Interfaces and Abstract Classes -Java Programming MCQ Questions and Answers

1

What is an interface in Java?

A) A contract specifying a set of methods that a class must implement B) A class that cannot be instantiated C) A class that contains only static methods D) A subclass of the Object class

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Answer & Solution

Answer: Option A

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2

In Java, can a class implement multiple interfaces?

A) Interfaces cannot be implemented by classes B) Only abstract classes can implement interfaces C) No, a class can only implement one interface D) Yes, a class can implement multiple interfaces

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Answer & Solution

Answer: Option D

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3

Which keyword is used to declare an interface in Java?

A) class B) abstract C) interface D) extends

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Answer & Solution

Answer: Option C

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4

What is the purpose of an abstract class in Java?

A) To declare abstract methods B) To provide a base class with common methods and fields C) To make a class final D) None of These

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Answer & Solution

Answer: Option B

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5

In Java, can an abstract class be instantiated?

A) Only if it is marked as "final" B) Only if it has a constructor C) No, an abstract class cannot be instantiated D) Yes, an abstract class can be instantiated

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Answer & Solution

Answer: Option C

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6

What is the purpose of the "implements" keyword in Java?

A) To extend an abstract class B) To indicate a constructor C) To create an instance of a class D) To indicate that a class is implementing an interface

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Answer: Option D

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7

Which of the following can contain both abstract and non-abstract methods?

A) Abstract class B) Interface C) Concrete class D) Static class

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Answer & Solution

Answer: Option A

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8

In Java, can an interface have fields (member variables)?

A) Only if they are marked as "static" B) Only if they are marked as "private" C) No, interfaces cannot have fields D) Yes, an interface can have constant (final) fields

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Answer & Solution

Answer: Option D

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9

What is the purpose of an abstract method in an abstract class or interface?

A) To provide a concrete implementation of a method B) To indicate that the method is static C) To declare a method without providing an implementation D) To make the method final

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Answer & Solution

Answer: Option C

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10

Which keyword is used to define an abstract method in Java?

A) void B) abstract C) public D) none of these

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Answer & Solution

Answer: Option B

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