Multiple Choice Questions on JAVA (object oriented programming) bank 6 -- inhertance

MCQs BANK
Page: 1
Object Oriented
Programming
Topic: Inheritance
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MCQs BANK No.: 6

MCQs Bank on Object Oriented Programming
Topic : Inheritance
MCQ No: 1
___________ allows the creation
of hierarchical classifications in
object-oriented programming and
helps to create a general class that
defines traits common to a set of
related items. Fill in the blank.
a) Encapsulation
b) Inheritance
c) Data Hiding
d) Polymorphism
Page: 2

Topic : Inheritance
MCQ No: 1 (Solution)
Ans: b) Inheritance
Explanation: Inheritance allows the
creation of hierarchical classifications in
object-oriented programming. Using
inheritance, you can create a general
class that defines traits common to a set
of related items. This class can then be
inherited by other, more specific classes,
each adding those things that are unique
to it. The idea of inheritance is simple but
powerful: When you want to create a
new class and there is already a class
that includes some of the code that you
want, you can derive your new class
from the existing class. In doing this, you
can reuse the fields and methods of the
existing class without having to write
(and debug!) them yourself..
Page: 3

Topic : Inheritance
MCQ No: 2
In the terminology of Java, a class
that is inherited is called a
___________. Fill in the blank.
a) superclass
b) subclass
c) constructor class
d) destructor class
Page: 4

Topic : Inheritance
Ans: a) superclass
Explanation: In the terminology of
Java, a class that is inherited is
called a superclass. A class that is
derived from another class is
called a subclass (also a derived
class, extended class, or child
class). The class from which the
subclass is derived is called a
superclass (also a base class or a
parent class).
Page: 5

Topic : Inheritance
MCQ No: 3
that does the inheriting is called a
________. Fill in the blank.
a) superclass
b) subclass
c) constructor class
d) destructor class
Page: 6

Topic : Inheritance
Ans: b) subclass
Explanation:
that does the inheriting is called a
subclass. A class that is derived
from another class is called a
subclass (also a derived class,
extended class, or child class). The
class from which the subclass is
derived is called a superclass (also
a base class or a parent class).
Page: 7

Topic : Inheritance
MCQ No: 4
Excepting Object, which has no
superclass, every class has one
and only one direct superclass
(single inheritance). In the absence
of any other explicit superclass,
every class is implicitly a subclass
of Object. True or False
a) True
b) False
Page: 8

Topic : Inheritance
Ans: a) True
Explanation:
Excepting Object, which has no
superclass, every class has one and only
one direct superclass (single inheritance).
In the absence of any other explicit
superclass, every class is implicitly a
subclass of Object.
Classes can be derived from classes that
are derived from classes that are derived
from classes, and so on, and
ultimately derived from the topmost class,
Object. Such a class is said to be
descended from all the classes in the
inheritance chain stretching back to
Object.
Page: 9

Topic : Inheritance
MCQ No: 5
The subclass inherits members of
the superclass and hence
promotes _______. Fill in the
blank.
a) polymorphism
b) code reuse
c) code rewrite
d) multiple inheritance
Page: 10

Topic : Inheritance
Ans: b) code reuse
Explanation:
The subclass inherits members of
the superclass and hence promotes
code reuse. The subclass itself can
add its own new behavior and
properties.
Page: 11

Topic : Inheritance
MCQ No: 6
Private members of the superclass
are not inherited by the subclass.
True or False
a) True
b) False
Page: 12

Topic : Inheritance
Ans: a) True
Explanation:
Private members of the superclass
are not inherited by the subclass
and can only be indirectly
accessed(using public methods).
A subclass inherits all of the public
and protected members of its
parent, no matter what package
the subclass is in.
Page: 13

Topic : Inheritance
MCQ No: 7
A subclass must use the
__________ keyword to derive from
a super class which must be written
in the header of the subclass
definition. Fill in the blank.
a) extends
b) import
c) static
d) super
Page: 14

Topic : Inheritance
Ans: a) extends
Explanation:
A subclass must use the extends
keyword to derive from a super
class which must be written in the
header of the subclass definition.
Page: 15

Topic : Inheritance
MCQ No: 8
Since constructors and initializer
blocks are not members of a class,
they are not inherited by a subclass.
True or False
a) True
b) False
Page: 16

