Only add AddMissingMethodImplementation templates to Java sources

src/main/java/org/openrewrite/java/migrate/AddMissingMethodImplementation.java

@@ -27,6 +27,7 @@
 import org.openrewrite.java.tree.J;
 import org.openrewrite.java.tree.JavaType;
 import org.openrewrite.java.tree.TypeUtils;
+import org.openrewrite.staticanalysis.java.JavaFileChecker;
 
 import java.util.Iterator;
 
@@ -57,7 +58,10 @@ public class AddMissingMethodImplementation extends Recipe {
 
     @Override
     public TreeVisitor<?, ExecutionContext> getVisitor() {
-        return Preconditions.check(new UsesType<>(fullyQualifiedClassName, true), new ClassImplementationVisitor());
+        // The method template is Java, so printing it into a Kotlin or Groovy class would not compile.
+        return Preconditions.check(
+                Preconditions.and(new JavaFileChecker<>(), new UsesType<>(fullyQualifiedClassName, true)),
+                new ClassImplementationVisitor());
     }
 
     public class ClassImplementationVisitor extends JavaIsoVisitor<ExecutionContext> {

src/test/java/org/openrewrite/java/migrate/AddMissingMethodImplementationTest.java

@@ -23,6 +23,7 @@
 
 import static org.openrewrite.java.Assertions.java;
 import static org.openrewrite.java.Assertions.javaVersion;
+import static org.openrewrite.kotlin.Assertions.kotlin;
 
 class AddMissingMethodImplementationTest implements RewriteTest {
 
@@ -234,4 +235,18 @@ class C2 {
           )
         );
     }
+
+    @Test
+    void leaveKotlinAlone() {
+        rewriteRun(
+          spec -> spec.recipe(new AddMissingMethodImplementation("java.lang.Runnable", "java.lang.Runnable run()",
+            "public void run() { }")),
+          //language=kotlin
+          kotlin(
+            """
+              class Delegating(runnable: Runnable) : Runnable by runnable
+              """
+          )
+        );
+    }
 }