JavaInterviewQuestions-UdemyCourse-September2016.pdf

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Java Interview Questions and Answers
– www.in28Minutes.com
1
www.in28minutes.com
Java Interview
Questions and
Answers
2
Java Interview Questions and Answers
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Java Interview Companion - Books & Videos
Copyright © 2016 by in28Minutes
All rights reserved. No part of this work may be reproduced or transmitted in
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symbol with every occurrence of a trademarked name, we use the names only
in an editorial fashion and to the benefit of the trademark owner, with no
intention of infringement of the trademark.
Java and all Java-based marks are trademarks or registered trademarks of Sun
Microsystems, Inc. in the US and other countries.
In28Minutes is not affiliated with Sun Microsystems, Inc., and this book was
written without endorsement from Sun Microsystems, Inc.
Lead Editor: Ranga Karanam
For information on translations, please contact Ranga at
http://www.in28minutes.com
The information in this book is distributed on an “as is” basis, without
warranty. Although every precaution has been taken in the preparation of this
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The source code for this book is available to readers at
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Java Interview Questions and Answers
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TABLE OF CONTENTS
3
JAVA PLATFORM ................................................................................................................................ 10
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
W
HY IS
J
AVA SO
P
OPULAR
? ................................................................................................... 10
W
HAT IS
P
LATFORM
I
NDEPENDENCE
? ..................................................................................... 10
W
HAT IS
B
YTE
C
ODE
? ........................................................................................................... 11
C
OMPARE
JDK
VS
JVM
VS
JRE. ............................................................................................ 11
.
W
HAT ARE THE IMPORTANT DIFFERENCES BETWEEN
C++
AND
J
AVA
? ........................................... 12
.
W
HAT IS THE ROLE FOR A
C
LASS
L
OADER IN
J
AVA
? ..................................................................... 12
W
HAT ARE WRAPPER CLASSES
? .............................................................................................. 14
W
HY DO WE NEED
W
RAPPER
C
LASSES IN
J
AVA
? ....................................................................... 14
.
W
HAT ARE THE DIFFERENT WAYS OF CREATING
W
RAPPER
C
LASS
I
NSTANCES
? ................................ 14
W
HAT ARE DIFFERENCES IN THE TWO WAYS OF CREATING
W
RAPPER
C
LASSES
? ............................... 15
W
HAT IS
A
UTO
B
OXING
? ...................................................................................................... 16
W
HAT ARE THE ADVANTAGES OF
A
UTO
B
OXING
? ...................................................................... 16
W
HAT IS
C
ASTING
? .............................................................................................................. 16
W
HAT IS
I
MPLICIT
C
ASTING
? ................................................................................................. 16
W
HAT IS
E
XPLICIT
C
ASTING
? ................................................................................................. 17
.
A
RE ALL
S
TRING
’
S IMMUTABLE
? ............................................................................................. 18
W
HERE ARE STRING VALUES STORED IN MEMORY
? .................................................................... 18
.
W
HY SHOULD YOU BE CAREFUL ABOUT
S
TRING
C
ONCATENATION
(+)
OPERATOR IN
L
OOPS
? .............. 18
H
OW DO YOU SOLVE ABOVE PROBLEM
? ................................................................................... 19
W
HAT ARE DIFFERENCES BETWEEN
S
TRING AND
S
TRING
B
UFFER
? ................................................. 19
W
HAT ARE DIFFERENCES BETWEEN
S
TRING
B
UILDER AND
S
TRING
B
UFFER
? ..................................... 19
C
AN YOU GIVE EXAMPLES OF DIFFERENT UTILITY METHODS IN
S
TRING CLASS
? ................................. 19
W
HAT IS A
C
LASS
? ............................................................................................................... 21
W
HAT IS AN
O
BJECT
? ........................................................................................................... 21
W
HAT IS STATE OF AN
O
BJECT
? .............................................................................................. 21
W
HAT IS BEHAVIOR OF AN
O
BJECT
? ........................................................................................ 22
W
HAT IS THE SUPER CLASS OF EVERY CLASS IN
J
AVA
? ................................................................. 22
E
XPLAIN ABOUT TO
S
TRING METHOD
? ..................................................................................... 22
W
HAT IS THE USE OF EQUALS METHOD IN
J
AVA
? ....................................................................... 23
W
HAT ARE THE IMPORTANT THINGS TO CONSIDER WHEN IMPLEMENTING EQUALS METHOD
? ............ 24
W
HAT IS THE HASH
C
ODE METHOD USED FOR IN
J
AVA
? ............................................................... 25
E
XPLAIN INHERITANCE WITH
E
XAMPLES
. .................................................................................. 25
WRAPPER CLASSES ............................................................................................................................. 14
STRINGS ............................................................................................................................................. 18
OBJECT ORIENTED PROGRAMMING BASICS ....................................................................................... 21
4
Java Interview Questions and Answers
– www.in28Minutes.com
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
W
HAT IS
M
ETHOD
O
VERLOADING
? ........................................................................................ 26
W
HAT IS
M
ETHOD
O
VERRIDING
? ........................................................................................... 27
C
AN SUPER CLASS REFERENCE VARIABLE CAN HOLD AN OBJECT OF SUB CLASS
? ................................ 27
I
S
M
ULTIPLE
I
NHERITANCE ALLOWED IN
J
AVA
? ......................................................................... 28
.