Topic : Inheritance
Ans: a) True
Explanation:
A subclass inherits all the members
(fields, methods, and nested
classes) from its superclass.
Constructors are not members, so
they are not inherited by subclasses,
but the constructor of the superclass
can be invoked from the subclass.
Page: 17

Topic : Inheritance
MCQ No: 9
You can write a subclass
constructor that invokes the
constructor of the superclass,
either implicitly or by using the
keyword ________. Fill in the
blank.
a) default
b) super
c) extends
d) final
Page: 18

Topic : Inheritance
Ans: b) super
Explanation: A parent class
constructor is not inherited in child
class and this is why super() is
added automatically in child class
constructor if there is no explicit call
to super or this.
Page: 19

Topic : Inheritance
MCQ No: 10
You can write a new instance
method in the subclass that has the
same signature as the one in the
superclass, this is called
__________________. Fill in the
blank
a) method calling
b) method overriding
c) method overloading
d) method hiding
Page: 20

Topic : Inheritance
Ans: b) method overriding
Explanation: You can write a new
instance method in the subclass that
has the same signature as the one in
the superclass, thus overriding it. If
subclass (child class) has the same
method as declared in the parent
class, it is known as method
overriding in Java. In other words, If
a subclass provides the specific
implementation of the instance
method that has been declared by
one of its parent class, it is known as
method overriding.
Page: 21

Topic : Inheritance
MCQ No: 11
You can write a new static method
in the subclass that has the same
signature as the one in the
superclass, this is called
_____________. Fill in the blank.
a) method calling
d) method hiding
Page: 22

Topic : Inheritance
Ans: d) method hiding
Explanation:
Method hiding may happen in any
hierarchy structure in java. When a
child class defines a static method
with the same signature as a static
method in the parent class, then the
child's method hides the one in the
parent class.
Page: 23

Topic : Inheritance
MCQ No: 12
You can declare new methods in
the subclass that are not in the
superclass. True or False
a) True
b) False
Page: 24

Topic : Inheritance
Ans: a) True
Explanation:
You can declare new methods in the
subclass that are not in the
superclass. The inherited methods
can be used directly as they are. You
can write a new instance method in
the subclass that has the same
signature as the one in the
superclass, thus overriding it.
Page: 25

Topic : Inheritance
MCQ No: 13
A subclass can call a constructor
defined by its superclass by use of
_________. Fill in the blank.
a) super(parameter-list);
b) super class name
c) constructor(parameter-list);
d) default(parameter-list);
Page: 26

Topic : Inheritance
Ans: a) super(parameter-list);
Explanation:
A subclass can call a constructor
method defined by its superclass by
use of the following form of super:
super(parameter-list);
Here, parameter-list specifies any
parameters needed by the
constructor in the superclass.
super( ) must always be the first
statement executed inside a
subclass’ constructor.
Page: 27

Topic : Inheritance
MCQ No: 14
If we want to refer a member of the
superclass of a subclass, we have
to use _____________. Fill in the
blank.
a) super.member
b) default.member
c) parent.member
d) base-class.member
Page: 28

Topic : Inheritance
Ans: a) super.member
Explanation: The second form of
super acts somewhat like this, except
that it always refers to the superclass
of the subclass in which
it is used. This usage has the
following general form:
super.member
Here, member can be either a method
or an instance variable. This second
form of super is most applicable to
situations in which member names of
a subclass hide members by the
same name in the superclass.
Page: 29

Topic : Inheritance
MCQ No: 15
Which of the following correctly
explains multi-level inheritance.
a) one class extends one class
only
b) the ladder of single inheritance
increases
c) one class directly extends more
than one class
d) none of these
Page: 30

Topic : Inheritance
Ans: b) the ladder of single
inheritance increases
Explanation:
When a class extends a class, which
extends another class then this is
called multilevel inheritance. For
example class C extends class B
and class B extends class A then this
type of inheritance is known as
multilevel inheritance.
Page: 31

Topic : Inheritance
MCQ No: 16
Java supports multiple inheritance
partially through _____________ .
Fill in the blank.
a) inheritance
b) interfaces
c) multiple packages
d) multi-level inheritance
Page: 32

Topic : Inheritance
Ans: b) interfaces
Explanation:
In multiple inheritance, one class
extends multiple classes. Java does
not support multiple inheritance but
C++ supports. Java supports
multiple inheritance partially through
interfaces.
Page: 33

