Question 1

Consider the following code snippet:
Public interface Sizable
{
Int LARGE_CHANGE = 100;
Void changeSize();
}
Which of the following indicates how to use the constant LARGE_CHANGE in your program?
A) LARGE_CHANGE
B) Sizable.LARGE_CHANGE
C) Sizable(LARGE_CHANGE)
D) You cannot directly use the LARGE_CHANGE constant in your program.

Accepted Answer

The constant LARGE_CHANGE is declared within the Sizable interface, so it can only be accessed using the interface name and dot operator. The correct way to use the constant is by referencing it as Sizable.LARGE_CHANGE.

Question 2

Consider the following code snippet:
Public class Inventory implements Measurable
{
Private int onHandCount;
) . .
Public double getMeasure();
{
Return onHandCount;
}
}
Why is it necessary to declare getMeasure as public?
A) All methods in a class are not public by default.
B) All methods in an interface are private by default.
C) It is necessary only to allow other classes to use this method.
D) It is not necessary to declare this method as public.

Accepted Answer

By default, methods in a class are not public, so it is necessary to declare the getMeasure method as public to make it accessible to other classes. Option B is incorrect because methods in an interface are public by default. Option C is partially correct but does not provide a complete explanation. Option D is incorrect because it is necessary to declare the method as public.

Question 3

To define a class that fulfills the requirements of an interface, the class header should include which of the following?
A) The keyword extends and the name of an abstract method in the interface
B) The keyword extends and the name of the interface
C) The keyword implements and the name of an abstract method in the interface
D) The keyword implements and the name of the interface

Accepted Answer

To define a class that fulfills the requirements of an interface, the class header should include the keyword implements and the name of the interface. Option A is incorrect because the keyword extends is used for inheritance of a class, not for implementing an interface. Option B is also incorrect because it is not possible to extend an interface. Option C is incorrect because the keyword implements should only be followed by the name of the interface, not an abstract method within the interface.

Question 4

To test whether an object belongs to a particular type, use ___.
A) the this reserved word.
B) the subclassOf reserved word.
C) the instanceof operator.
D) the equals method.

Accepted Answer

The instanceof operator is used to test whether an object belongs to a particular type. It returns true if the object is an instance of the specified type, and false otherwise. The other options mentioned are not used specifically for this purpose.

Question 5

You are creating a Motorcycle class which is supposed to use an interface named Measurable. Which of the following class declaration statements will accomplish this?
A) public class Motorcycle inherits Measurable
B) public class Motorcycle implements Measurable
C) public class Motorcycle interfaces Measurable
D) public class Motorcycle extends Measurable

Accepted Answer

The correct syntax for implementing an interface in a class is to use the keyword "implements" followed by the name of the interface. Therefore, option B is the correct choice. Option A is incorrect because the keyword "inherits" is not used in Java for inheritance. Option C is incorrect because the keyword "interfaces" is not used in Java for implementing interfaces. Option D is incorrect because the keyword "extends" is used for inheritance of classes, not interfaces.

Question 6

Which statement about methods in an interface is true?
A) All methods in an interface are automatically private.
B) All methods in an interface are automatically public.
C) All methods in an interface are automatically static.
D) All methods in an interface must be explicitly declared as private or public.

Accepted Answer

In Java, all methods in an interface are automatically public. This is because the purpose of an interface is to define a contract or a set of behaviors that must be implemented by any class that implements the interface. Therefore, all methods defined within an interface must be accessible to any implementing class.

Question 7

Which of the following could be used in place of an interface to handle operations on different classes?
A) Function objects
B) Operator overloading
C) Dynamic method lookup
D) Abstract classes

Accepted Answer

The answer of Which of the following could be used...

