Advance JAVA
Multiple
Choice Questions and Answers:-
1. Which of these class is used to make a thread?
a) String
b) System
c) Thread
d) Runnable
Answer : c
Explanation : Thread class is used to make threads in java,
Thread encapsulates a thread of execution.
To
create a new thread the program will either extend Thread or implement the
Runnable interface.
2. Which of these interface is implemented by Thread class?
a) Runnable
b) Connections
c) Set
d) MapConnections
Answer : a
Explanation : None.
3. Which of these method of Thread class is used to find out
the priority given to a thread?
a) get()
b) ThreadPriority()
c) getPriority()
d)
getThreadPriority()
Answer : c
Explanation : None.
5. Which of these method of Thread class is used to Suspend
a thread for a period of time?
a) sleep()
b) terminate()
c) suspend()
d) stop()
Answer : a
Explanation : None.
6. Which function of pre defined class Thread is used to
check weather current thread being checked is still running?
a) isAlive()
b) Join()
c) isRunning()
d) Alive()
Answer : a
Explanation : isAlive() function is defined in class Thread,
it is used for implementing multithreading and
to check whether the thread called upon
is still running or not.
7. What is the output of this program?
1. class
multithreaded_programing {
2. public
static void main(String args[]) {
3. Thread t
= Thread.currentThread();
4.
t.setName("New Thread");
5.
System.out.println(t);
6. }
7. }
a) Thread[5,main]
b) Thread[New
Thread,5]
c)
Thread[main,5,main]
d) Thread[New
Thread,5,main]
Answer : d
Explanation : None.
Output:
$ javac
multithreaded_programing.java
$ java multithreaded_programing
Thread[New
Thread,5,main]
8. What is the priority of the thread in output of this
program?
1. class
multithreaded_programing {
2. public
static void main(String args[]) {
3. Thread t
= Thread.currentThread();
4.
t.setName("New Thread");
5.
System.out.println(t.getName());
6. }
7. }
a) main
b) Thread
c) New Thread
d) Thread[New
Thread,5,main]
Answer : c
Explanation : The getName() function is used to obtain the
name of the thread, in this code the name given to thread is ‘New Thread’.
Output:
$ javac
multithreaded_programing.java
$ java
multithreaded_programing
New Thread
9. What is the name of the thread in output of this program?
1. class
multithreaded_programing {
2. public
static void main(String args[]) {
3. Thread t
= Thread.currentThread();
4.
System.out.println(t.getPriority());
5. }
6. }
a) 0
b) 1
c) 4
d) 5
Answer : d
Explanation : The default priority given to a thread is 5.
Output:
$ javac
multithreaded_programing.java
$ java
multithreaded_programing
5
10. What is the name of the thread in output of this
program?
1. class
multithreaded_programing {
2. public
static void main(String args[]) {
3. Thread t
= Thread.currentThread();
4.
System.out.println(t.isAlive());
5. }
6. }
a) 0
b) 1
c) true
d) false
Answer : c
Explanation : Thread
t is seeded to currently program, hence when you run the program the thread
becomes active & code ‘t.isAlive’ returns true.
Output:
$ javac
multithreaded_programing.java
$ java
multithreaded_programing
true
11. What is multithreaded programming?
a) It’s a process in
which two different processes run simultaneously.
b) It’s a process in
which two or more parts of same process run simultaneously.
c) Its a process in
which many different process are able to access same information.
d) Its a process in
which a single process can access information from many sources.
Answer : b
Explanation : multithreaded programming a process in which
two or more parts of same process run simultaneously.
12. Which of these are types of multitasking?
a) Process based
b) Thread based
c) Process and Thread
based
d) None of the
mentioned
Answer : c
Explanation : There are two types of multitasking: Process
based multitasking and Thread based multitasking.
13. Which of these packages contain all the Java’s built in
exceptions?
a) java.io
b) java.util
c) java.lang
d) java.net
Answer : c
Explanation : None.
14. Thread priority in Java is?
a) Integer
b) Float
c) double
d) long
Answer : a
Explanation : Java assigns to each thread a priority that
determines hoe that thread should be treated with respect to others.
Thread priority are integers that specify
relative priority of one thread to another.
15. What will happen if two thread of same priority are
called to be processed simultaneously?
a) Any one will be
executed first lexographically
b) Both of them will
be executed simultaneously
c) None of them will
be executed
d) It is dependent on
the operating system.
Answer : d
Explanation : In cases where two or more thread with same
priority are competing for CPU cycles,
different operating system handle this
situation differently. Some execute them in time sliced manner some depending
on the thread they call.
16. Which of these statements is incorrect?
a) By multithreading
CPU’s idle time is minimized, and we can take maximum use of it.
b) By multitasking
CPU’s idle time is minimized, and we can take maximum use of it.
c) Two thread in Java
can have same priority
d) A thread can exist
only in two states, running and blocked.
Answer : d
Explanation : Thread exist in several states, a thread can
be running, suspended, blocked, terminated & ready to run.
17. What is the output of this program?
1. class
multithreaded_programing {
2. public
static void main(String args[]) {
3. Thread t
= Thread.currentThread();
4.
System.out.println(t);
5. }
6. }
a) Thread[5,main]
b) Thread[main,5]
c) Thread[main,0]
d) Thread[main,5,main]
Answer : d
Explanation : None.
Output:
$ javac
multithreaded_programing.java
$ java
multithreaded_programing
Thread[main,5,main]
18. What is the priority of the thread in output of this
program?
1. class
multithreaded_programing {
2. public
static void main(String args[]) {
3. Thread t
= Thread.currentThread();
4.
System.out.println(t);
5. }
6. }
a) 4
b) 5
c) 0
d) 1
Answer : b
Explanation : The output of program is Thread[main,5,main],
in this priority assigned to the thread is 5. Its the default value.
Since we have not named the thread they
are named by the group to they belong i:e main method.
Output:
$ javac
multithreaded_programing.java
$ java
multithreaded_programing
Thread[main,5,main]
19. What is the name of the thread in output of this program?
1. class
multithreaded_programing {
2. public
static void main(String args[]) {
3. Thread t
= Thread.currentThread();
4.