W
HAT IS AN
I
NTERFACE
? ...................................................................................................... 28
.
H
OW DO YOU DEFINE AN
I
NTERFACE
? ..................................................................................... 28
H
OW DO YOU IMPLEMENT AN INTERFACE
? ............................................................................... 29
C
AN YOU EXPLAIN A FEW TRICKY THINGS ABOUT INTERFACES
? ..................................................... 29
C
AN YOU EXTEND AN INTERFACE
? ........................................................................................... 30
C
AN A CLASS EXTEND MULTIPLE INTERFACES
? ........................................................................... 30
W
HAT IS AN
A
BSTRACT
C
LASS
? .............................................................................................. 31
W
HEN DO YOU USE AN
A
BSTRACT
C
LASS
? ................................................................................ 31
H
OW DO YOU DEFINE AN ABSTRACT METHOD
? ......................................................................... 31
.
C
OMPARE
A
BSTRACT
C
LASS VS
I
NTERFACE
? ............................................................................. 32
W
HAT IS A
C
ONSTRUCTOR
? ................................................................................................... 32
W
HAT IS A
D
EFAULT
C
ONSTRUCTOR
? ...................................................................................... 32
W
ILL THIS CODE COMPILE
? .................................................................................................... 33
H
OW DO YOU CALL A
S
UPER
C
LASS
C
ONSTRUCTOR FROM A
C
ONSTRUCTOR
? ................................. 33
W
ILL THIS CODE
C
OMPILE
? ................................................................................................... 33
.
W
HAT IS THE USE OF THIS
()? ................................................................................................. 33
C
AN A CONSTRUCTOR BE CALLED DIRECTLY FROM A METHOD
? ..................................................... 34
I
S A SUPER CLASS CONSTRUCTOR CALLED EVEN WHEN THERE IS NO EXPLICIT CALL FROM A SUB CLASS
CONSTRUCTOR
? .................................................................................................................. 34
.
W
HAT IS
P
OLYMORPHISM
? ................................................................................................... 35
W
HAT IS THE USE OF INSTANCEOF
O
PERATOR IN
J
AVA
? .............................................................. 36
W
HAT IS
C
OUPLING
? ........................................................................................................... 37
.
W
HAT IS
C
OHESION
? ........................................................................................................... 38
.
W
HAT IS
E
NCAPSULATION
? ................................................................................................... 39
W
HAT IS AN
I
NNER
C
LASS
? .................................................................................................... 41
W
HAT IS A
S
TATIC
I
NNER
C
LASS
? ........................................................................................... 41
.
C
AN YOU CREATE AN INNER CLASS INSIDE A METHOD
? ................................................................ 41
W
HAT IS AN
A
NONYMOUS
C
LASS
? ......................................................................................... 41
W
HAT IS DEFAULT CLASS MODIFIER
? ....................................................................................... 43
W
HAT IS PRIVATE ACCESS MODIFIER
? ...................................................................................... 43
W
HAT IS DEFAULT OR PACKAGE ACCESS MODIFIER
? ................................................................... 43
W
HAT IS PROTECTED ACCESS MODIFIER
? ................................................................................. 43
.
W
HAT IS PUBLIC ACCESS MODIFIER
? ........................................................................................ 44
ADVANCED OBJECT ORIENTED CONCEPTS .......................................................................................... 35
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
MODIFIERS ........................................................................................................................................ 43
.
