example Java class with `@NotNull` annotation

src/main/java/org/jetbrains/plugins/template/services/JavaService.java

@@ -0,0 +1,18 @@
+package org.jetbrains.plugins.template.services;
+
+import com.intellij.openapi.components.Service;
+import org.jetbrains.annotations.NotNull;
+
+@Service(Service.Level.PROJECT)
+public final class JavaService {
+
+    public JavaService() {
+        System.out.println("FOO1");
+
+        getRandomNumber(null);
+    }
+
+    public String getRandomNumber(@NotNull String text) {
+        return text.replaceAll("[^0-9]", ""); // set a breakpoint here and debug the `runIde` task
+    }
+}

src/main/kotlin/org/jetbrains/plugins/template/listeners/MyApplicationActivationListener.kt

@@ -1,12 +1,17 @@
 package org.jetbrains.plugins.template.listeners
 
 import com.intellij.openapi.application.ApplicationActivationListener
+import com.intellij.openapi.components.service
 import com.intellij.openapi.diagnostic.thisLogger
 import com.intellij.openapi.wm.IdeFrame
+import org.jetbrains.plugins.template.services.JavaService
 
 internal class MyApplicationActivationListener : ApplicationActivationListener {
 
     override fun applicationActivated(ideFrame: IdeFrame) {
         thisLogger().warn("Don't forget to remove all non-needed sample code files with their corresponding registration entries in `plugin.xml`.")
+
+        val service = ideFrame.project?.service<JavaService>()
+        println("service = ${service}")
     }
 }