@@ -0,0 +1,292 @@
+package seedu.oneline.commons.exceptions;%0A%0Apublic class StateNonExistentException extends Exception %7B%0A    /**%0A     * @param message should contain relevant information on the failed constraint(s)%0A     */%0A    public StateNonExistentException(String message) %7B%0A        super(message);%0A    %7D%0A%0A%7D%0A

Add StateNonExistentException class