Computer science JAVA multiple choice questions Question 16 Which of the followi

Question

Computer science JAVA multiple choice questions

Question 16

Which of the following can contain a constructor?

Question 16 options:

Any abstract class or interface

Any nonabstract or abstract class

Any class or interface

Any nonabstract class or interface

Question 17

What is the output the program shown below.

interface A

{

}

class D extends C

{

}

class C

{

}

class B extends D implements A

{

}

public class Quiz2F

{

    public static void main(String[] args)

    {

        B b = new B();

        if (b instanceof A)

            System.out.println("b is an instance of A");

        if (b instanceof C)

            System.out.println("b is an instance of C");

    }

}

Question 17 options:

b is an instance of A

Nothing

b is an instance of C

b is an instance of A followed by b is an instance of C

Question 18

Which of the following class definitions defines a legal abstract class?

Question 18 options:

abstract class A { abstract void unfinished(); }

public class abstract A { abstract void unfinished(); }

class A { abstract void unfinished(); }

class A { abstract void unfinished() {     } }

Question 19

Which of the following statements regarding abstract methods is not true?

Question 19 options:

Abstract classes can have constructors

It is possible to declare an abstract class that contains no abstract methods

A data field can be declared abstract

A class that contains abstract methods must be abstract

Question 20

What is true about using the reserved word super?

Question 20 options:

It can only be used in a class that contains an extends clause

It can only be used in a constructor

It can only be used in subclasses

It can only be used in superclasses

Explanation / Answer

Question 16)

Therefore the correct option is “Any non-abstract or abstract class”.

Question 17)

Therefore the correct option is “b is an instance of A followed by b is an instance of C”.

Question 18)

abstract class CLASSNAME{

//declarations of data and non-abstract methods

//declarations of abstract methods

Therefore the correct option is “abstract class A {abstract void unfinished(); }”.

Question 19)

Therefore the correct option is “A data field can be declared abstract”.

Question 20)

Therefore the correct option is “It can only be used in subclasses”.

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