Question 1

Which of the following statements about inheritance is correct?

Accepted Answer

A)  You can always use a superclass object in place of a subclass object. 
B)  You can always use a subclass object in place of a superclass object. 
C)  A superclass inherits data and behavior from a subclass. 
D)  A superclass inherits only behavior from a subclass. 
A)  You can always use a superclass object in place of a subclass object. 
B)  You can always use a subclass object in place of a superclass object. 
C)  A superclass inherits data and behavior from a subclass. 
D)  A superclass inherits only behavior from a subclass.

Question 2

Consider the following code snippet:
Vehicle aVehicle = new Auto();
AVehicle.moveForward(200);
If the Auto class inherits from the Vehicle class, and both classes have an implementation of the moveForward method with the same set of parameters and the same return type, which statement is correct?

Accepted Answer

A)  The moveForward method of the Auto class will be executed. 
B)  The moveForward method of the Vehicle class will be executed. 
C)  You must specify in the code which class's moveForward method is to be used. 
D)  It is not possible to determine which class's method is called. 
A)  The moveForward method of the Auto class will be executed. 
B)  The moveForward method of the Vehicle class will be executed. 
C)  You must specify in the code which class's moveForward method is to be used. 
D)  It is not possible to determine which class's method is called.

Question 3

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?

Accepted Answer

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. 
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.

Question 4

Consider the following code snippet:
Auto consumerAuto = new Auto(4, "gasoline");
String s = consumerAuto.toString();
Assume that the Auto class has not implemented its own toString() method. What value will s contain when this code is executed?

Accepted Answer

A)  s will contain the values of the instance variables in consumerAuto. 
B)  s will contain only the name of the consumerAuto object. 
C)  s will contain the name of the consumerAuto object followed by a hash code. 
D)  This code will not compile. 
A)  s will contain the values of the instance variables in consumerAuto. 
B)  s will contain only the name of the consumerAuto object. 
C)  s will contain the name of the consumerAuto object followed by a hash code. 
D)  This code will not compile.

Question 5

Consider the following code snippet:
Public class Vessel
{
) . .
Public void setVesselClass(double numberAxles)
{
) . .
}
}
Public class Speedboat extends Vessel
{
) . .
Public void setVesselClass(double numberAxles)
{
) . .
}
}
Which of the following statements is correct?

Accepted Answer

A)  The Speedboat class overrides the setVesselClass method. 
B)  The Vessel class overrides the setVesselClass method. 
C)  The Speedboat class overloads the setVesselClass method. 
D)  The Vessel class overloads the setVesselClass method. 
A)  The Speedboat class overrides the setVesselClass method. 
B)  The Vessel class overrides the setVesselClass method. 
C)  The Speedboat class overloads the setVesselClass method. 
D)  The Vessel class overloads the setVesselClass method.

Question 6

Consider the following code snippet:
Public class Motorcycle extends Vehicle
{
) . .
Public Motorcycle(int numberAxles)
{
Super(numberAxles); //line #1
}
}
If the line marked "//line #1" was missing, which of these statements would be correct?

Accepted Answer

A)  The Motorcycle class constructor would invoke the constructor of the Vehicle class with no parameters. 
B)  The Vehicle class constructor would invoke the constructor of the Motorcycle class with no parameters. 
C)  The Motorcycle class constructor would invoke the constructor of the Vehicle class with a parameter value of 0. 
D)  This code would not compile. 
A)  The Motorcycle class constructor would invoke the constructor of the Vehicle class with no parameters. 
B)  The Vehicle class constructor would invoke the constructor of the Motorcycle class with no parameters. 
C)  The Motorcycle class constructor would invoke the constructor of the Vehicle class with a parameter value of 0. 
D)  This code would not compile.

Question 7

Consider the following code snippet:
Public class Vehicle
{
) . .
Public void setVehicleClass(double numberAxles)
{
) . .
}
}
Public class Motorcycle extends Vehicle
{
) . .
Public void setModelName(String model)
{
) . .
}
Public void setVehicleClass(double numberAxles)
{
) . .
}
}
Which of the following statements is NOT correct?

Accepted Answer

A)  The Motorcycle class can call the setVehicleClass method of the Vehicle class. 
B)  The Vehicle class can call the setModelName method. 
C)  The Motorcycle class overrides the setVehicleClass method. 
D)  The Motorcycle class can call the setVehicleClass method of the Motorcycle class. 
A)  The Motorcycle class can call the setVehicleClass method of the Vehicle class. 
B)  The Vehicle class can call the setModelName method. 
C)  The Motorcycle class overrides the setVehicleClass method. 
D)  The Motorcycle class can call the setVehicleClass method of the Motorcycle class.

Question 8

Which of the following statements about classes is true?

