Multiple Choice Questions on JAVA (object oriented programming) bank 5 -- memory management

MCQs BANK
Page: 1
Object Oriented
Programming
Topic: Memory
Management
Instructions:
This MCQs Bank contains question
and solution on adjacent(even-odd)
pages. First try to solve the MCQ by
yourself, then look for the solution.
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MCQs BANK No.: 5

MCQs Bank on Object Oriented Programming
Topic : Memory Management
MCQ No: 1
_____________ is the process of
automatically freeing objects that
are no longer referenced by the
program. Fill in the blank.
a) Polymorphism
b) Data Hiding
c) Garbage collection
d) Encapsulation
Page: 2

MCQ No: 1 (Solution)
Ans: c) Garbage collection
Explanation: The Java virtual machine's
heap stores all objects created by a running
Java application. Objects are created by
the new keyword, but never freed explicitly
by the code. Garbage collection is the
process of automatically freeing objects
that are no longer referenced by the
program.
When an object is no longer referenced by
the program, the heap space it occupies
can be recycled so that the space is made
available for subsequent new objects. The
garbage collector must somehow determine
which objects are no longer referenced by
the program and make available the heap
space occupied by such unreferenced
objects.
Page: 3

MCQ No: 2
____________ occurs through the
course of normal program
execution, new objects are
allocated, and unreferenced
objects are freed such that free
portions of heap memory are left in
between portions occupied by live
objects. Fill in the blank.
a) Garbage Collection
b) Heap fragmentation
c) Encapsulation
d) Polymorphism
Page: 4

Ans: b) Heap fragmentation
Explanation: Heap fragmentation
occurs through the course of normal
program execution. New objects are
allocated, and unreferenced objects are
freed such that free portions of heap
memory are left in between portions
occupied by live objects. Requests to
allocate new objects may have to be
filled by extending the size of the heap
even though there is enough total
unused space in the existing heap. This
will happen if there is not enough
contiguous free heap space available
into which the new object will fit.
Page: 5

MCQ No: 3
Which of the following are the
advantage of garbage collection?
a) Garbage collection relieves you
from the burden of freeing allocated
memory.
b) It can make you more productive.
c) It helps to ensure program
integrity.
d) All of the above.
Page: 6

Ans: d) All of the above
Explanation: Garbage collection relieves
you from the burden of freeing allocated memory.
Knowing when to explicitly free allocated memory
can be very tricky. Giving this job to the Java
virtual machine has several advantages. First, it
can make you more productive. When
programming in non-garbage-collected
languages you can spend many late hours (or
days or weeks) chasing down an elusive memory
problem. When programming in Java you can
use that time more advantageously by getting
ahead of schedule or simply going home to have
a life. A second advantage of garbage collection
is that it helps ensure program integrity. Garbage
collection is an important part of Java's security
strategy. Java programmers are unable to
accidentally (or purposely) crash the Java virtual
machine by incorrectly freeing memory.
Page: 7

MCQ No: 4
What are the disadvantages of a
garbage-collection?
a) it adds an overhead that can
affect program performance.
b) it requires more CPU time
c) programmers have less control
on the memory management
d) all of the above
Page: 8

Ans: d) all of the above
Explanation: A potential disadvantage
of a garbage-collection is that it adds an
overhead that can affect program
performance. The Java virtual machine
has to keep track of which objects are
being referenced by the executing
program, and finalize and free
unreferenced objects on the fly. This
activity will likely require more CPU time
than would have been required if the
program explicitly freed unnecessary
memory. In addition, programmers in a
garbage-collected environment have less
control over the scheduling of CPU time
devoted to freeing objects that are no
longer needed.
Page: 9

MCQ No: 5
Which method is called by the
garbage collector on an object
when garbage collection
determines that there are no more
references to the object?
a) finalize()
b) free()
c) delete()
d) deallocate()
Page: 10

