Deck 11: Advanced Inheritance Concepts

Question 1

Classes from which objects can be instantiated are called constant classes.

Answer 1

False

Question 2

When you assign a variable or constant of one type to a variable of another type, the behavior is called ____.

A) implicit conversion
B) referencing
C) dynamic method binding
D) containing

Answer 2

A

Question 3

When you define a class, if you do not explicitly extend another class, your class is an extension of the ____ class.

A) Object
B) super
C) public
D) abstract

Answer 3

A

Question 4

An application's ability to select the correct subclass method is known as ____.

A) implementing methods
B) dynamic method binding
C) implicit casting
D) method fixing

Question 5

If you create an empty method within an abstract class, the method is abstract even if you do not explicitly use the keyword abstract.

Question 6

You sometimes create an abstract class only so you can ____ it to another class.

A) link
B) copy
C) extend
D) abstract

Question 7

Abstract classes and interfaces are similar in that you cannot instantiate concrete objects from either one.

Question 8

When you create a superclass and one or more subclasses, each object of each subclass is a subclass object.

Question 9

A(n) ____ class is a class that you create only to extend from.

A) abstract
B) inheritance
C) parent
D) final

Question 10

The Object class ____ method converts an Object into a String that contains information about the Object .

A) equals()
B) setType()
C) toString()
D) speak()

Question 11

The java.lang package contains fundamental classes and is imported automatically each time a program is written.

Question 12

A(n) ____ is not an object, but it points to a memory address.

A) abstract class
B) reference
C) extend
D) interface

Question 13

A class that will be placed in a nondefault package for others to use must be private .

Question 14

If you attempt to instantiate an object from an abstract class, you receive an error message from the compiler that you have committed a(n) ____.

A) LogicError
B) InstantiationError
C) SyntaxError
D) ObjectError

Question 15

When you create a class that uses an interface, you include the keyword extends .

Question 16

Instead of using the automatic toString() method with your classes, it is usually more useful to write your own ____ version of the toString() method that displays some or all of the data field values for the object with which you use it.

A) overloaded
B) protected
C) static
D) condensed

Question 17

While a class can inherit from multiple abstract superclasses, it implement only one interface.

Question 18

It is common to create an interface when you want a class to implement behavior from more than one parent.

Question 19

Which of the following statements creates an array of three Animal references?

A) Animal[] ref = new Animal(3);
B) Animal[] new = ref Animal[3];
C) Animal[] animalRef = new Animal[3];
D) Animal[] ref = extend Animal[3];

Question 20

Java does not allow a class to inherit directly from two or more parents.

Question 21

When you show abstract classes and methods in class diagrams, their names appear in ____.

A) bold
B) all caps
C) italics
D) blue

Question 22

When you create a new subclass in Java, neither the superclass source code nor the superclass ____ is changed.

A) bytecode
B) object
C) argument
D) possession

Question 23

Classes, such as the String class, have their own equals() methods that overload the ____ class method.

A) Object
B) Public
C) Abstract
D) Child

Question 24

Which of the following is NOT true regarding abstract methods?

A) Abstract methods must be implemented in child classes.
B) Abstract methods have no body.
C) Abstract methods use the abstract keyword in declarations.
D) Abstract methods are inherited by their children.

Question 25

When you create a class and use the implements clause to implement an interface but fail to code one of the interface's methods, the compiler error generated indicates that you must declare your class to be ____.

A) abstract
B) static
C) public
D) related

Question 26

If Java did not allow you to ____ classes, you would need to create every part of a program from scratch.

A) extend
B) override
C) abstract
D) import

Question 27

The Object class equals() method returns a boolean value indicating whether the objects are equal. This equals() method considers two objects to be equal only if they have the same ____________________ .

Question 28

If you provide an empty method within an abstract class, the method is an abstract method even if you do not explicitly use the keyword ____________________ when defining the method.

Question 29

A(n) ____ looks much like a class, except that all of its methods (if any) are implicitly public and abstract.

A) hash code
B) package
C) collision
D) interface

Question 30

If you do not specify a package for a class, it is placed in an unnamed ____ package.

A) system
B) language
C) default
D) general

Question 31

____ compress the data they store, which reduces the size of archived class files.

A) Dynamic method bindings
B) JAR files
C) Type-import-on-demand declarations
D) Interfaces

Question 32

When you create a number of classes that inherit from each other, as well as multiple interfaces that you want to implement with these classes, you often will find it convenient to place these related classes in a(n) ____________________.

Question 33

The Object class equals() method returns a(n) ____ value indicating whether the objects are equal.

A) int
B) equals
C) null
D) boolean

Question 34

In other programming languages, such as C++, abstract classes are known as ____________________ classes.

Question 35

The capability to inherit from more than one class is called ____.

A) multiple inheritance
B) collision
C) polyinheritance
D) dynamic method binding

Question 36

In the Java programming language, a package or class library is often delivered to users as a(n) ____________________ file.

Question 37

The ____ method is useful in debugging a program because it can be used to display and examine values.

A) finalize()
B) toString()
C) notify()
D) equals()

Question 38

Java's Object class contains a public method named ____ that returns an integer representing the hash code.