System.out.println(t);
5. }
6. }
a) main
b) Thread
c) System
d) None of the
mentioned
Answer : a
Explanation : The output of program is Thread[main,5,main],
Since we have not explicitly named the thread they are named by the group
to they belong i:e main method. Hence
they are named ‘main’.
Output:
$ javac
multithreaded_programing.java
$ java
multithreaded_programing
Thread[main,5,main]
20. What is the name of the thread in output of this
program?
1. class
multithreaded_programing {
2. public
static void main(String args[]) {
3. Thread t = Thread.currentThread();
4.
System.out.println(t.isAlive());
5. }
6. }
a) 0
b) 1
c) true
d) false
Answer : a
Explanation : Thread
t is seeded to currently program, hence when you run the program the thread
becomes active & code ‘t.isAlive’ returns true.
Output:
$ javac
multithreaded_programing.java
$ java
multithreaded_programing
true
21. Which of these packages contain all the collection
classes?
a) java.lang
b) java.util
c) java.net
d) java.awt
Answer : b
Explanation : None.
22. Which of these classes is not part of Java’s collection
framework?
a) Maps
b) Array
c) Stack
d) Queue
Answer : d
Explanation : Queue is not a part of collection framework.
23. Which of these interface is not a part of Java’s
collection framework?
a) List
b) Set
c) SortedMap
d) SortedList
Answer : d
Explanation : SortedList is not a part of collection
framework.
24. Which of these methods deletes all the elements from
invoking collection?
a) clear()
b) reset()
c) delete()
d) refresh()
Answer : a
Explanation : clear() method removes all the elements from
invoking collection.
25. What is Collection in Java?
a) A group of objects
b) A group of classes
c) A group of
interfaces
d) None of the
mentioned
Answer : a
Explanation : A collection is a group of objects, it is
similar to String Template Library (STL) of C++ programming language.
26. What is the output of this program?
1. import
java.util.*;
2. class Array {
3. public
static void main(String args[]) {
4. int
array[] = new int [5];
5. for (int
i = 5; i > 0; i--)
6.
array[5-i] = i;
7.
Arrays.fill(array, 1, 4, 8);
8. for (int
i = 0; i < 5 ; i++)
9.
System.out.print(array[i]);
10. }
11. }
a) 12885
b) 12845
c) 58881
d) 54881
Answer : c
Explanation : array was containing 5,4,3,2,1 but when method
Arrays.fill(array, 1, 4, 8) is called it fills the index location
starting with 1 to 4 by value 8 hence
array becomes 5,8,8,8,1.
Output:
$ javac Array.java
$ java Array
58881
27. What is the output of this program?
1. import
java.util.*;
2. class vector {
3. public
static void main(String args[]) {
4. Vector
obj = new Vector(4,2);
5.
obj.addElement(new Integer(3));
6. obj.addElement(new
Integer(2));
7.
obj.addElement(new Integer(5));
8.
obj.removeAll(obj);
9.
System.out.println(obj.isEmpty());
10. }
11. }
a) 0
b) 1
c) true
d) false
Answer : c
Explanation : firstly elements 3, 2, 5 are entered in the
vector obj, but when obj.removeAll(obj); is executed all the elements are
deleted and
vector is empty, hence obj.isEmpty()
returns true.
Output:
$ javac vector.java
$ java vector
true
28. What is the output of this program?
1. import
java.util.*;
2. class stack {
3. public
static void main(String args[]) {
4. Stack
obj = new Stack();
5.
obj.push(new Integer(3));
6.
obj.push(new Integer(2));
7. obj.pop();
8.
obj.push(new Integer(5));
9. System.out.println(obj);
10. }
11. }
a) [3, 5]
b) [3, 2]
c) [3, 2, 5]
d) [3, 5, 2]
Answer : a
Explanation : push() and pop() are standard functions of the
class stack, push() inserts in the stack and pop removes from the stack.
3 & 2 are inserted using push() the
pop() is used which removes 2 from the stack then again push is used to insert
5 hence stack contains elements 3 & 5.
Output:
$ javac stack.java
$ java stack
[3, 5]
29. What is the output of this program?
1. import
java.util.*;
2. class hashtable
{
3. public
static void main(String args[]) {
4. Hashtable
obj = new Hashtable();
5.
obj.put("A", new Integer(3));
6.
obj.put("B", new Integer(2));
7.
obj.put("C", new Integer(8));
8.
obj.remove(new String("A"));
9.
System.out.print(obj);
10. }
11. }
a) {C=8, B=2}
b) [C=8, B=2]
c) {A=3, C=8, B=2}
d) [A=3, C=8, B=2]
Answer : b
Explanation : None.
Output:
$ javac
hashtable.java
$ java hashtable
{C=8, B=2}
30. What is the output of this program?
1. import
java.util.*;
2. class Bitset {
3. public
static void main(String args[]) {
4. BitSet
obj = new BitSet(5);
5. for (int
i = 0; i < 5; ++i)
6.
obj.set(i);
7.
obj.clear(2);
8.
System.out.print(obj);
9. }
10. }
a) {0, 1, 3, 4}
b) {0, 1, 2, 4}
c) {0, 1, 2, 3, 4}
d) {0, 0, 0, 3, 4}
Answer : a
Explanation : None.
Output:
$ javac Bitset.java
$ java Bitset
{0, 1, 3, 4}
31. Which of these keywords is used to define packages in
Java?
a) pkg
b) Pkg
c) package
d) Package
Answer : c
Explanation : None.
32. Which of these is a mechanism for naming and visibility
control of a class and its content?
a) Object
b) Packages
c) Interfaces
d) None of the
Mentioned.
Answer : b
Explanation : Packages are both naming and visibility
control mechanism. We can define a class inside a package which is not
accessible by code outside the package.
33. Which of this access specifies can be used for a class
so that its members can be accessed by a different class in the same package?
a) Public
b) Protected
c) No Modifier
d) All of the
mentioned
Answer : d
Explanation : Either we can use public, protected or we can
name the class without any specifier.