Ans: a) finalize()
Explanation: finalize() is called by the
garbage collector on an object when
garbage collection determines that
there are no more references to the
object. A subclass overrides the finalize
method to dispose of system resources
or to perform other cleanup.
The Finalize method is used to perform
cleanup operations on unmanaged
resources held by the current object
before the object is destroyed. The
method is protected and therefore is
accessible only through this class or
through a derived class.
Page: 11

MCQ No: 6
Which of the following keyword can
be used inside any method to refer
to the current object.
a) this
b) new
c) static
d) final
Page: 12

Ans: a) this
Explanation:
Sometimes a method will need to
refer to the object that invoked it.
To allow this, Java defines the this
keyword. this can be used inside
any method to refer to the current
object.
That is, this is always a reference
to the object on which the method
was invoked. You can use this
anywhere a reference to an object
of the current class' type is
permitted.
Page: 13

MCQ No: 7
If we call a method passing a value,
it is known as call by value and the
changes being done in the called
method, is not affected in the calling
method. True or False?
a) True
b) False
Page: 14

Ans: a) True
Explanation:
There is only call by value in java,
not call by reference(address). If we
call a method passing a value, it is
known as call by value. The
changes being done in the called
method, is not affected in the calling
method.
In case of call by value original
value is not changed.
Page: 15

MCQ No: 8
In case of _____________ original
value is changed if we made
changes in the called method, that
is if we pass object in place of any
primitive value, original value will be
changed. Fill in the blank.
a) call by value
b) call by reference
c) method overloading
d) method overriding
Page: 16

Ans: b) call by reference
Explanation:
In case of call by reference original
value is changed if we made
changes in the called method.
If we pass object in place of any
primitive value, original value will be
changed.
Page: 17

MCQ No: 9
Which of the following modifier
keyword makes that the
programmer cannot change the
value anymore?
a) final
b) static
c) abstract
d) volatile
Page: 18

Ans: a) final
Explanation: The final modifier keyword
makes that the programmer cannot change the
value anymore. The actual meaning depends on
whether it is applied to a class, a variable, or a
method.
final Classes:- A final class cannot have
subclasses. An example:
public final class MathConstants { ... }
This skeleton defines a class called
MathConstants that is publicly accessible but
cannot be subclassed.
Final Variables:-A final variable cannot be
changed once it is initialized.
volatile:-The value of an attribute is not cached
thread-locally, and is always read from the "main
memory"
abstract: -Can only be used in an abstract class,
can only be used on methods. The method does
not have a body, for example abstract void run();.
The body is provided by the subclass (inherited
from).
Page: 19

MCQ No: 10
A ____________ method cannot be
overridden by subclasses. Fill in the
blank.
a) public
b) default
c) final
d) volatile
Page: 20

Ans: c) final
Explanation:
A final method cannot be overridden
by subclasses. There are two
reasons for introducing such a
method:
1. Disallowing subclasses to change
the meaning of the method;
2. Increasing efficiency by allowing
the compiler to turn calls to the
method into inline Java code.
Page: 21

MCQ No: 11
Can we OVERRIDE a static
method?
a) Yes
b) No
c) Unpredictable
d) Machine dependent
Page: 22

Ans: b) No
Explanation:
No, we cannot override static
methods because method
overriding is based on dynamic
binding at runtime and the static
methods are bonded using static
binding at compile time. So, we
cannot override static methods.
Page: 23

MCQ No: 12
Can we OVERLOAD a static
method?
a) Yes
b) No
c) Unpredictable
Page: 24

Ans: a) Yes
Explanation:
The answer is Yes.
We can overload static methods. But
remember that the method signature
must be different.
Page: 25

MCQ No: 13
Can we overload the methods if
they are only different by static
keyword?
a) Yes
b) No
c) Unpredictable
Page: 26

Ans: b) No
Explanation:
The answer is No.
We cannot overload two methods if
they differ only by static keyword. It
give the error: method is already
defined in the class.
Page: 27

MCQ No: 14
A variable or method that is shared
by all instances of a class is called
a class variable or class method.
Such a variable or method in Java
is declared by the _____________
. Fill in the blank.
a) final Keyword
b) static keyword
c) volatile keyword
d) abstract keyword
Page: 28

