diff --git a/marker/src/main/java/App.java b/marker/src/main/java/App.java
index 384c999dc..c7b4530c6 100644
--- a/marker/src/main/java/App.java
+++ b/marker/src/main/java/App.java
@@ -21,9 +21,6 @@
  * THE SOFTWARE.
  */
 
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
 /**
  * Created by Alexis on 28-Apr-17. With Marker interface idea is to make empty interface and extend
  * it. Basically it is just to identify the special objects from normal objects. Like in case of
@@ -46,22 +43,10 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
-
-    final Logger logger = LoggerFactory.getLogger(App.class);
-    Guard guard = new Guard();
-    Thief thief = new Thief();
-
-    if (guard instanceof Permission) {
-      guard.enter();
-    } else {
-      logger.info("You have no permission to enter, please leave this area");
-    }
-
-    if (thief instanceof Permission) {
-      thief.steal();
-    } else {
-      thief.doNothing();
-    }
+    var guard = new Guard();
+    var thief = new Thief();
+    guard.enter();
+    thief.doNothing();
   }
 }
 
diff --git a/marker/src/main/java/Guard.java b/marker/src/main/java/Guard.java
index 9a57e15fd..54443603c 100644
--- a/marker/src/main/java/Guard.java
+++ b/marker/src/main/java/Guard.java
@@ -31,8 +31,7 @@ public class Guard implements Permission {
 
   private static final Logger LOGGER = LoggerFactory.getLogger(Guard.class);
 
-  protected static void enter() {
-
+  protected void enter() {
     LOGGER.info("You can enter");
   }
 }
diff --git a/marker/src/main/java/Thief.java b/marker/src/main/java/Thief.java
index 341eae377..22155ef7b 100644
--- a/marker/src/main/java/Thief.java
+++ b/marker/src/main/java/Thief.java
@@ -35,7 +35,7 @@ public class Thief {
     LOGGER.info("Steal valuable items");
   }
 
-  protected static void doNothing() {
+  protected void doNothing() {
     LOGGER.info("Pretend nothing happened and just leave");
   }
 }
diff --git a/marker/src/test/java/AppTest.java b/marker/src/test/java/AppTest.java
index 5d63db0ad..13295a9e5 100644
--- a/marker/src/test/java/AppTest.java
+++ b/marker/src/test/java/AppTest.java
@@ -30,7 +30,6 @@ public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
-    App.main(args);
+    App.main(new String[]{});
   }
 }
diff --git a/marker/src/test/java/GuardTest.java b/marker/src/test/java/GuardTest.java
index 615d4e129..ae92c27dc 100644
--- a/marker/src/test/java/GuardTest.java
+++ b/marker/src/test/java/GuardTest.java
@@ -33,7 +33,7 @@ public class GuardTest {
 
   @Test
   public void testGuard() {
-    Guard guard = new Guard();
+    var guard = new Guard();
     assertThat(guard, instanceOf(Permission.class));
   }
 }
\ No newline at end of file
diff --git a/marker/src/test/java/ThiefTest.java b/marker/src/test/java/ThiefTest.java
index 2732fc78a..dc081acf8 100644
--- a/marker/src/test/java/ThiefTest.java
+++ b/marker/src/test/java/ThiefTest.java
@@ -21,9 +21,11 @@
  * THE SOFTWARE.
  */
 
-import org.junit.jupiter.api.Test;
+import static org.hamcrest.CoreMatchers.instanceOf;
+import static org.hamcrest.CoreMatchers.not;
+import static org.hamcrest.MatcherAssert.assertThat;
 
-import static org.junit.jupiter.api.Assertions.assertFalse;
+import org.junit.jupiter.api.Test;
 
 /**
  * Thief test
@@ -31,7 +33,7 @@ import static org.junit.jupiter.api.Assertions.assertFalse;
 public class ThiefTest {
   @Test
   public void testThief() {
-    Thief thief = new Thief();
-    assertFalse(thief instanceof Permission);
+    var thief = new Thief();
+    assertThat(thief, not(instanceOf(Permission.class)));
   }
 }
\ No newline at end of file