12. Can an object be a subclass of another object? A. Yes-as long as single inheritance is followed. B. No inheritance is only between classes. C. Only when one has been defined in terms of the other. D. Yes when one object is used in the constructor of another. 13. What is an abstract class? A. An abstract class is one without any child classes. B. An abstract class is any parent class with more than one child class. C. An abstract class is class which cannot be instantiated. D. abstract class is another name for "base class." 14. Can an abstract class define both abstract methods and non-abstract methods? A. No it must have all one or the other. B. No-it must have all abstract methods. C. Yes but the child classes do not inherit the abstract methods. D. Yes the child classes inherit both.

Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
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20:38
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12. Can an object be a subclass of another object?
A. Yes as long as single inheritance is followed.
B. No inheritance is only between classes.
C. Only when one has been defined in terms of the other.
D. Yes when one object is used in the constructor of another.
13. What is an abstract class?
A. An abstract class is one without any child classes.
B. An abstract class is any parent class with more than one child class.
C.
An abstract class is class which cannot be instantiated.
D.
abstract class is another name for "base class."
14. Can an abstract class define both abstract methods and non-abstract methods?
A.
No it must have all one or the other.
B.
No it must have all abstract methods.
C.
Yes but the child classes do not inherit the abstract methods.
D.
Yes the child classes inherit both.
15. Can an abstract method be defined in a non-abstract class?
A. No-if a class defines an abstract method the class itself must be abstract.
B. No only classes are abstract, not methods.
C.
Yes-a method can be declared abstract in any parent as long as the child classes
also declare it abstract.
Yes there is no restriction on where abstract methods can be defined.
D.
16. What is polymorphism in Java?
A.
It is when a single variable is used with several different types of related objects at
different places in a program.
B. It is when a program uses several different types of objects, each with its own
variable.
C.
It is when a single parent class has many child classes.
D.
It is when a class has several methods with the same name but different parameter
types.
17. Given the method declaration below,
public void m1 (int num1, int num2) {}
which method declaration override method m1 when written in a subclass?
A. public void m2 (int numl, int num2) ()
B. public void m1 (int num1, double num2) ()
C. public string ml (int num1, int num2, int num3) ()
D. public int ml (int numl, int num2) ()
LTE
18. When a class implements an interface, what must it do?
A. It must redefine each constant from the interface.
B. It must declare and provide a method body for each method in the interface.
C. It must declare a variable for each constant in the interface.
D. It must include a private method for each method in the interface.
19. What is the base class of nearly all Swing classes?
a
Transcribed Image Text:20:38 Back adjava300 18-Nov-2022 11-46-... 12. Can an object be a subclass of another object? A. Yes as long as single inheritance is followed. B. No inheritance is only between classes. C. Only when one has been defined in terms of the other. D. Yes when one object is used in the constructor of another. 13. What is an abstract class? A. An abstract class is one without any child classes. B. An abstract class is any parent class with more than one child class. C. An abstract class is class which cannot be instantiated. D. abstract class is another name for "base class." 14. Can an abstract class define both abstract methods and non-abstract methods? A. No it must have all one or the other. B. No it must have all abstract methods. C. Yes but the child classes do not inherit the abstract methods. D. Yes the child classes inherit both. 15. Can an abstract method be defined in a non-abstract class? A. No-if a class defines an abstract method the class itself must be abstract. B. No only classes are abstract, not methods. C. Yes-a method can be declared abstract in any parent as long as the child classes also declare it abstract. Yes there is no restriction on where abstract methods can be defined. D. 16. What is polymorphism in Java? A. It is when a single variable is used with several different types of related objects at different places in a program. B. It is when a program uses several different types of objects, each with its own variable. C. It is when a single parent class has many child classes. D. It is when a class has several methods with the same name but different parameter types. 17. Given the method declaration below, public void m1 (int num1, int num2) {} which method declaration override method m1 when written in a subclass? A. public void m2 (int numl, int num2) () B. public void m1 (int num1, double num2) () C. public string ml (int num1, int num2, int num3) () D. public int ml (int numl, int num2) () LTE 18. When a class implements an interface, what must it do? A. It must redefine each constant from the interface. B. It must declare and provide a method body for each method in the interface. C. It must declare a variable for each constant in the interface. D. It must include a private method for each method in the interface. 19. What is the base class of nearly all Swing classes? a
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