such APIs.
 
 include::{experimentalApisTableFile}[]
 
 [[api-evolution-deprecated-apis]]
 === Deprecated APIs
 
-The following table lists which APIs are currently designated as _deprecated_ via
+The following tables list which APIs are currently designated as _deprecated_ via
 `@API(status = DEPRECATED)`. You should avoid using deprecated APIs whenever possible,
 since such APIs will likely be removed in an upcoming release.
 

documentation/src/tools/java/org/junit/api/tools/AbstractApiReportWriter.java

@@ -16,6 +16,7 @@
 
 import java.io.PrintWriter;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.TreeMap;
 
@@ -52,22 +53,27 @@ public void printDeclarationInfo(PrintWriter out, Set<Status> statuses) {
 	protected void printDeclarationSection(Set<Status> statuses, Status status, List<Declaration> declarations,
 			PrintWriter out) {
 		printDeclarationSectionHeader(statuses, status, declarations, out);
-		declarations.stream() //
-				.collect(groupingBy(Declaration::moduleName, TreeMap::new, toList())) //
-				.forEach((moduleName, moduleDeclarations) -> {
-					out.println(h4("Module " + moduleName));
-					out.println();
-					moduleDeclarations.stream() //
-							.collect(groupingBy(Declaration::packageName, TreeMap::new, toList())) //
-							.forEach((packageName, packageDeclarations) -> {
-								out.println(h5("Package " + packageName));
-								out.println();
-								printDeclarationTableHeader(out);
-								packageDeclarations.forEach(it -> printDeclarationTableRow(it, out));
-								printDeclarationTableFooter(out);
-								out.println();
-							});
-				});
+		Map<String, List<Declaration>> declarationsByModule = declarations.stream() //
+				.collect(groupingBy(Declaration::moduleName, TreeMap::new, toList()));
+		if (declarationsByModule.isEmpty()) {
+			out.println(paragraph("NOTE: There are currently no APIs annotated with %s.".formatted(
+				code("@API(status = %s)".formatted(status.name())))));
+			return;
+		}
+		declarationsByModule.forEach((moduleName, moduleDeclarations) -> {
+			out.println(h4("Module " + moduleName));
+			out.println();
+			moduleDeclarations.stream() //
+					.collect(groupingBy(Declaration::packageName, TreeMap::new, toList())) //
+					.forEach((packageName, packageDeclarations) -> {
+						out.println(h5("Package " + packageName));
+						out.println();
+						printDeclarationTableHeader(out);
+						packageDeclarations.forEach(it -> printDeclarationTableRow(it, out));
+						printDeclarationTableFooter(out);
+						out.println();
+					});
+		});
 	}
 
 	protected void printDeclarationSectionHeader(Set<Status> statuses, Status status, List<Declaration> declarations,