Classes, objects and encapsulation: Practice Questions

• a.

  Polymorphism

• b.

  Encapsulation

• c.

  Inheritance

• d.

  Instantiation

• a.The variable is accessible only within the class it is defined and cannot be seen by subclasses.
• b.The variable is accessible within its own class, any subclasses (even in different packages), and other classes in the same package.
• c.The variable is accessible by all classes within the entire application regardless of their package or inheritance relationship.
• d.The variable can be accessed by subclasses only if they are defined within the same package as the parent class.

• a.Because interfaces automatically implement all methods, reducing the workload for the programmer.
• b.Because interfaces increase the coupling between classes, making the code more robust.
• c.To avoid the 'Diamond Problem' where ambiguity arises if two parent classes provide different implementations of the same method.
• d.Because interfaces allow for the inheritance of state (instance variables) while concrete classes do not.

• a.

  To destroy an object when it is no longer needed.

• b.

  To initialize the state of an object when it is created.

• c.

  To prevent external classes from accessing private data.

• d.

  To allow a subclass to inherit methods from a superclass.

• a.

  A weak relationship where the child object can exist independently of the parent.

• b.

  That one class is an interface implemented by the other.

• c.

  A strong ownership where the child object cannot exist without the parent.

• d.

  That the classes share a parent-child inheritance relationship.

Write your answer out first, then check it against the worked solution.

Write your answer out first, then check it against the worked solution.

Write your answer out first, then check it against the worked solution.

Write your answer out first, then check it against the worked solution.

Write your answer out first, then check it against the worked solution.