AddressBook: remove unused containsTag()

AddressBook#containsTag() checks if a given Tag is in the master list of
Tags. However this method is not used anywhere as there are no commands
that support it, and is not part of any learning objectives. While it is
used in two tests for AddressBook#addPerson(),
AddressBook#containsTag(Tag):boolean is used infrequently enough to
justify superseding it with AddressBook#getAllTags():UniqueTagList and
UniqueTagList#contains(Tag).

Let's remove AddressBook#containsTag() as unused code contributes to
maintenance and comprehension overheads.

src/seedu/addressbook/data/AddressBook.java

@@ -90,13 +90,6 @@ public boolean containsPerson(ReadOnlyPerson key) {
         return allPersons.contains(key);
     }
 
-    /**
-     * Returns true if an equivalent person exists in the address book.
-     */
-    public boolean containsTag(Tag key) {
-        return allTags.contains(key);
-    }
-
     /**
      * Removes the equivalent person from the address book.
      *

test/java/seedu/addressbook/data/AddressBookTest.java

@@ -91,11 +91,11 @@ public void addPerson_emptyAddressBook() throws Exception {
 
     @Test
     public void addPerson_someTagsNotInTagList() throws Exception {
-        assertFalse(defaultAddressBook.containsTag(tagEconomist));
-        assertFalse(defaultAddressBook.containsTag(tagPrizeWinner));
+        assertFalse(defaultAddressBook.getAllTags().contains(tagEconomist));
+        assertFalse(defaultAddressBook.getAllTags().contains(tagPrizeWinner));
         defaultAddressBook.addPerson(davidElliot);
-        assertTrue(defaultAddressBook.containsTag(tagEconomist));
-        assertTrue(defaultAddressBook.containsTag(tagPrizeWinner));
+        assertTrue(defaultAddressBook.getAllTags().contains(tagEconomist));
+        assertTrue(defaultAddressBook.getAllTags().contains(tagPrizeWinner));
 
         assertTrue(isTagObjectInAddressBookList(tagEconomist, defaultAddressBook));
         assertTrue(isTagObjectInAddressBookList(tagPrizeWinner, defaultAddressBook));
@@ -117,7 +117,7 @@ public void addPerson_personAlreadyInListButHasTagNotInList_tagNotAdded() throws
             // ignore expected exception
         }
 
-        assertFalse(defaultAddressBook.containsTag(tagPrizeWinner));
+        assertFalse(defaultAddressBook.getAllTags().contains(tagPrizeWinner));
     }
 
     @Test
@@ -139,25 +139,6 @@ public void containsPerson() throws Exception {
         }
     }
 
-    @Test
-    public void containsTag() throws Exception {
-        UniqueTagList tagsWhichShouldBeIn = new UniqueTagList(tagMathematician, tagScientist);
-        UniqueTagList tagsWHichShouldNotBeIn = new UniqueTagList(tagEconomist, tagPrizeWinner);
-
-        for (Tag tagWhichShouldBeIn : tagsWhichShouldBeIn) {
-            assertTrue(defaultAddressBook.containsTag(tagWhichShouldBeIn));
-        }
-        for (Tag tagWhichShouldNotBeIn : tagsWHichShouldNotBeIn) {
-            assertFalse(defaultAddressBook.containsTag(tagWhichShouldNotBeIn));
-        }
-
-        UniqueTagList allTags = new UniqueTagList(tagPrizeWinner, tagScientist, tagMathematician, tagEconomist);
-
-        for (Tag tag : allTags) {
-            assertFalse(emptyAddressBook.containsTag(tag));
-        }
-    }
-
     @Test
     public void removePerson_personExists_removesNormally() throws Exception {
         int numberOfPersonsBeforeRemoval = getSize(defaultAddressBook.getAllPersons());