feat: replace PartyException with PartyCityException; update tests accordingly

Author: enyabuti

lesson_16/objects/objects_app/src/main/java/com/codedifferently/lesson16/ezranyabuti/PartyCityException.java

@@ -0,0 +1,7 @@
+package com.codedifferently.lesson16.ezranyabuti;
+
+public class PartyCityException extends Exception {
+  public PartyCityException(String message) {
+    super(message);
+  }
+}

lesson_16/objects/objects_app/src/main/java/com/codedifferently/lesson16/ezranyabuti/partyException.java

@@ -8,7 +8,7 @@ public class PartyExceptionTest {
   @Test
   void testConstructor() {
     String expectedMessage = "Party is not private";
-    PartyException exception = new PartyException(expectedMessage);
+    PartyCityException exception = new PartyCityException(expectedMessage);
     String actualMessage = exception.getMessage();
     assertThat(actualMessage).isEqualTo(expectedMessage);
   }