Question 1

The method that must be implemented in a class using the Comparable interface is:
(a)public Object compareTo(Object other)
(b)public Boolean compareTo(Object other)
(c)public int compareTo(Object other)
(d)none of the above

C

Accepted Answer

The correct method signature to implement in a class using the Comparable interface is public int compareTo(Object other), which takes an Object as a parameter and returns an integer. This method is used to compare the current object with the specified object and it should return a negative integer if the current object is less than the specified object, zero if they are equal, and a positive integer if the current object is greater than the specified object. Option A is incorrect because it returns an Object instead of an integer, while option B is incorrect because it returns a Boolean instead of an integer. Option D is incorrect because at least one of the options A, B, and C must be implemented to use the Comparable interface.

Question 2

A class that uses an interface must use the keyword:&#10;(a)Extends&#10;(b)Inherits&#10;(c)Super&#10;(d)Implements

Accepted Answer

When a class wants to implement the methods defined in an interface, it must use the keyword "implements" followed by the interface name. The keyword "extends" is used to inherit from a superclass, while "super" is used to call a constructor or method of a superclass. "Inherits" is not a keyword in Java.

Question 3

If an inner class contains non static members,then the class name must be modified by the keyword:&#10;(a)Final&#10;(b)Static&#10;(c)Void&#10;(d)Protected

Accepted Answer

The keyword "static" must be added to the inner class name if it contains non-static members. This is because an inner class can only be instantiated within an instance of the outer class, but non-static members are associated with instances of the inner class itself rather than the outer class. By making the inner class static, its members are associated with the outer class itself and can be accessed without first instantiating an instance of the inner class.

Question 4

The Comparable interface is in the ______________ package.&#10;(a)java.util&#10;(b)java.io&#10;(c)java.awt&#10;(d)java.lang

Accepted Answer

The Comparable interface is part of the java.lang package, which contains fundamental classes and interfaces closely tied to the language.

Question 5

A Java interface is an example of:&#10;(a)encapsulation&#10;(b)abstraction&#10;(c)polymorphism&#10;(d)all of the above

Accepted Answer

A Java interface is an example of abstraction, as it provides a way to define a set of method signatures without providing any implementation details. While interfaces also contribute to encapsulation and polymorphism in Java, they are primarily used for abstraction.

Question 6

A class that implements an interface but only gives definitions for some of the method headings given in the interface is called a/an:
(a)concrete class
(b)abstract class
(c)discrete class
(d)friendly class

Accepted Answer

A class that implements an interface but only gives definitions for some of the method headings given in the interface is called an abstract class. An interface has a set of method headings, but it doesn't have any implementation. When a class implements an interface, it is required to define all of the method headings specified in the interface. However, an abstract class that implements an interface doesn't have to define all of the methods in the interface but can leave some of them abstract.

Question 7

Inner classes available outside the scope of their outer class are modified by the keyword:&#10;(a)Public&#10;(b)Private&#10;(c)Protected&#10;(d)Package access

Accepted Answer

Inner classes are by default private and can only be accessed within the outer class. To access the inner class outside the scope of its outer class, it needs to be modified with the keyword public, making it accessible to other classes. Protected or package access would restrict access to the inner class.

Question 8

Any constant variables defined in an interface must be defined as:&#10;(a)public&#10;(b)private&#10;(c)protected&#10;(d)package access

Accepted Answer

Any constant variable defined in an interface must be defined as public as it needs to be accessible to the implementing class. Private, protected, or package access fields cannot be accessed by the implementing class.

Question 9

Java interfaces are a way of simulating multiple inheritance.

Accepted Answer

Java interfaces allow a class to inherit methods and constants from multiple interfaces, similar to multiple inheritance. However, unlike multiple inheritance, a class can implement multiple interfaces without inheriting implementation details from them.

Question 10

An interface specifies the headings and definitions for methods that must be defined in any class that implements the interface.

Accepted Answer

An interface specifies the headings (signatures) for methods, but it does not provide the definitions. The implementing class is responsible for providing the definitions for these methods.

Question 11

When defining an inner class to be a helper class for an outer class,the inner classes access should be marked as:&#10;(a)Public&#10;(b)Private&#10;(c)Protected&#10;(d)Package access

Accepted Answer

The answer of When defining an inner class to be...

Question 12

A class may only implement one interface.

Accepted Answer

The answer of A class may only implement one interface....

Question 13

An interface may contain:&#10;(a)instance variables&#10;(b)primitive variables&#10;(c)constant variables&#10;(d)all of the above

Accepted Answer

The answer of An interface may contain:&#10;(a)instance variables&#10;(b)primitive variables&#10;(c)constant variables&#10;(d)all...

Question 14

An interface is a type.

Accepted Answer

The answer of An interface is a type....

Question 15

When using the clone method from an inherited base class you should account for a _________ exception.
(a)CloneNotFoundException
(b)CloneEmptyException
(c)CloneNotSupportedException
(d)CloneNotEmptyException

Accepted Answer

The answer of When using the clone method from an...

Question 16

You can not derive an interface from a base interface.

Accepted Answer

The answer of You can not derive an interface from...

Question 17

An interface and all of its method headings are normally declared to be:&#10;(a)public&#10;(b)private&#10;(c)protected&#10;(d)package access

Accepted Answer

The answer of An interface and all of its method...

Question 18

The compareTo method should return _____________ if the calling object equals the parameter.&#10;(a)A negative number&#10;(b)Zero&#10;(c)A positive number&#10;(d)Null

Accepted Answer

The answer of The compareTo method should return _____________ if...

Question 19

In Java,a derived class can have ________ base class(es).&#10;(a)one&#10;(b)two&#10;(c)three&#10;(d)there is no limit

Accepted Answer

The answer of In Java,a derived class can have ________...

Question 20

A common use of inner classes is :&#10;(a)clean up&#10;(b)set up&#10;(c)helper&#10;(d)all of the above

Accepted Answer

The answer of A common use of inner classes is...

Question 21

What are the semantics of the Comparable interface?

Accepted Answer

The answer of What are the semantics of the Comparable...

Question 22

Java source code that contains a class with an inner class,when compiled,will produce a separate .class file for the inner class.

Accepted Answer

The answer of Java source code that contains a class...

Question 23

An interface can contain defined constants as well as method headings or instead of method headings.

Accepted Answer

The answer of An interface can contain defined constants as...

Question 24

An inner class definition is local to the outer class definition.

Accepted Answer

The answer of An inner class definition is local to...

Question 25

The compiler and the run-time system enforces semantics on the Comparable interface.

Accepted Answer

The answer of The compiler and the run-time system enforces...

Question 26

What are the obligations of a class that implements a specific interface?

Accepted Answer

The answer of What are the obligations of a class...

Question 27

Inner and outer classes do not have access to each other's private members.

Accepted Answer

The answer of Inner and outer classes do not have...

Question 28

What are two advantages to using inner classes?

Accepted Answer

The answer of What are two advantages to using inner...

Question 29

What is an anonymous class?

Accepted Answer

The answer of What is an anonymous class?...

Question 30

The Serializable interface is like all the other Java interfaces in that it contains defined constants and method headings.

Accepted Answer

The answer of The Serializable interface is like all the...

Question 31

What are the rules of total ordering?

Accepted Answer

The answer of What are the rules of total ordering?...

Question 32

Why does Java only allow the inheritance of only one base class?

Accepted Answer

The answer of Why does Java only allow the inheritance...

Deck 13: Interfaces and Inner Classes