34. Which of these access specifiers can be used for a class
so that it’s members can be accessed by a different class in the different
package?
a) Public
b) Protected
c) Private
d) No Modifier
Answer : a
Explanation : None.
35. Which of the following is correct way of importing an
entire package ‘pkg’?
a) import pkg.
b) Import pkg.
c) import pkg.*
d) Import pkg.*
Answer : c
Explanation : Operator * is used to import the entire
package.
36. Which of the following is incorrect statement about packages?
a) Package defines a
namespace in which classes are stored.
b) A package can
contain other package within it.
c) Java uses file
system directories to store packages.
d) A package can be
renamed without renaming the directory in which the classes are stored.
Answer : d
Explanation : A package can be renamed only after renaming
the directory in which the classes are stored.
37. Which of the following package stores all the standard
java classes?
a) lang
b) java
c) util
d) java.packages
Answer : b
Explanation : None.
38. What is the output of this program?
1. package pkg;
2. class display {
3. int x;
4. void show()
{
5. if (x
> 1)
6.
System.out.print(x + " ");
7. }
8. }
9. class packages {
10. public
static void main(String args[]) {
11.
display[] arr=new display[3];
12. for(int
i=0;i<3;i++)
13. arr[i]=new
display();
14.
arr[0].x = 0;
15.
arr[1].x = 1;
16.
arr[2].x = 2;
17. for
(int i = 0; i < 3; ++i)
18.
arr[i].show();
19. }
20. }
Note : packages.class file is in directory pkg;
a) 0
b) 1
c) 2
d) 0 1 2
Answer : c
Explanation : None.
Output:
$ javac packages.java
$ java packages
2
39. What is the output of this program?
1. package pkg;
2. class output {
3. public
static void main(String args[])
4. {
5.
StringBuffer s1 = new StringBuffer("Hello");
6.
s1.setCharAt(1, x);
7.
System.out.println(s1);
8. }
9. }
a) xello
b) xxxxx
c) Hxllo
d) Hexlo
Answer : c
Explanation : None.
Output:
$ javac output.java
$ java output
Hxllo
40. What is the output of this program?
1. package pkg;
2. class output {
3. public
static void main(String args[])
4. {
5. StringBuffer
s1 = new StringBuffer("Hello World");
6.
s1.insert(6 , "Good ");
7.
System.out.println(s1);
8. }
9. }
Note : Output.class file is not in directory pkg.
a) HelloGoodWorld
b) HellGoodoWorld
c) Compilation error
d) Runtime error
Answer : d
Explanation : Since output.class file is not in the
directory pkg in which class output is defined, program will not be able to
run.
output:
$ javac output.java
$ java output
can not find file
output.class
41. Which of these keywords is used to define interfaces in
Java?
a) interface
b) Interface
c) intf
d) Intf
Answer : a
Explanation : None.
42. Which of these can be used to fully abstract a class
from its implementation?
a) Objects
b) Packages
c) Interfaces
d) None of the
Mentioned.
Answer : c
Explanation : None.
43. Which of these access specifiers can be used for an
interface?
a) Public
b) Protected
c) private
d) All of the
mentioned
Answer : a
Explanation : Access specifier of interface is either public
or no specifier. When no access specifier is used then default access specifier
is used due to which interface is available only to other members of the
package in which it is declared, when declared public it can be used by any
code.
44. Which of these keywords is used by a class to use an
interface defined previously?
a) import
b) Import
c) implements
d) Implements
Answer : c
Explanation : interface is inherited by a class using
implements.
45. Which of the following is correct way of implementing an
interface salary by class manager?
a) class manager
extends salary {}
b) class manager
implements salary {}
c) class manager
imports salary {}
d) None of the
mentioned.
Answer : b
Explanation : None.
46. Which of the following is incorrect statement about
packages?
a) Interfaces
specifies what class must do but not how it does.
b) Interfaces are
specified public if they are to be accessed by any code in the program.
c) All variables in
interface are implicitly final and static.
d) All variables are
static and methods are public if interface is defined pubic.
Answer : d
Explanation : All methods and variables are implicitly
public if interface is declared public.
47. Which of the following package stores all the standard
java classes?
a) lang
b) java
c) util
d) java.packages
Answer : b
Explanation: None.
48. What is the output of this program?
1. interface
calculate {
2. void cal(int
item);
3. }
4. class display
implements calculate {
5. int x;
6. public void
cal(int item) {
7. x = item
* item;
8. }
9. }
10. class
interfaces {
11. public
static void main(String args[]) {
12. display arr = new display;
13. arr.x =
0;
14.
14.
arr.cal(2);
15.
System.out.print(arr.x);
16. }
17. }
a) 0
b) 2
c) 4
d) None of the
mentioned
Answer : c
Explanation : None.
Output:
$ javac
interfaces.java
$ java interfaces
4
49. What is the output of this program?
1. interface
calculate {
2. void cal(int
item);
3. }
4. class displayA
implements calculate {
5. int x;
6. public void
cal(int item) {
7. x = item
* item;
8. }
9. }
10. class displayB
implements calculate {
11. int x;
12. public void
cal(int item) {
13. x =
item / item;
14. }
15. }
16. class
interfaces {
17. public
static void main(String args[]) {
18.
displayA arr1 = new displayA;
19.
displayB arr2 = new displayB;
20. arr1.x
= 0;
21. arr2.x
= 0;
22. arr1.cal(2);
23.
arr2.cal(2);
24.
System.out.print(arr1.x + " " + arr2.x);
25. }
26. }
a) 0 0
b) 2 2
c) 4 1
d) 1 4
Answer : c
Explanation : class displayA implements the interface
calculate by doubling the value of item, where as class displayB implements the
interface by
dividing item by item, therefore variable
x of class displayA stores 4 and variable x of class displayB stores 1.
Output:
$ javac
interfaces.java
$ java interfaces
4 1
50. What is the output of this program?
1.interface calculate {
2. int VAR
= 0;
3. void
cal(int item);
4. }
5. class
display implements calculate {
6. int x;
7.
public void cal(int item) {
8. if (item<2)
9.
x = VAR;
10.
else
11.
x = item * item;
12. }
13. }
14. class interfaces {
15.
