Fixes Checkstyle problems

There are few checkstyles problems found in the  which are required to be fixed

mutex/src/test/java/com/iluwatar/mutex/AppTest.java

@@ -28,7 +28,7 @@ import java.io.IOException;
 /**
  * Application Test Entrypoint
  */
-public class AppTest{
+public class AppTest {
   @Test
   public void test() throws IOException {
     String[] args = {};