Question 8

Consider the following code snippet:
Public interface Sizable
{
Int LARGE_CHANGE = 100;
Int SMALL_CHANGE = 20;
Void changeSize();
}
Which of the following statements is true?
A) LARGE_CHANGE and SMALL_CHANGE are automatically public static final.
B) LARGE_CHANGE and SMALL_CHANGE are instance variables.
C) LARGE_CHANGE and SMALL_CHANGE must be defined with the keywords private static final.
D) LARGE_CHANGE and SMALL_CHANGE must be defined with the keywords public static final.

Accepted Answer

In an interface, all variables are implicitly public, static, and final, so LARGE_CHANGE and SMALL_CHANGE are automatically public static final.

Question 9

Consider the following code snippet: Public class BankAccount implements Comparable { . . . Public int compareTo(T other) { What is wrong with this code? A) The type parameter for the Comparable interface in the implements clause must be the same as the implementing class. B) The type parameter for the Comparable interface in the implements clause must be the generic . C) The type parameter for the compareTo method must be the same as the implementing class. D) The type parameter for the compareTo interface must be the generic .

Accepted Answer

The answer of Consider the following code snippet:
Public class BankAccount...

Question 10

Consider the following code snippet:
Public class Inventory implements Measurable
Which of the following statements about this code is correct?
A) The Inventory class is an interface, while the Measurable class is a concrete class.
B) The Measurable class is an interface, while the Inventory class is a concrete class.
C) The Inventory class is an abstract class, while the Measurable class is a concrete class.
D) The Inventory class is a subclass, while the Measurable class is a superclass.

Accepted Answer

The code snippet shows that the Inventory class is implementing the Measurable interface. Therefore, the Measurable class must be an interface while the Inventory class is a concrete class that is implementing the Measurable interface.

Question 11

Which of the following can potentially be changed when implementing an interface?
A) The parameters of a method defined by the interface.
B) The name of a method defined by the interface.
C) The return type of a method defined by the interface.
D) You cannot change the name, return type, or parameters of a method defined by the interface.

Accepted Answer

When implementing an interface, you must adhere to the method signatures defined by the interface, which includes the method name, parameters, and return type. These cannot be changed.

Question 12

Consider the following code snippet:
Public class Inventory implements Measurable
{
Private int onHandCount;
) . .
Double getMeasure();
{
Return onHandCount;
}
}
If getMeasure() is a method in the interface Measurable, what is wrong with this code?
A) The getMeasure method must be declared as private.
B) The getMeasure method must include the implements keyword.
C) The getMeasure method must be declared as public.
D) The getMeasure method must not have any code within it.

Accepted Answer

The getMeasure method must be declared as public in order to implement the Measurable interface. In addition, there is an extra ")" after the onHandCount field declaration that should not be there.

Question 13

Which of the following statements about an interface is true?
A) An interface has methods and instance variables.
B) An interface has methods but no instance variables.
C) An interface has neither methods nor instance variables.
D) An interface has instance variables but no methods.

Accepted Answer

An interface only has method signatures (methods without implementation) and no instance variables. The purpose of an interface is to provide a contract for classes to implement its methods.

Question 14

All ____ methods must be implemented when using an interface.
A) abstract.
B) private.
C) public.
D) static

Accepted Answer

Interface methods are by default abstract, which means they do not have an implementation within the interface and must be implemented by any class that implements the interface.

Question 15

Which of the following statements about a Java interface is NOT true?
A) A Java interface defines a set of methods that are required.
B) A Java interface must contain more than one method.
C) A Java interface specifies behavior that a class will implement.
D) All methods in a Java interface must be abstract.

Accepted Answer

A Java interface can contain only one method or multiple methods. There are no restrictions on the number of methods in an interface.

Question 16

Consider the following code snippet:
Public class Inventory implements Measurable
{
Private int onHandCount;
) . .
Double getMeasure();
{
Return onHandCount;
}
}
Assume that getMeasure() is a method in the interface Measurable. The compiler complains that the getMeasure method has a weaker access level than the Measurable interface. Why?
A) All of the methods in a class have a default access level of package access, while the methods of an interface have a default access level of private.
B) All of the methods in a class have a default access level of package access, while the methods of an interface have a default access level of public.
C) The variable onHandCount was not declared with public access.
D) The getMeasure method was declared as private in the Measurable interface.