Accepted Answer

A)  You can create an object from a concrete class, but not from an abstract class. 
B)  You can create an object from an abstract class, but not from a concrete class. 
C)  You cannot have an object reference whose type is an abstract class. 
D)  You cannot create subclasses from abstract classes. 
A)  You can create an object from a concrete class, but not from an abstract class. 
B)  You can create an object from an abstract class, but not from a concrete class. 
C)  You cannot have an object reference whose type is an abstract class. 
D)  You cannot create subclasses from abstract classes.

Question 9

Consider the following code snippet:
Double salary = 45000.00;
String sal = "Current salary is " + salary;
Which of the following statements is correct?

Accepted Answer

A)  The toString method of the Object class is being used to set the value of sal. 
B)  The toString method of the Double class is being used to set the value of sal. 
C)  No toString method is being used to set the value of sal. 
D)  This code will not compile. 
A)  The toString method of the Object class is being used to set the value of sal. 
B)  The toString method of the Double class is being used to set the value of sal. 
C)  No toString method is being used to set the value of sal. 
D)  This code will not compile.

Question 10

Which of the following is true regarding subclasses?

Accepted Answer

A)  A subclass inherits methods from its superclass but not instance variables. 
B)  A subclass inherits instance variables from its superclass but not methods. 
C)  A subclass inherits methods and instance variables from its superclass. 
D)  A subclass does not inherit methods or instance variables from its superclass. 
A)  A subclass inherits methods from its superclass but not instance variables. 
B)  A subclass inherits instance variables from its superclass but not methods. 
C)  A subclass inherits methods and instance variables from its superclass. 
D)  A subclass does not inherit methods or instance variables from its superclass.

Question 11

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

Accepted Answer

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. 
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.

Question 12

All ____ methods must be implemented when using an interface.

Accepted Answer

A)  abstract. 
B)  private. 
C)  public. 
D)  static 
A)  abstract. 
B)  private. 
C)  public. 
D)  static

Question 13

Consider the following code snippet:
Public class Auto extends Vehicle
{
) . .
Public Auto(int numberAxles)
{
Super(numberAxles);
}
}
What does this code do?

Accepted Answer

A)  It invokes the constructor of the Vehicle class from within the constructor of the Auto class. 
B)  It invokes the constructor of the Auto class from within the constructor of the Vehicle class. 
C)  It invokes a private method of the Vehicle class from within a method of the Auto class. 
D)  This code will not compile. 
A)  It invokes the constructor of the Vehicle class from within the constructor of the Auto class. 
B)  It invokes the constructor of the Auto class from within the constructor of the Vehicle class. 
C)  It invokes a private method of the Vehicle class from within a method of the Auto class. 
D)  This code will not compile.

Question 14

Which of the following statements about comparing objects is correct?

Accepted Answer

A)  The equals method is used to compare whether two references are to the same object. 
B)  The equals method is used to compare whether two objects have the same contents. 
C)  The == operator is used to compare whether two objects have the same contents. 
D)  The equals method and the == operator are perform the same actions. 
A)  The equals method is used to compare whether two references are to the same object. 
B)  The equals method is used to compare whether two objects have the same contents. 
C)  The == operator is used to compare whether two objects have the same contents. 
D)  The equals method and the == operator are perform the same actions.

Question 15

Consider the following inheritance hierarchy diagram:   Which of the following statements is correct?

Accepted Answer

A)  Auto is a superclass of LandVehicle, and LandVehicle is a superclass of Vehicle. 
B)  Auto is a superclass of LandVehicle, and LandVehicle is a subclass of Vehicle. 
C)  Auto is a subclass of LandVehicle, and LandVehicle is a superclass of Vehicle. 
D)  Auto is a subclass of LandVehicle, and LandVehicle is a subclass of Vehicle. 
A)  Auto is a superclass of LandVehicle, and LandVehicle is a superclass of Vehicle. 
B)  Auto is a superclass of LandVehicle, and LandVehicle is a subclass of Vehicle. 
C)  Auto is a subclass of LandVehicle, and LandVehicle is a superclass of Vehicle. 
D)  Auto is a subclass of LandVehicle, and LandVehicle is a subclass of Vehicle.

Question 16

Consider the following code snippet:
Public class Motorcycle extends Vehicle
{
Private String model;
) . .
Public Motorcycle(int numberAxles, String modelName)
{
Super(numberAxles);
Model = modelName;
}
}
What does this code do?

