uncomment classes in core-java (#1777)

* uncomment classes in core-java

* Add content to guide to JDO

core-java/src/test/java/com/baeldung/java8/comparator/Employee.java

@@ -1,6 +1,4 @@
 package com.baeldung.java8.comparator;
-/*    
-
 import lombok.AllArgsConstructor;
 import lombok.Data;
 import lombok.EqualsAndHashCode;
@@ -22,4 +20,3 @@ public class Employee implements Comparable<Employee>{
     }
     
 }
-*/

core-java/src/test/java/com/baeldung/java8/comparator/Java8ComparatorTest.java

@@ -1,5 +1,4 @@
 package com.baeldung.java8.comparator;
-/*
 import java.util.Arrays;
 import java.util.Comparator;
 
@@ -164,5 +163,3 @@ public class Java8ComparatorTest {
 
 
 }
-
-*/