16. public
static void main(String args[]) {
17. display[] arr=new display[3];
18.
19.
for(int i=0;i<3;i++)
20.
arr[i]=new display();
21.
arr[0].cal(0);
22.
arr[1].cal(1);
23.
arr[2].cal(2);
24.
System.out.print(arr[0].x+" " + arr[1].x + " " +
arr[2].x);
25. }
26. }
a) 0 1 2
b) 0 2 4
c) 0 0 4
d) 0 1 4
Answer : c
Explanation : None.
output:
$ javac
interfaces.java
$ java interfaces
0 0 4
51. Which of these classes is not included in java.lang?
a) Byte
b) Integer
c) Array
d) Class
Answer : c
Explanation : Array class is a member of java.util.
52. Which of these is a process of converting a simple data
type into a class?
a) type wrapping
b) type conversion
c) type casting
d) None of the
Mentioned.
Answer : a
Explanation : None.
53. Which of these is a super class of wrappers Double &
Integer?
a) Long
b) Digits
c) Float
d) Number
Answer : d
Explanation : Number is an abstract class containing
subclasses Double, Float, Byte, Short, Integer and Long.
54. Which of these is wrapper for simple data type float?
a) float
b) double
c) Float
d) Double
Answer : c
Explanation : None.
55. Which of the following is method of wrapper Float for
converting the value of an object into byte?
a) bytevalue()
b) byte bytevalue()
c) Bytevalue()
d) Byte Bytevalue().
Answer : b
Explanation : None.
56. Which of these methods is used to check for infinitely
large and small values?
a) isInfinite()
b) isNaN()
c) Isinfinite()
d) IsNaN()
Answer : a
Explanation : isinfinite() method returns true is the value
being tested is infinitely large or small in magnitude.
57. Which of the following package stores all the simple
data types in java?
a) lang
b) java
c) util
d) java.packages
Answer : a
Explanation : None.
58. What is the output of this program?
1. class
isinfinite_output {
2. public
static void main(String args[]) {
3. Double d
= new Double(1 / 0.);
4. boolean
x = d.isInfinite();
5.
System.out.print(x);
6. }
7. }
a) 0
b) 1
c) true
d) false
Answer : c
Explanation : isInfinite() method returns true is the value
being tested is infinitely large or small in magnitude.
1/0. is infinitely large in magnitude
hence true is stored in x.
Output:
$ javac
isinfinite_output.java
$ java
isinfinite_output
true
59. What is the output of this program?
1. class
isNaN_output {
2. public
static void main(String args[]) {
3. Double d
= new Double(1 / 0.);
4. boolean
x = d.isNaN();
5.
System.out.print(x);
6. }
7. }
a) 0
b) 1
c) true
d) false
Answer : d
Explanation : isisNaN() method returns true is the value
being tested is a number. 1/0. is infinitely large in magnitude,
which cant not be defined as a number
hence false is stored in x.
Output:
$ javac
isNaN_output.java
$ java isNaN_output
false
60. What is the output of this program?
1. class binary {
2. public
static void main(String args[]) {
3. int num
= 17;
4.
System.out.print(Integer.toBinaryString(num));
5. }
6. }
a) 1001
b) 10011
c) 11011
d) 10001
Answer : d
Explanation : None.
output:
$ javac binary.java
$ java binary
10001
61. Which of these is a wrapper for data type int?
a) Integer
b) Long
c) Byte
d) Double
Answer : a
Explanation : None.
62. Which of the following methods is a method of wrapper
Integer for obtaining hash code for the invoking object?
a) int hash()
b) int hashcode()
c) int hashCode()
d) Integer hashcode()
Answer : c
Explanation : None.
63. Which of these is a super class of wrappers Long,
Character & Integer?
a) Long
b) Digits
c) Float
d) Number
Answer : d
Explanation : Number is an abstract class containing
subclasses Double, Float, Byte, Short, Integer and Long.
64. Which of these is wrapper for simple data type char?
a) Float
b) Character
c) String
d) Integer
Answer : b
Explanation : None.
65. Which of the following is method of wrapper Integer for
converting the value of an object into byte?
a) bytevalue()
b) byte bytevalue()
c) Bytevalue()
d) Byte Bytevalue().
Answer : b
Explanation : None.
66. Which of these methods is used to obtain value of
invoking object as a long?
a) long value()
b) long longValue()
c) Long longvalue()
d) Long Longvalue()
Answer : b
Explanation : long longValue() is used to obtain value of
invoking object as a long.
67. What is the output of this program?
1. class Output {
2. public
static void main(String args[]) {
3. char a[]
= {'a', '5', 'A', ' '};
4.
System.out.print(Character.isDigit(a[0]) + " ");
5.
System.out.print(Character.isWhitespace(a[3]) + " ");
6.
System.out.print(Character.isUpperCase(a[2]));
7. }
8. }
a) true false true
b) false true true
c) true true false
d) false false false
Answer : b
Explanation: Character.isDigit(a[0]) checks for a[0],
whether it is a digit or not, since a[0] i:e ‘a’ is a character false is
returned. a[3] is a whitespace
hence Character.isWhitespace(a[3]) returns
a true. a[2] is an upper case letter i:e ‘A’ hence Character.isUpperCase(a[2])
returns true.
Output:
$ javac Output.java
$ java Output
false true true
68. What is the output of this program?
1. class Output {
2. public
static void main(String args[]) {
3. Integer
i = new Integer(257);
4. byte x =
i.byteValue();
5.
System.out.print(x);
6. }
7. }
a) 0
b) 1
c) 256
d) 257
Answer : b
Explanation : i.byteValue() method returns the value of
wrapper i as a byte value. i is 257, range of byte is 256 therefore i value
exceeds
byte
range by 1 hence 1 is returned and stored in x.
Output:
$ javac Output.java
$ java Output
1
69. What is the output of this program?
1. class Output {
2. public
static void main(String args[]) {
3. Integer
i = new Integer(257);
4. float x
= i.floatValue();
5.
