docs: improve decorator

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

@@ -35,7 +35,6 @@ class AppTest {
 
   /**
    * Issue: Add at least one assertion to this test case.
-   *
    * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
    * throws an exception.
    */

decorator/src/test/java/com/iluwatar/decorator/SimpleTrollTest.java

@@ -67,7 +67,7 @@ class SimpleTrollTest {
     assertEquals(2, appender.getLogSize());
   }
 
-  private class InMemoryAppender extends AppenderBase<ILoggingEvent> {
+  private static class InMemoryAppender extends AppenderBase<ILoggingEvent> {
 
     private final List<ILoggingEvent> log = new LinkedList<>();