Ans: b) static keyword
Explanation:
A variable or method that is shared
by all instances of a class is called a
class variable or class method. You
recognize such a variable in Java by
the static keyword in the declaration.
A class variable will instantiate only
one copy of the variable for the
whole class instead of a separate
copy for each instance of a class. A
class variable belongs to a class, not
to an instance of the class.
Page: 29

MCQ No: 15
The Java programming language
allows you to define a class within
another class. Such a class is
called a __________. Fill in the
blank.
a) inside class
b) nested class
c) core class
d) static class
Page: 30

Ans: b) nested class
Explanation: The Java programming
language allows you to define a class
within another class. Such a class is called
a nested class and is illustrated here:
class OuterClass {
...
class NestedClass {
... }
}
A nested class is a member of its enclosing
class. Non-static nested classes (inner
classes) have access to other members of
the enclosing class, even if they are
declared private. Static nested classes do
not have access to other members of the
enclosing class. As a member of the
OuterClass, a nested class can be
declared private, public, protected, or
package private.
Page: 31

MCQ No: 16
Which of the following are the
reasons of using nested classes?
a) It is a way of logically grouping
classes that are only used in one
place.
b) It increases encapsulation.
c) Nested classes can lead to more
readable and maintainable code.
d) All of these.
Page: 32

Ans: d) All of these.
Explanation:
Logical grouping of classes— If a class is
useful to only one other class, then it is logical to
embed it in that class and keep the two together.
Nesting such "helper classes" makes their
package more streamlined.
Increased encapsulation— Consider two top-
level classes, A and B, where B needs access to
members of A that would otherwise be declared
private. By hiding class B within class A, A's
members can be declared private and B can
access them. In addition, B itself can be hidden
from the outside world.
More readable, maintainable code— Nesting
small classes within top-level classes places the
code closer to where it is used.
Page: 33

MCQ No: 17
If you declare an inner class(with a
class name) within the body of a
method. Such a class is known as
a ________________. Fill in the
blank.
a) anonymous inner class.
b) local inner class
c) global inner class.
d) static inner class
Page: 34

Ans: b) local inner class
Explanation:
There are two additional types of
inner classes. You can declare an
inner class within the body of a
method. Such a class is known as a
local inner class. You can also
declare an inner class within the
body of a method without naming
it. These classes are known as
anonymous inner classes.
Page: 35

MCQ No: 18
You can also declare an inner
class within the body of a method
without naming it. Such class is
known as ________________. Fill
in the blank.
a) anonymous inner class.
b) local inner class.
c) global inner class.
d) static inner class
Page: 36

Ans: a) anonymous inner class.
Explanation:
There are two additional types of
inner classes. You can declare an
inner class within the body of a
method. Such a class is known as a
local inner class. You can also
declare an inner class within the
body of a method without naming
it. These classes are known as
anonymous inner classes.
Page: 37

MCQ No: 19
You can use the access specifiers
— private, public, and protected —
to restrict access to inner classes.
True or False
a) True
b) False
Page: 38

Ans: a) True
Explanation: You can use the same
modifiers for inner classes that you use
for other members of the outer class.
For example, you can use the access
specifiers — private, public, and
protected — to restrict access to inner
classes, just as you do to other class
members.
Page: 39

MCQ No: 20
Which of the following statements
are correct?
a) To instantiate an outer class,
you must first instantiate the inner
class.
b) To instantiate an inner class, you
must first instantiate the outer
class.
c) To instantiate an local inner
class, you must first instantiate the
local outer class.
d) To instantiate an anonymous
class, you must first instantiate the
local outer class.
Page: 40

Ans: b) To instantiate an inner class,
you must first instantiate the outer
class.
Explanation:
To instantiate an inner class, you
must first instantiate the outer class.
Then, create the inner object within
the outer object with this syntax:
OuterClass.InnerClass innerObject =
outerObject.new InnerClass(); .
Page: 41

Multiple Choice Questions on JAVA (object oriented programming) bank 5 -- memory management

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