System.out.print(x);
6. }
7. }
a) 0
b) 1
c) 257
d) 257.0
Answer : d
Explanation : None.
Output:
$ javac Output.java
$ java Output
257.0
70. What is the output of this program?
1. class Output {
2. public
static void main(String args[]) {
3. Long i =
new Long(256);
4.
System.out.print(i.hashCode());
5. }
6. }
a) 256
b) 256.0
c) 256.00
d) 257.00
Answer : a
Explanation: None.
Output:
$ javac Output.java
$ java Output
256
71. Which of these class have only one field ‘TYPE’?
a) Void
b) Process
c) System
d) Runtime
Answer : a
Explanation : The Void class has one field, TYPE, which
holds a reference to the Class object for the type void.
72. Which of the following method of Process class can
terminate a process?
a) void kill()
b) void destroy()
c) void terminate()
d) void exit()
Answer : b
Explanation : Kills the subprocess. The subprocess
represented by this Process object is forcibly terminated.
73. Standard output variable ‘out’ is defined in which
class?
a) Void
b) Process
c) Runtime
d) System
Answer : d
Explanation : Standard output variable ‘out’ is defined in
System class. out is usually used in print statement i:e System.out.print().
74. Which of these class can encapsulate an entire executing
program?
a) Void
b) Process
c) Runtime
d) System
Answer : b
Explanation : None.
75. Which of the following is method of System class is used
to find how long a program takes to execute?
a) currenttime()
b) currentTime()
c)
currentTimeMillis()
d)
currenttimeMillis()
Answer : c
Explanation : None.
76. Which of these class holds a collection of static
methods and variables?
a) Void
b) Process
c) Runtime
d) System
Answer : d
Explanation : System class holds a collection of static
methods and variables. The standard input, output and error output of
java run time are stored in the in, out
and err variables of System class.
77. What is the output of this program?
1. class Output {
2. public
static void main(String args[]) {
3. long
start, end;
4. start =
System.currentTimeMillis();
5. for (int
i = 0; i < 10000000; i++);
6. end =
System.currentTimeMillis();
7. System.out.print(end - start);
8. }
9. }
a) 0
b) 1
c) 1000
d) System Dependent
Answer : d
Explanation : end time is the time taken by loop to execute
it can be any non zero value depending on the System.
Output:
$ javac Output.java
$ java Output
78
78. What is the output of this program?
1. class Output {
2. public
static void main(String args[]) {
3. byte a[]
= { 65, 66, 67, 68, 69, 70 };
4. byte b[]
= { 71, 72, 73, 74, 75, 76 };
5. System.arraycopy(a , 0, b, 0,
a.length);
6.
System.out.print(new String(a) + " " + new String(b));
7. }
8. }
a) ABCDEF ABCDEF
b) ABCDEF GHIJKL
c) GHIJKL ABCDEF
d) GHIJKL GHIJKL
Answer : a
Explanation :
System.arraycopy() is a method of class System which is used to copy a string
into another string.
Output:
$ javac Output.java
$ java Output
ABCDEF ABCDEF
79. What is the output of this program?
1. class Output {
2. public
static void main(String args[]) {
3. byte a[]
= { 65, 66, 67, 68, 69, 70 };
4. byte b[]
= { 71, 72, 73, 74, 75, 76 };
5.
System.arraycopy(a, 2, b, 1, a.length-2);
6.
System.out.print(new String(a) + " " + new String(b));
7. }
8. }
a) ABCDEF GHIJKL
b) ABCDEF GCDEFL
c) GHIJKL ABCDEF
d) GCDEFL GHIJKL
Answer : b
Explanation : None.
Output:
$ javac Output.java
$ java Output
ABCDEF GCDEFL
80. What is the output of this program?
1. class Output {
2. public
static void main(String args[]) {
3. byte a[]
= { 65, 66, 67, 68, 69, 70 };
4. byte b[]
= { 71, 72, 73, 74, 75, 76 };
5.
System.arraycopy(a, 1, b, 3, 0);
6.
System.out.print(new String(a) + " " + new String(b));
7. }
8. }
a) ABCDEF GHIJKL
b) ABCDEF GCDEFL
c) GHIJKL ABCDEF
d) GCDEFL GHIJKL
Answer : a
Explanation : Since last parameter of
System.arraycopy(a,1,b,3,0) is 0 nothing is copied from array a to array b,
hence b remains as it is.
Output:
$ javac Output.java
$ java Output
ABCDEF GHIJKL
81. Which of these packages contain classes and interfaces
used for input & output operations of a program?
a) java.util
b) java.lang
c) java.io
d) All of the
mentioned
Answer: c
Explanation: java.io
provides support for input and output operations.
82. Which of these class is not a member class of java.io
package?
a) String
b) StringReader
c) Writer
d) File
Answer: a
Explanation: None.
83. Which of these interface is not a member of java.io
package?
a) DataInput
b) ObjectInput
c) ObjectFilter
d) FileFilter
Answer: c
Explanation: None.
84. Which of these class is not related to input and output
stream in terms of functioning?
a) File
b) Writer
c) InputStream
d) Reader
Answer: a
Explanation: A File
describes properties of a file, a File object is used to obtain or manipulate
the information associated with a disk file, such as the permissions, time
date, and directories path, and to navigate subdirectories.
85. Which of these is specified by a File object?
a) a file in disk
b) directory path
c) directory in disk
d) None of the
mentioned
Answer: c
Explanation: None.
86. Which of these is method for testing whether the
specified element is a file or a directory?
a) IsFile()
b) isFile()
c) Isfile()
d) isfile()
Answer: b
Explanation: isFile()
returns true if called on a file and returns false when called on a directory.
87. What is the output of this program?
1. import
java.io.*;
2. class files {
3. public
static void main(String args[]) {
4. File obj
= new File("/java/system");
5.
System.out.print(obj.getName());
6. }
7. }
a) java
b) system
c) java/system
d) /java/system
Answer: b
Explanation:
obj.getName() returns the name of the file.
Output:
$ javac files.java
$ java files
system
88. What is the output of this program?
1. import
java.io.*;
2. class files {
3. public
static void main(String args[]) {
4. File obj
= new File("/java/system");
5.