A) length()
B) hashCode()
C) hcode()
D) toString()

Question 39

____ is a calculated number that is used to uniquely identify an object.

A) Method binding
B) A hash code
C) Implicit conversion
D) Ad-hoc polymorphism

Question 40

When a class both extends and implements, by convention the ____ clause follows the extends clause in the class header.

A) extends
B) new
C) implements
D) if

Question 42

public interface FindTheError
{
    void firstMethod(int anIntNum)
   {
        System.out.println("Did you find the error?");
   }
}
What is the problem with the above interface? How would you correct the interface?

Question 43

Why do many programmers consider multiple inheritance to be a difficult concept?

Question 44

public class CarReference
{
    public static void main(String[] args)
    {
       Car carRef;
       ----Code here---
       carRef.color();
    }
}
Suppose you have created a Car class and Honda and Ford subclasses. Using the above code, complete the indicated statement to create a new Honda object that is assigned to the Car reference.

Question 45

When you create classes for others to use, why would you not want to provide the users with your source code in the files with .java extensions?

Question 46

Describe the two method types programmers of an abstract class can include.

Question 47

When a superclass is abstract, you cannot instantiate objects of a superclass. How can you use a superclass abstract object?

Question 48

Compare and contrast abstract classes and interfaces.

Question 49

The equals() method returns a boolean value indicating whether two objects are equal. Using the above code, will the two BankAccount objects be equal? Explain why or why not.

Question 50

public class Animal
{
}
public class Animal extends Object
{
}
The two class declarations above have identical outcomes. Explains why this is the case.

Question 51

What is the toString() method used for and how is it used?

Question 52

What is an abstract class? Give an example and explain how it works.

Question 53

How is the Object class equals() method implemented?

Question 54

Give an example of how you can create an interface to have a class implement behavior from more than one parent.

Question 55

What are the advantages to creating a useful, extendable superclass?

Question 56

What is dynamic method binding and why is it used?

Question 57

The AnimalReference application shown above contains a generic Animal reference variable into which you can assign concrete Animal objects. Explain how this example uses polymorphism and why it is important.

Question 58

public abstract class Car
{
    private String model;
    public abstract void color();
    public String getName()
    {
        return model;
     }
     public void setName(String carModel)
     {
        model = carModel;
      }
}
Using the code above, would it be possible to create a class in which you declare a Car object with the statement Car myCar = new Car("Honda"); ?
Explain why or why not.

Question 59

public abstract class Car
{
    private String model;
    public abstract void color();
    public String getModel()
    {
         return model;
     }
    public void setModel(String modelName)
    {
         model = modelName;
     }
}
public class Honda extends Car
{
    public void color()
    {
System.out.println("red");
    }
}
public class Ford extends Car
{
    public void color()
    {
      System.out.println("blue");
    }
}
public class MyCars
{
    public static void main(String[] args)
    {
       Honda myHonda = new Honda();
       Ford myFord = new Ford();
  myHonda.setModel("My Honda is ");
       myFord.setModel("My Ford is ");
  System.out.print(myHonda.getModel());
  myHonda.color();
  System.out.print(myFord.getModel());
  myFord.color();
    }
}
In the above code, the myHonda.getModel() and myHonda.color() method calls produce different output from when the same methods are used with myFord . Explain why this is the case.

Question 60

When you create a useful, extendable superclass, you and other future programmers gain what advantages?

Question 61

An array can be created to reserve space for references to objects. Using the code above, explain how an array of superclass references can hold subclass references.

Question 62

The shaded header of the talkingAnimal() method accepts any type of Animal argument. Explain how this is possible.

Question 63

public abstract class Car
{
    private String model;
    public abstract void color();
    public String getModel()
    {
         return model;
    }
    public void setModel(String modelName)
    {
         model = modelName;
    }
}
public class Honda extends Car
{
    public void color()
    {
       System.out.println("red");
    }
}
public class Ford extends Car
{
    public void color()
    {
      System.out.println("blue");
    }
}
public class MyCars
{
    public static void main(String[] args)
    {
       Honda myHonda = new Honda();
       Ford myFord = new Ford();
       myHonda.setModel("My Honda is ");
       myFord.setModel("My Ford is ");
       System.out.print(myHonda.getModel());
       myHonda.color();
       System.out.print(myFord.getModel());
       myFord.color();
    }
}
Using the above code, describe the output that will appear when the program is executed.

Question 64

public abstract class Car
{
    private String model;
    public abstract void color();
    public String getModel()
    {
         return model;
    }
    public void setModel(String modelName)
    {
         model = modelName;
    }
}
The above code creates a generic abstract class named Car with an abstract color() method. Using the code below, fill in the indicated statements in order to create a Honda class that extends Car .
public class --Code here-- extends --Code here--
{
    public void --Code here--
    {
       System.out.println("I like your red car!");
    }
}

Question 65

The code above provides an example of an interface class. Explain the purpose and advantages of creating interfaces that store related constants.

Question 66

public abstract class Shape
{
    private int length;
    private int width;
    private int height;
    ----Code here----
}
Using the above code, create the statement in the place indicated that will create an abstract calculateArea() method in the abstract Shape class.