Topic : Inheritance
MCQ No: 17
If one class is extended by many
subclasses, then the type of
inheritance is called __________ .
Fill in the blank.
a) Multi-Level Inheritance
b) Hierarchical Inheritance
c) Multiple Inheritance
d) Single Inheritance
Page: 34

Topic : Inheritance
Ans: b) Hierarchical Inheritance
Explanation: In hierarchical type of
inheritance, one class is extended by many
subclasses. It is one-to-many relationship.
A realtime example is available at dynamic
binding. For example, Bird class is
extended by two classes – Parrot and
Vulture. Both classes can make use of the
methods of Bird. Even though the Parrot
and Vulture are subclasses of the same
class Bird, but still they cannot makeuse of
each other members. Parrot and Vulture
are known as "siblings". Siblings are
disjoint and they cannot make use of other
members as between them no inheritance
is involved (like two sons of a father; one
son's property cannot be shared by other
but both can share the property of father).
Page: 35

Topic : Inheritance
MCQ No: 18
Which of the following are the
disadvantages of Inheritance
a) Both classes (super and
subclasses) are tightly-coupled.
b) As they are tightly coupled
(binded each other strongly with
extends keyword), they cannot
work independently of each other.
c) Changing the code in super
class method also affects the
subclass functionality.
d) All of the above.
Page: 36

Topic : Inheritance
Ans: d) All of the above.
Explanation:
Disadvantages of Inheritance
1. Both classes (super and subclasses)
are tightly-coupled.
2. As they are tightly coupled (binded
each other strongly with extends
keyword), they cannot work independently
of each other.
3. Changing the code in super class
method also affects the subclass
functionality.
4. If super class method is deleted, the
code may not work as subclass may call
the super class method with super
keyword. Now subclass method behaves
independently.
Page: 37

Topic : Inheritance
MCQ No: 19
Defining a method in the subclass
that has the same name, same
arguments and same return type
as a method in the superclass and
it hides the super class method is
called .
a) method rebuilding
d) method calling
Page: 38

Topic : Inheritance
Ans: b) method overriding
Explanation:
Defining a method in the subclass that
has the same name, same arguments
and same return type as a method in
the superclass and it hides the super
class method is called method
overriding. Now when the method is
called, the method defined in the
subclass is invoked and executed
instead of the one in the superclass.
Page: 39

Topic : Inheritance
MCQ No: 20
Method overriding is run time
polymorphism. True or False
a) True
b) False
Page: 40

Topic : Inheritance
Ans: a) True
Explanation:
Defining a method in the subclass
that has the same name, same
arguments and same return type as
a method in the superclass is called
method overriding.
Method overriding is an example of
runtime polymorphism. In method
overriding, a subclass overrides a
method with the same signature as
that of in its superclass. During
compile time, the check is made on
the reference type.
Page: 41

Topic : Inheritance
MCQ No: 21
Method overloading is compile time
polymorphism.
a) True
b) False
Page: 42

Topic : Inheritance
Ans: a) True
Explanation: Overloading a method is
a way to provide more than one method in
one class which have same name but
different argument to distinguish them.
Method overloading is compile time
polymorphism.
Method overloading is the compile-time
polymorphism where more than one
methods share the same name with
different parameters or signature and
different return type. Method overriding is
the runtime polymorphism having same
method with same parameters or
signature, but associated in different
classes.
Page: 43

Topic : Inheritance
MCQ No: 22
_______________ is the
mechanism by which a call to an
overridden method is resolved at
run time, rather than compile time.
Fill in the blank.
a) Dynamic method dispatch
b) Static class select
c) Dynamic class select
d) Static method dispatch
Page: 44

Topic : Inheritance
Ans: a) Dynamic method dispatch
Explanation: Dynamic method dispatch
is the mechanism by which a call to an
overridden method is resolved at run time,
rather than compile time. Dynamic
method dispatch is important because this
is how Java implements run-time
polymorphism.
Overridden method to execution based
upon the type of the object being referred
to at the time the call occurs. Thus, this
determination is made at run time. In
other words, it is the type of the object
being referred to (not the type of the
reference variable) that determines which
version of an overridden method will be
executed.
Page: 45

Multiple Choice Questions on JAVA (object oriented programming) bank 6 -- inhertance

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