System.out.print(obj.getAbsolutePath());
6. }
7. }
Note: file is made in c drive.
a) java
b) system
c) java/system
d) /java/system
Answer: d
Explanation: None.
Output:
$ javac files.java
$ java files
\java\system
89. What is the output of this program?
1. import
java.io.*;
2. class files {
3. public
static void main(String args[]) {
4. File obj
= new File("/java/system");
5.
System.out.print(obj.canWrite());
6.
System.out.print(" " + obj.canRead());
7. }
8. }
Note: file is made in c drive.
a) true false
b) false true
c) true true
d) false false
Answer: d
Explanation: None.
Output:
$ javac files.java
$ java files
false false
90. What is the output of this program?
1. import
java.io.*;
2. class files {
3. public
static void main(String args[]) {
4. File obj
= new File("/java/system");
5.
System.out.print(obj.getParent());
6.
System.out.print(" " + obj.isFile());
7. }
8. }
Note: file is made in c drive.
a) java true
b) java false
c) \java false
d) \java true
Answer: c
Explanation:
getparent() giver the parent directory of the file and isfile() checks weather
the present file is a directory or a file in the disk
Output:
$ javac files.java
$ java files
\java false
91. Which of these classes is used for input and output
operation when working with bytes?
a) InputStream
b) Reader
c) Writer
d) All of the
mentioned
Answer: a
Explanation:
InputStream & OutputStream are designed for byte stream. Reader and writer
are designed for character stream.
92. Which of these class is used to read and write bytes in
a file?
a) FileReader
b) FileWriter
c) FileInputStream
d) InputStreamReader
Answer: c
Explanation: None.
93. Which of these method of InputStream is used to read
integer representation of next available byte input?
a) read()
b) scanf()
c) get()
d) getInteger()
Answer: a
Explanation: None.
94. Which of these data type is returned by every method of
OutputStream?
a) int
b) float
c) byte
d) None of the
mentioned
Answer: d
Explanation: Every
method of OutputStream returns void and throws an IOExeption in case of errors.
95. Which of these is a method to clear all the data present
in output buffers?
a) clear()
b) flush()
c) fflush()
d) close()
Answer: b
Explanation: None.
96. Which of these is method is used for writing bytes to an
outputstream?
a) put()
b) print()
c) printf()
d) write()
Answer: b
Explanation: write()
and read() are the two main methods of OutputStream & InputStream
respectively that are used for printing and reading the byte data.
97. What is the output of this program?
1. import
java.io.*;
2. class
filesinputoutput {
3. public
static void main(String args[]) {
4.
InputStream obj = new FileInputStream("inputoutput.java");
5.
System.out.print(obj.available());
6. }
7. }
Note: inputoutput.java is stored in the disk.
a) true
b) false
c) prints number of
bytes in file
d) prints number of
characters in the file
Answer: c
Explanation:
obj.available() returns the number of bytes.
Output:
$ javac
filesinputoutput.java
$ java
filesinputoutput
1422
(Output will be
different in your case)
98. What is the output of this program?
1. import
java.io.*;
2. public class
filesinputoutput {
3. public static void main(String[] args) {
4. String obj
= "abc";
5. byte b[]
= obj.getBytes();
6.
ByteArrayInputStream obj1 = new ByteArrayInputStream(b);
7. for (int
i = 0; i < 2; ++ i) {
8. int
c;
9. while
((c = obj1.read()) != -1) {
10. if(i == 0) {
11. System.out.print((char)c);
12. }
13. }
14. }
15. }
16. }
a) abc
b) ABC
c) ab
d) AB
Answer: a
Explanation: None.
Output:
$ javac
filesinputoutput.java
$ java
filesinputoutput
abc
99. What is the output of this program?
1. import
java.io.*;
2. public class
filesinputoutput {
3. public static void main(String[] args) {
4. String obj
= "abc";
5. byte b[]
= obj.getBytes();
6. ByteArrayInputStream
obj1 = new ByteArrayInputStream(b);
7. for (int
i = 0; i < 2; ++ i) {
8. int
c;
9. while
((c = obj1.read()) != -1) {
10. if (i == 0) {
11.
System.out.print(Character.toUpperCase((char)c));
12. }
13. }
14. }
15. }
16. }
a) abc
b) ABC
c) ab
d) AB
Answer: b
Explanation: None.
Output:
$ javac
filesinputoutput.java
$ java
filesinputoutput
ABC
100. What is the output of this program?
1. import
java.io.*;
2. public class
filesinputoutput {
3. public static void main(String[] args) {
4. String obj
= "abc";
5. byte b[]
= obj.getBytes();
6. ByteArrayInputStream
obj1 = new ByteArrayInputStream(b);
7. for (int
i = 0; i < 2; ++ i) {
8. int
c;
9. while
((c = obj1.read()) != -1) {
10. if (i == 0) {
11.
System.out.print(Character.toUpperCase((char)c));
12.
obj2.write(1);
13. }
14. }
15.
System.out.print(obj2);
16. }
17. }
18. }
a) AaBaCa
b) ABCaaa
c) AaaBaaCaa
d) AaBaaCaaa
Answer: d
Explanation: None.
Output:
$ javac
filesinputoutput.java
$ java
filesinputoutput
AaBaaCaaa
101. Which of these is a process of writing the state of an
object to a byte stream?
a) Serialization
b) Externalization
c) File Filtering
d) All of the
mentioned
Answer: a
Explanation:
Serialization is the process of writing the state of an object to a byte
stream. This is used when you want to save the state of your program to
persistent storage area.
102. Which of these process occur automatically by java run
time system?
a) Serialization
b) Garbage collection
c) File Filtering
d) All of the
mentioned
Answer: a
Explanation:
Serialization and deserialization occur automatically by java run time system,
Garbage collection also occur automatically but is done by CPU or the operating
system not by the java run time system.
103. Which of these is an interface for control over
serialization and deserialization?
a) Serializable
b) Externalization
c) FileFilter
d) ObjectInput
Answer: b
Explanation: None.
