Question 1

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

Accepted Answer

If Java did not allow you to extend classes, you would not be able to reuse existing code in your program and would need to create every part of the program from scratch. Extending allows a class to inherit the properties and methods of another class, reducing redundancy in code and making it more efficient.

Question 2

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

Accepted Answer

When creating a new subclass in Java, the superclass source code and bytecode are not changed. The subclass simply inherits the properties and methods from the superclass. The object, arguments, and possession of the superclass remain the same.

Question 3

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

Accepted Answer

JAR files compress the data they store, reducing the size of archived class files. Dynamic method bindings is a concept related to runtime polymorphism in object-oriented programming, type-import-on-demand declarations facilitate importing types from packages, and interfaces define a contract for behavior to be implemented by implementing classes.

Question 4

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.

Accepted Answer

An empty method within an abstract class is considered an abstract method, and it is necessary to use the "abstract" keyword to indicate this. Therefore, the answer is C.

Question 5

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

Accepted Answer

When a class overrides the equals() method, it overloads the default equals() method of the Object class.

Question 6

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 ____.

Accepted Answer

When you implement an interface, you must implement all of the methods declared in that interface. If you fail to do so, the class must be declared as abstract. This is because any concrete class that extends the abstract class will be required to implement the unimplemented methods, either directly or through another level of inheritance. Declaring the class as abstract will prevent the compiler errors and allow for the class to be extended later with the missing methods being implemented.

Question 7

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

Accepted Answer

The toString() method is used to display an object's state and can be helpful in debugging a program. It converts the object to a string representation that can be printed or examined in the debugger.

Question 8

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) ____.

Accepted Answer

When you have related classes that inherit from each other and implement multiple interfaces, you should place them in a package. A package is a way of organizing related classes and interfaces in Java. This makes it easier to manage and use the classes in your code. Additionally, placing related classes in a package can help avoid naming conflicts with other classes in your code.

Question 9

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

Accepted Answer

An interface in Java looks much like a class, except that all of its methods (if any) are implicitly public and abstract. It provides a mechanism for specifying a set of related methods that a class can implement, without requiring the class to be a subtype of a particular class. It is commonly used to define a contract for a certain functionality that a class should implement.

Question 10

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

Accepted Answer

A hash code is a calculated number that is used to uniquely identify an object. It is often used in data structures such as hash tables to quickly locate a particular object. Method binding refers to the process of connecting a method call to the appropriate method implementation. Implicit conversion refers to the automatic conversion of one data type to another. Ad-hoc polymorphism refers to the ability of a function or operator to behave differently depending on the data types of its arguments.

Question 11

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

Accepted Answer

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

Question 12

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

Accepted Answer

In class diagrams, abstract classes and methods are typically shown in italics to indicate that they are not concrete implementations but rather templates or placeholders for subclasses to implement. Bold or all caps may be used for emphasis, but italics are the standard convention for abstract elements in UML. Blue is not a standard color for indicating abstractness in class diagrams.

Question 13

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

Accepted Answer

The Object class equals() method returns a boolean value indicating whether the objects are equal or not. It returns true if the objects are equal, and false otherwise. Therefore, the best choice for the answer is D.

Question 14

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

Accepted Answer

By convention, when a class both extends another class and implements interfaces, the extends clause comes first, followed by the implements clause in the class header.

Question 15

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

Accepted Answer

If no package is specified for a class, it is placed in the default package.

Question 16

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 ____.

Accepted Answer

The equals() method of the Object class considers two objects to be equal only if they have the same hash code.

Question 17

Which of the following is NOT true regarding abstract methods?

Accepted Answer

Abstract methods are not inherited by child classes. Child classes must implement or override the abstract method.

Question 18

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

Accepted Answer

In C++, abstract classes are known as virtual classes. They contain at least one pure virtual function and cannot be instantiated, only used as a base class for other derived classes.

Question 19

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

Accepted Answer

The method that returns an integer representing the hash code is named hashCode() and it belongs to the Object class in Java. Therefore, the best choice is B.

Question 20

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

Accepted Answer

Packages and class libraries in Java are often delivered to users as JAR (Java ARchive) files, which contain compiled Java code along with necessary metadata and resources. This makes it easier for developers to distribute and manage their code, as well as for users to integrate it into their own projects. The other options, such as interface, .java file, or class file, are all components of Java programming, but they do not serve the same purpose as a JAR file.

Quiz 11: Advanced Inheritance Concepts