Java Interview Questions and Answers
– www.in28Minutes.com
5
69.
70.
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
81.
82.
83.
84.
85.
86.
87.
88.
89.
90.
91.
92.
93.
94.
95.
96.
97.
98.
99.
100.
101.
102.
W
HAT ACCESS TYPES OF VARIABLES CAN BE ACCESSED FROM A
C
LASS IN
S
AME
P
ACKAGE
? ................ 44
W
HAT ACCESS TYPES OF VARIABLES CAN BE ACCESSED FROM A
C
LASS IN
D
IFFERENT
P
ACKAGE
? ......... 44
W
HAT ACCESS TYPES OF VARIABLES CAN BE ACCESSED FROM A
S
UB
C
LASS IN
S
AME
P
ACKAGE
? ......... 45
W
HAT ACCESS TYPES OF VARIABLES CAN BE ACCESSED FROM A
S
UB
C
LASS IN
D
IFFERENT
P
ACKAGE
? .. 45
.
W
HAT IS THE USE OF A FINAL MODIFIER ON A CLASS
? ................................................................. 46
W
HAT IS THE USE OF A FINAL MODIFIER ON A METHOD
? ............................................................. 46
W
HAT IS A
F
INAL VARIABLE
? .................................................................................................. 46
W
HAT IS A FINAL ARGUMENT
? ............................................................................................... 47
W
HAT HAPPENS WHEN A VARIABLE IS MARKED AS VOLATILE
? ...................................................... 47
W
HAT IS A
S
TATIC
V
ARIABLE
? ................................................................................................ 47
W
HY SHOULD YOU ALWAYS USE BLOCKS AROUND IF STATEMENT
? ................................................ 49
G
UESS THE OUTPUT
............................................................................................................. 49
.
G
UESS THE OUTPUT
............................................................................................................. 49
.
G
UESS THE OUTPUT OF THIS SWITCH BLOCK
. ............................................................................. 49
G
UESS THE OUTPUT OF THIS SWITCH BLOCK
? ............................................................................ 50
S
HOULD DEFAULT BE THE LAST CASE IN A SWITCH STATEMENT
? .................................................... 50
C
AN A
S
WITCH STATEMENT BE USED AROUND A
S
TRING
............................................................. 51
G
UESS THE OUTPUT OF THIS FOR LOOP
.................................................................................... 51
W
HAT IS AN
E
NHANCED
F
OR
L
OOP
? ....................................................................................... 51
W
HAT IS THE OUTPUT OF THE FOR LOOP BELOW
? ...................................................................... 51
W
HAT IS THE OUTPUT OF THE PROGRAM BELOW
? ..................................................................... 51
W
HAT IS THE OUTPUT OF THE PROGRAM BELOW
? ..................................................................... 52
W
HY IS
E
XCEPTION
H
ANDLING IMPORTANT
? ............................................................................ 53
W
HAT DESIGN PATTERN IS USED TO IMPLEMENT
E
XCEPTION HANDLING
F
EATURES IN MOST LANGUAGES
?
........................................................................................................................................ 53
.
W
HAT IS THE NEED FOR FINALLY BLOCK
? .................................................................................. 54
I
N WHAT SCENARIOS IS CODE IN FINALLY NOT EXECUTED
? ........................................................... 55
.
W
ILL FINALLY BE EXECUTED IN THE PROGRAM BELOW
? ............................................................... 56
I
S TRY WITHOUT A CATCH IS ALLOWED
? ................................................................................... 56
I
S TRY WITHOUT CATCH AND FINALLY ALLOWED
? ....................................................................... 56
C
AN YOU EXPLAIN THE HIERARCHY OF
E
XCEPTION
H
ANDLING CLASSES
? ......................................... 57
W
HAT IS THE DIFFERENCE BETWEEN
E
RROR AND
E
XCEPTION
? ..................................................... 57
W
HAT IS THE DIFFERENCE BETWEEN
C
HECKED
E
XCEPTIONS AND
U
NCHECKED
E
XCEPTIONS
? ............. 57
H
OW DO YOU THROW AN EXCEPTION FROM A METHOD
? ............................................................ 58
W
HAT HAPPENS WHEN YOU THROW A
C
HECKED
E
XCEPTION FROM A METHOD
? ............................. 58
CONDITIONS & LOOPS ....................................................................................................................... 49
EXCEPTION HANDLING ....................................................................................................................... 53

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