Accepted Answer

In Java, all methods in a class have a default access level of package access, which means they are only accessible within the same package. However, all methods in an interface have a default access level of public, which means they can be accessed from any package. Since the getMeasure method in the Inventory class is attempting to implement the Measurable interface, it must also have a public access level, which is stronger than the default package access level. Therefore, changing the access level of the getMeasure method from default to public will resolve the compiler error.

Question 17

You are creating a Vessel class which is supposed to use an interface named Measurable. Which of the following class declaration statements will accomplish this?
A) public class Vessel inherits Measurable
B) public class Vessel implements Measurable
C) public class Vessel interfaces Measurable
D) public class Vessel extends Measurable

Accepted Answer

To use an interface in a class, we need to implement that interface. So, the correct way to use the Measurable interface in the Vessel class is by using the keyword "implements". Option A and D use the keywords "inherits" and "extends" respectively, which are not valid for implementing an interface. Option C uses the keyword "interfaces", which is not a valid keyword in Java.

Question 18

Consider the following code snippet:
Public interface Sizable
{
Double size;
Double getSize();
}
What is wrong with this code?
A) The getSize method must be declared as public.
B) the getSize method must be declared as public.
C) The getSize method must be declared as final.
D) An interface type cannot have instance variables.

Accepted Answer

An interface type cannot have instance variables. It is incorrect to declare a variable like 'Double size' within an interface. Instead, we should declare only the method signature using the abstract keyword. Thus, the correct interface declaration should be:

public interface Sizable {
  Double getSize();
}

Question 19

A method that has no implementation is called a/an ____ method.
A) interface
B) implementation
C) overloaded
D) abstract

Accepted Answer

An abstract method is a method that has no implementation and is marked with the abstract keyword. It is used in abstract classes or interfaces where the subclass or implementing class is responsible for providing the implementation of the method.

Quiz 9: Inheritance and Interfaces

Consider the following code snippet: Public interface Sizable { Int LARGE_CHANGE = 100; Void changeSize() ; } Which of the following indicates how to use the constant LARGE_CHANGE in your program?

Consider the following code snippet: Public class Inventory implements Measurable { Private int onHandCount; ) . . Public double getMeasure() ; { Return onHandCount; } } Why is it necessary to declare getMeasure as public?

To define a class that fulfills the requirements of an interface, the class header should include which of the following?

To test whether an object belongs to a particular type, use ___.

You are creating a Motorcycle class which is supposed to use an interface named Measurable. Which of the following class declaration statements will accomplish this?

Which statement about methods in an interface is true?

Which of the following could be used in place of an interface to handle operations on different classes?

Consider the following code snippet: Public interface Sizable { Int LARGE_CHANGE = 100; Int SMALL_CHANGE = 20; Void changeSize() ; } Which of the following statements is true?

Consider the following code snippet: Public class BankAccount implements Comparable<BankAccount> { . . . Public int compareTo(T other) { What is wrong with this code?

Consider the following code snippet: Public class Inventory implements Measurable Which of the following statements about this code is correct?

Which of the following can potentially be changed when implementing an interface?

Consider the following code snippet: Public class Inventory implements Measurable { Private int onHandCount; ) . . Double getMeasure() ; { Return onHandCount; } } If getMeasure() is a method in the interface Measurable, what is wrong with this code?

Which of the following statements about an interface is true?

All ____ methods must be implemented when using an interface.

Which of the following statements about a Java interface is NOT true?

You are creating a Vessel class which is supposed to use an interface named Measurable. Which of the following class declaration statements will accomplish this?

Consider the following code snippet: Public interface Sizable { Double size; Double getSize() ; } What is wrong with this code?

A method that has no implementation is called a/an ____ method.