Change APIException interface into class

src/main/java/nl/utwente/ing/exception/APIException.java

@@ -1,11 +1,19 @@
 package nl.utwente.ing.exception;
 
 /**
- * The APIException interface.
- * Used as the parent of all APIExceptions.
+ * The APIException class.
+ * Extends Exception.
+ * Used as the superclass of all APIExceptions.
  *
  * @author Daan Kooij
  */
-public interface APIException {
+public class APIException extends Exception {
+
+    /**
+     * The empty constructor of APIException.
+     */
+    public APIException() {
+
+    }
 
 }

src/main/java/nl/utwente/ing/exception/InvalidSessionIDException.java

@@ -2,12 +2,12 @@
 
 /**
  * The InvalidSessionIDException class.
- * Extends Exception and implements APIException.
+ * Extends APIException.
  * InvalidSessionIDException is thrown whenever a sessionID is missing or invalid.
  *
  * @author Daan Kooij
  */
-public class InvalidSessionIDException extends Exception implements APIException {
+public class InvalidSessionIDException extends APIException {
 
     /**
      * The empty constructor of InvalidSessionIDException.

src/main/java/nl/utwente/ing/exception/ResourceNotFoundException.java

@@ -2,12 +2,12 @@
 
 /**
  * The ResourceNotFoundException class.
- * Extends Exception and implements APIException.
+ * Extends APIException.
  * ResourceNotFoundException is thrown whenever a resource is not found.
  *
  * @author Daan Kooij
  */
-public class ResourceNotFoundException extends Exception implements APIException {
+public class ResourceNotFoundException extends APIException {
 
     /**
      * The empty constructor of ResourceNotFoundException.