18 Questions
What is true about abstract classes in Java?
They can be used as a data type.
What is the main difference between an abstract class and a concrete class?
A concrete class can be instantiated, while an abstract class cannot.
Can a subclass be abstract if its superclass is concrete?
Yes, it can be abstract.
What is an interface primarily used for in Java?
Defining common behavior for classes, including unrelated classes
What is the purpose of constructors in an abstract class?
To be used by subclasses.
Can an abstract class contain abstract methods?
Yes, it can.
What is the relationship between an abstract class and its subclass?
The subclass can be abstract or concrete.
What is a characteristic of an interface in Java?
It can be used as a data type
What is the primary reason for declaring an abstract method in a class?
To declare a method that must be implemented by subclasses.
What happens when a class implements an interface?
The class must provide implementations for all the methods declared in the interface
What can an abstract class contain?
Either abstract methods, concrete methods, or both.
What is the difference between an interface and an abstract class?
An abstract class can have implementation, while an interface cannot
Can an abstract class be instantiated?
No, but it can be subclassed.
What happens if a subclass of an abstract superclass does not implement all the abstract methods?
The subclass is automatically abstract.
What is the difference between an abstract class and a concrete class?
An abstract class cannot be instantiated, while a concrete class can.
What is the purpose of an abstract class?
To provide a blueprint for subclasses.
What is the purpose of defining an interface in Java?
To specify common behavior for objects
What is a key advantage of using interfaces in Java?
It allows for multiple inheritance of behavior
Learn about abstract classes in Java, including their characteristics and limitations. Understand how to use them in inheritance and polymorphism. Discover how to create instances of abstract classes and more.
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