Chapter 6: Class design Flashcards
Override happens in runtime and can be used do polymorphism in runtime.
True
Overload altera a assinatura do método e ocorre dentro da mesma classe.
Verdadeiro
Override pode ser usado em métodos construtores.
Falso
Overload permite o uso de diferentes assinaturas para métodos com o mesmo nome e pode ser aplicado em métodos construtores.
Verdadeiro
Override ocorre dentro da mesma classe e requer alteração de assinatura.
Falso
True or False: In Java 17, a method inside an abstract class must be marked as abstract if it does not have a method body. If false, why?
True
An abstract class in Java 17 can contain both abstract and non-abstract methods. If false, why?
True
A non-abstract method inside an abstract class must have a method body in Java 17. If false, why?
True
Java 17 allows abstract classes to define methods without a body, even if they are not marked abstract. If false, why?
False: A method without a body must be marked abstract.
If an abstract method is declared inside an abstract class in Java 17, it must be implemented by its first concrete subclass. If false, why?
True
True or False: In Java 17, a subclass automatically includes all members of the superclass, including private members. If false, why?
False: Private members are not inherited; they are only accessible within the superclass.
A subclass in Java 17 must always explicitly declare the extends keyword to inherit from a superclass. If false, why?
True
A superclass in Java 17 cannot be marked final if it is meant to be inherited. If false, why?
True
In Java 17, a subclass can inherit both instance variables and methods from its superclass. If false, why?
True
Inheritance in Java 17 is not transitive, meaning a subclass does not inherit from its grandparent class. If false, why?
False: Inheritance is transitive; a subclass indirectly inherits from all ancestor classes.
A class can extend multiple classes in Java 17 using multiple extends keywords. If false, why?
False: Java does not support multiple inheritance with classes; a class can extend only one superclass.
Protected members of a superclass are accessible in the subclass even if they are in different packages. If false, why?
True
If a superclass and subclass are in the same package, the subclass can access package-private (default) members. If false, why?
True
The term “supertype” in Java 17 applies only to classes, not interfaces. If false, why?
False: “Supertype” applies to both classes and interfaces.
Private members of a superclass can never be accessed in a subclass, even through methods of the superclass. If false, why?
False: A subclass can access private members indirectly through public or protected methods of the superclass.
What is Liskov Substitution Principle and Type Safety?
The rule exists to ensure that objects of a subclass can be used wherever objects of the superclass (or interface) are expected — without breaking access expectations.
Can an overridden method have more restrictive access than the method in the superclass or interface?
No, an overridden method cannot have more restrictive access than the original method. It must be at least as accessible.
What happens if a subclass tries to override a public method from its superclass with a protected or private method?
A compile-time error occurs because the overridden method must maintain or increase visibility, not reduce it.
In object-oriented programming, what determines which overridden method is called at runtime?
The actual type of the object, not the reference type, determines which overridden method is executed.
If a method is overridden in a subclass, what happens when the method is called on a reference of a superclass type?
The subclass’s version of the method is executed, thanks to polymorphism and dynamic method dispatch.
Why does calling a method on a base type reference sometimes produce output from a subclass implementation?
Because the method is overridden in the subclass, and the object at runtime belongs to the subclass, not the base class.