Accepted Answer

A)  It invokes the constructor of the Vehicle class from within the constructor of the Motorcycle class. 
B)  It invokes the constructor of the Motorcycle class from within the constructor of the Vehicle class. 
C)  It invokes a private method of the Vehicle class from within a method of the Motorcycle class. 
D)  This code will not compile. 
A)  It invokes the constructor of the Vehicle class from within the constructor of the Motorcycle class. 
B)  It invokes the constructor of the Motorcycle class from within the constructor of the Vehicle class. 
C)  It invokes a private method of the Vehicle class from within a method of the Motorcycle class. 
D)  This code will not compile.

Question 17

Which of the following statements about superclasses and subclasses is true?

Accepted Answer

A)  A superclass is larger than its subclass. 
B)  A superclass inherits from a subclass. 
C)  A superclass extends a subclass. 
D)  A subclass extends a superclass. 
A)  A superclass is larger than its subclass. 
B)  A superclass inherits from a subclass. 
C)  A superclass extends a subclass. 
D)  A subclass extends a superclass.

Question 18

Consider the following code snippet of a function object
Public interface Measurer
{
Double measure(______ anObject);
}
Complete this code to allow the interface to handle all classes?

Accepted Answer

A)  Class 
B)  Object 
C)  Any 
D)  Void 
A)  Class 
B)  Object 
C)  Any 
D)  Void

Question 19

Which of the following indicates that a class named ClassA class is a superclass of the ClassB class?

Accepted Answer

A)  public class ClassB extends ClassA 
B)  public class ClassB implements ClassA 
C)  public class ClassA extends ClassB 
D)  public class ClassA implements ClassB 
A)  public class ClassB extends ClassA 
B)  public class ClassB implements ClassA 
C)  public class ClassA extends ClassB 
D)  public class ClassA implements ClassB

Question 20

Consider the following code snippet:
Public abstract class Machine
{
Public abstract void setRPMs();
) . .
}
You wish to create a subclass named PolisherMachine. Which of the following is the correct way to declare this subclass?

Accepted Answer

A)  public class PolisherMachine implements Machine
{
Public void setRPMs() { . . . }
} 
B)  public class PolisherMachine extends Machine
{
Void setRPMs() { . . . }
} 
C)  public class PolisherMachine implements Machine
{
Void setRPMs() { . . . }
} 
D)  public class PolisherMachine extends Machine
{
Public void setRPMs() { . . . }
} 
A)  public class PolisherMachine implements Machine
{
Public void setRPMs() { . . . }
} 
B)  public class PolisherMachine extends Machine
{
Void setRPMs() { . . . }
} 
C)  public class PolisherMachine implements Machine
{
Void setRPMs() { . . . }
} 
D)  public class PolisherMachine extends Machine
{
Public void setRPMs() { . . . }
}

Exam 9: Inheritance and Interfaces

Which of the following statements about inheritance is correct?

Consider the following code snippet: Vehicle aVehicle = new Auto(); AVehicle.moveForward(200); If the Auto class inherits from the Vehicle class, and both classes have an implementation of the moveForward method with the same set of parameters and the same return type, which statement is correct?

Consider the following code snippet: Auto consumerAuto = new Auto(4, "gasoline"); String s = consumerAuto.toString(); Assume that the Auto class has not implemented its own toString() method. What value will s contain when this code is executed?

Consider the following code snippet: Public class Vessel { ) . . Public void setVesselClass(double numberAxles) { ) . . } } Public class Speedboat extends Vessel { ) . . Public void setVesselClass(double numberAxles) { ) . . } } Which of the following statements is correct?

Consider the following code snippet: Public class Motorcycle extends Vehicle { ) . . Public Motorcycle(int numberAxles) { Super(numberAxles); //line #1 } } If the line marked "//line #1" was missing, which of these statements would be correct?

Which of the following statements about classes is true?

Consider the following code snippet: Double salary = 45000.00; String sal = "Current salary is " + salary; Which of the following statements is correct?

Which of the following is true regarding subclasses?

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

All ____ methods must be implemented when using an interface.

Consider the following code snippet: Public class Auto extends Vehicle { ) . . Public Auto(int numberAxles) { Super(numberAxles); } } What does this code do?

Which of the following statements about comparing objects is correct?

Consider the following inheritance hierarchy diagram: Which of the following statements is correct?

Consider the following code snippet: Public class Motorcycle extends Vehicle { Private String model; ) . . Public Motorcycle(int numberAxles, String modelName) { Super(numberAxles); Model = modelName; } } What does this code do?

Which of the following statements about superclasses and subclasses is true?

Consider the following code snippet of a function object Public interface Measurer { Double measure(______ anObject); } Complete this code to allow the interface to handle all classes?

Which of the following indicates that a class named ClassA class is a superclass of the ClassB class?

Consider the following code snippet: Public abstract class Machine { Public abstract void setRPMs(); ) . . } You wish to create a subclass named PolisherMachine. Which of the following is the correct way to declare this subclass?

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