Which declare a compilable abstract class? (Choose all that apply.)

technology programming languages

  1. A. public abstract class Canine { public Bark speak(); }

  2. B. public abstract class Canine { public Bark speak() { } }

  3. C. public class Canine { public abstract Bark speak(); }

  4. D. public class Canine abstract { public abstract Bark speak(); }

Show answer
Correct Option: B
Explanation:

To solve this question, the user needs to know the syntax for declaring abstract classes in Java.

Option A: This is not a valid declaration of an abstract class, as it tries to define a method called speak that returns a Bark object, without defining the Bark class or interface. Additionally, it does not declare the class as abstract.

Option B: This is a valid declaration of an abstract class, as it declares the class as abstract using the abstract keyword, and defines an abstract method called speak that returns a Bark object. However, it does not provide an implementation for the method, which makes the class abstract.

Option C: This is not a valid declaration of an abstract class, as it tries to declare an abstract method within a non-abstract class. The class must be declared abstract for it to contain abstract methods.

Option D: This is not a valid declaration of an abstract class, as it tries to declare the class as abstract using the abstract keyword after the class name. The correct syntax is to use abstract before the class name.

Therefore, the correct answers are:

The Answer is: B.

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