104. Which of these interface extends DataOutput interface?
a) Serializable
b) Externalization
c) ObjectOutput
d) ObjectInput
Answer: c
Explanation:
ObjectOutput interface extends the DataOutput interface and supports object
serialization.
105. Which of these is a method of ObjectOutput interface
used to finalize the output state so that any buffers are cleared?
a) clear()
b) flush()
c) fflush()
d) close()
Answer: b
Explanation: None.
106. Which of these is method of ObjectOutput interface used
to write the object to input or output stream as required?
a) write()
b) Write()
c) StreamWrite()
d) writeObject()
Answer: d
Explanation:
writeObject() is used to write an object into invoking stream, it can be input
stream or output stream.
107. What is the output of this program?
1. import
java.io.*;
2. class
serialization {
3. public
static void main(String[] args) {
4. try {
5.
Myclass object1 = new Myclass("Hello", -7, 2.1e10);
6. FileOutputStream fos = new
FileOutputStream("serial");
7. ObjectOutputStream oos = new
ObjectOutputStream(fos);
8.
oos.writeObject(object1);
9.
oos.flush();
10.
oos.close();
11. }
12. catch(Exception e) {
13.
System.out.println("Serialization" + e);
14.
System.exit(0);
15. }
16. try {
17.
Myclass object2;
18. FileInputStream fis = new
FileInputStream("serial");
19. ObjectInputStream ois = new
ObjectInputStream(fis);
20. object2 = (Myclass)ois.readObject();
21.
ois.close();
22. System.out.println(object2);
23. }
24. catch (Exception e) {
25.
System.out.print("deserialization" + e);
26. System.exit(0);
27. }
28. }
29. }
30. class Myclass
implements Serializable {
31. String s;
32. int i;
33. double d;
34. Myclass
(String s, int i, double d){
35. this.d = d;
36. this.i = i;
37. this.s = s;
38. }
39. }
a) s=Hello; i=-7;
d=2.1E10
b) Hello; -7; 2.1E10
c) s; i; 2.1E10
d) Serialization
Answer: a
Explanation: None.
Output:
$ javac
serialization.java
$ java serialization
s=Hello; i=-7;
d=2.1E10
108. What is the output of this program?
1. import java.io.*;
2. class
serialization {
3. public
static void main(String[] args) {
4. try {
5.
Myclass object1 = new Myclass("Hello", -7, 2.1e10);
6. FileOutputStream fos = new
FileOutputStream("serial");
7. ObjectOutputStream oos = new
ObjectOutputStream(fos);
8.
oos.writeObject(object1);
9.
oos.flush();
10.
oos.close();
11. }
12. catch(Exception e) {
13. System.out.println("Serialization"
+ e);
14.
System.exit(0);
15. }
16. try {
17. int x;
18. FileInputStream fis = new
FileInputStream("serial");
19. ObjectInputStream ois = new
ObjectInputStream(fis);
20. x =
ois.readInt();
21.
ois.close();
22. System.out.println(x);
23. }
24. catch (Exception e) {
25.
System.out.print("deserialization");
26. System.exit(0);
27. }
28. }
29. }
30. class Myclass
implements Serializable {
31. String s;
32. int i;
33. double d;
34.
Myclass(String s, int i, double d){
35. this.d = d;
36. this.i = i;
37. this.s = s;
38. }
39. }
a) -7
b) Hello
c) 2.1E10
d) deserialization
Answer: d
Explanation: x =
ois.readInt(); will try to read an integer value from the stream ‘serial’
created before, since stream contains an object of Myclass hence error will
occur and it will be catched by catch printing deserialization.
Output:
$ javac
serialization.java
$ java serialization
deserialization
109. What is the output of this program?
1. import
java.io.*;
2. class
Chararrayinput {
3. public
static void main(String[] args) {
4. String obj
= "abcdefgh";
5. int
length = obj.length();
6. char c[]
= new char[length];
7.
obj.getChars(0, length, c, 0);
8.
CharArrayReader input1 = new CharArrayReader(c);
9.
CharArrayReader input2 = new CharArrayReader(c, 1, 4);
10. int i;
11. int j;
12. try {
13. while
((i = input1.read()) == (j = input2.read())) {
14.
System.out.print((char)i);
15. }
16. }
17. catch (IOException e) {
18.
e.printStackTrace();
19. }
20. }
21. }
a) abc
b) abcd
c) abcde
d) None of the
mentioned
Answer: d
Explanation: No
output is printed. CharArrayReader object input1 contains string “abcdefgh” whereas
object input2 contains string “bcde”, when
while((i=input1.read())==(j=input2.read())) is executed the starting character
of each object is compared since they are unequal control comes out of loop and
nothing is printed on the screen.
Output:
$ javac
Chararrayinput.java
$ java Chararrayinput
110. What is the output of this program?
1. import
java.io.*;
2. class streams {
3. public
static void main(String[] args) {
4. try {
5. FileOutputStream fos = new FileOutputStream("serial");
6. ObjectOutputStream oos = new
ObjectOutputStream(fos);
7.
oos.writeFloat(3.5);
8.
oos.flush();
9.
oos.close();
10. }
11. catch(Exception e) {
12. System.out.println("Serialization"
+ e);
13.
System.exit(0);
14. }
15. try {
16. float x;
17. FileInputStream fis = new
FileInputStream("serial");
18. ObjectInputStream ois = new
ObjectInputStream(fis);
19. x =
ois.readInt();
20.
ois.close();
21. System.out.println(x);
22. }
23. catch (Exception e) {
24.
System.out.print("deserialization");
25. System.exit(0);
26. }
27. }
28. }
a) 3
b) 3.5
c) serialization
d) deserialization
Answer: b
Explanation:
oos.writeFloat(3.5); writes in output stream which is extracted by x =
ois.readInt(); and stored in x hence x contains 3.5.
Output:
$ javac streams.java
$ java streams
3.5
111. Which of these is a process of extracting/removing the
state of an object from a stream?
a) Serialization
b) Externalization
c) File Filtering
d) Deserialization
Answer: d
Explanation:
Deserialization is a process by which the data written in the stream can be
extracted out from the stream.
