update

src/main/java/rocks/zipcode/io/quiz4/collections/ComparableTreeSet.java

     public ComparableTreeSet() {
     }
 
-    public Integer compareTo(ComparableTreeSet<_> o) {
-        return null;
+    public int compareTo(ComparableTreeSet<_> o) {
+        return Integer.valueOf(null);
     }
 }

src/test/java/rocks/zipcode/io/quiz4/objectorientation/palindromeobject/PalindromeObjectIsPalindromeTestNegative.java

     }
 
     public void test(String input) {
-        Assert.assertTrue(new PalindromeObject(input).isPalindrome());
+        Assert.assertFalse(new PalindromeObject(input).isPalindrome());
     }
 }