Answer: A class that implement an interface must contain methods for all abstract methods in the interface. Otherwise, the class must be declared as abstract.
Step-by-step explanation:
It is necessary to implement all the abstract method that are present in the interface. Basically, this is one of the rule of abstract method. As, abstract method is define as without any implementation.
If any class contain abstract method then, it must be declare as abstract. Therefore, if a class are not implemented an interface method then, it should be declare as abstract.