112. Which of these process occur automatically by java run
time system?
a) Serialization
b) Memory allocation
c) Deserialization
d) All of the
mentioned
Answer: d
Explanation:
Serialization, deserialization and Memory allocation occur automatically by
java run time system.
113. Which of these is an interface for control over
serialization and deserialization?
a) Serializable
b) Externalization
c) FileFilter
d) ObjectInput
Answer: b
Explanation: None.
114. Which of these interface extends DataInput interface?
a) Serializable
b) Externalization
c) ObjectOutput
d) ObjectInput
Answer: d
Explanation:
ObjectInput interface extends the DataInput interface and supports object
serialization.
115. Which of these is a method of ObjectInput interface
used to deserialize an object from a stream?
a) int read()
b) void close()
c) Object
readObject()
d) Object
WriteObject()
Answer: c
Explanation: None.
116. Which of these class extend InputStream class?
a) ObjectStream
b) ObjectInputStream
c) ObjectOutput
d) ObjectInput
Answer: b
Explanation:
ObjectInputStream class extends the InputStream class and implements the
ObjectInput interface.
117. What is the output of this program?
1. import
java.io.*;
2. class streams {
3. public
static void main(String[] args) {
4. try {
5. FileOutputStream fos = new
FileOutputStream("serial");
6. ObjectOutputStream oos = new
ObjectOutputStream(fos);
7. oos.writeInt(5);
8. oos.flush();
9. oos.close();
10. }
11. catch(Exception e) {
12.
System.out.println("Serialization" + e);
13.
System.exit(0);
14. }
15. try {
16. int z;
17. FileInputStream fis = new
FileInputStream("serial");
18. ObjectInputStream ois = new
ObjectInputStream(fis);
19. z = ois.readInt();
20. ois.close();
21. System.out.println(x);
22. }
23. catch (Exception e) {
24.
System.out.print("deserialization");
25. System.exit(0);
26. }
27. }
28. }
a) 5
b) void
c) serialization
d) deserialization
Answer: a
Explanation:
oos.writeInt(5); writes integer 5 in the Output stream which is extracted by z
= ois.readInt(); and stored in z hence z contains 5.
Output:
$ javac streams.java
$ java streams
5
118. What is the output of this program?
1. import
java.io.*;
2. class
serialization {
3. public
static void main(String[] args) {
4. try {
5. Myclass object1 = new
Myclass("Hello", -7, 2.1e10);
6. FileOutputStream fos = new
FileOutputStream("serial");
7. ObjectOutputStream oos = new
ObjectOutputStream(fos);
8. oos.writeObject(object1);
9. oos.flush();
10. oos.close();
11. }
12. catch(Exception e) {
13.
System.out.println("Serialization" + e);
14. System.exit(0);
15. }
16. try {
17. int x;
18. FileInputStream fis = new
FileInputStream("serial");
19. ObjectInputStream ois = new
ObjectInputStream(fis);
20. x = ois.readInt();
21. ois.close();
22. System.out.println(x);
23. }
24. catch (Exception e) {
25.
System.out.print("deserialization");
26. System.exit(0);
27. }
28. }
29. }
30. class Myclass
implements Serializable {
31. String s;
32. int i;
33. double d;
34. Myclass(String
s, int i, double d){
35. this.d = d;
36. this.i = i;
37. this.s = s;
38. }
39. }
a) -7
b) Hello
c) 2.1E10
d) deserialization
Answer: d
Explanation: x =
ois.readInt(); will try to read an integer value from the stream ‘serial’
created before, since stream contains an object of Myclass hence error will
occur and it will be catched by catch printing deserialization.
Output:
$ javac
serialization.java
$ java serialization
deserialization
119. What is the output of this program?
1. import
java.io.*;
2. class streams {
3. public
static void main(String[] args) {
4. try {
5. FileOutputStream fos = new
FileOutputStream("serial");
6. ObjectOutputStream oos = new
ObjectOutputStream(fos);
7. oos.writeFloat(3.5);
8. oos.flush();
9. oos.close();
10. }
11. catch(Exception e) {
12. System.out.println("Serialization"
+ e);
13.
System.exit(0);
14. }
15. try {
16. FileInputStream fis = new
FileInputStream("serial");
17. ObjectInputStream ois = new
ObjectInputStream(fis);
18. ois.close();
19. System.out.println(ois.available());
20. }
21. catch (Exception e) {
22.
System.out.print("deserialization");
23. System.exit(0);
24. }
25. }
26. }
a) 1
b) 2
c) 3
d) 4
Answer: d
Explanation: New
input stream is linked to streal ‘serials’, an object ‘ois’ of
ObjectInputStream is used to access this newly created stream, ois.close();
closes the stream hence we can’t access the stream and ois.available() returns
0.
Output:
$ javac streams.java
$ java streams
0
120. What is the output of this program?
1. import
java.io.*;
2. class streams {
3. public
static void main(String[] args) {
4. try {
5. FileOutputStream fos = new
FileOutputStream("serial");
6. ObjectOutputStream oos = new
ObjectOutputStream(fos);
7. oos.writeFloat(3.5);
8. oos.flush();
9. oos.close();
10. }
11. catch(Exception e) {
12. System.out.println("Serialization"
+ e);
13.
System.exit(0);
14. }
15. try {
16. FileInputStream fis = new
FileInputStream("serial");
17. ObjectInputStream ois = new
ObjectInputStream(fis);
18. System.out.println(ois.available());
19. }
20. catch (Exception e) {
21.
System.out.print("deserialization");
22. System.exit(0);
23. }
24. }
25. }
a) 1
b) 2
c) 3
d) 4
Answer: D
Explanation:
oos.writeFloat(3.5); writes 3.5 in output stream. A new input stream is linked
to stream ‘serials’, an object ‘ois’ of ObjectInputStream is used to access
this newly created stream, ois.available() gives the total number of byte in
the input stream since a float was written in the stream thus the stream
contains 4 byte, hence 4 is returned and printed.
Output:
$ javac streams.java
$ java streams
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