Deck 11: Advanced Inheritance Concepts

Question 1

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 1

A

Question 2

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

Answer 2

B

Question 3

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

Answer 3

True

Question 4

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

Question 5

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 6

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

Question 7

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

Question 8

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

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

Question 9

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

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

Question 10

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

Question 11

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 12

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

Question 13

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

Question 14

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

Question 15

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 16

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

Question 17

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 18

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

Question 19

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

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

Question 20

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

Question 21

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 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

____ 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 24

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.

A) virtual
B) implements
C) abstract
D) extends

Question 25

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 26

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)   new

Question 27

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 28

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) ____.

A) group
B) package
C) abstract class
D) file

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

____ 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 31

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

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

Question 32

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

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

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

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

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

Question 35

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 36

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 ____.

A) address
B) value
C) hash code
D) number of characters

Question 37

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 38

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

A) anonymous
B) pseudo
C) simulated
D) virtual

Question 39

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 40

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

A) JAR
B) interface
C) .java
D) class

Question 41

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

Question 42

A functional interface ____.

A) is the same as a package
B) can have multiple lambda expressions
C) contains just one abstract method
D) can only contain  effectively final variables

Question 45

What is dynamic method binding and why is it used?

Question 50

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

Question 53

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

Question 61

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

Question 62

Compare and contrast abstract classes and interfaces.

Question 63

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

Question 64

How is the Object class equals() method implemented?

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

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

Question 67

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

Question 68

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 69

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

Question 70

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 71

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 72

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 73

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

Question 74

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 75

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 76

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 77

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.

Question 78

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