Core Java
Multiple Choice Question & Answer:-
1. What is the range of data type short in Java?
a) -128 to 127
b) -32768 to 32767
c) -2147483648 to 2147483647
d) None of the mentioned
Answer:b
Explanation:Short occupies 16 bits in memory. Its
range is from -32768 to 32767.
2. What is the range of data type byte in Java?
a) -128 to 127
b) -32768 to 32767
c) -2147483648 to 2147483647
d) None of the mentioned
Answer:a
Explanation:Byte occupies 8 bits in memory. Its range
is from -128 to 127.
3. Which of the following are legal lines of Java code?
1. int w = (int)888.8;
2. byte x = (byte)100L;
3. long y = (byte)100;
4. byte z = (byte)100L;
a) 1 and 2
b) 2 and 3
c) 3 and 4
d) All statements are correct.
Answer: d
Explanation:Statements (1), (2), (3), and (4) are
correct. (1) is correct because when a floating-point number (a double in this
case) is cast to an int, it simply loses the digits after the decimal.(2) and
(4) are correct because a long can be cast into a byte. If the long is over
127, it loses its most significant (leftmost) bits.(3) actually works, even
though a cast is not necessary, because a long can store a byte.
4. An expression involving byte, int, and literal numbers is
promoted to which of these?
a) int
b) long
c) byte
d) float
Answer: a
Explanation:An expression involving bytes, ints,
shorts, literal numbers, the entire expression is promoted to int before any
calculation is done.
5. Which of these literals can be contained in a data type
float variable?
a) 1.7e-308
b) 3.4e-038
c) 1.7e+308
d) 3.4e-050
Answer: b
Explanation:Range of data type float is 3.4e-038 to
3.4e+308.
6. Which data type value is returned by all transcendental
math functions?
a) int
b) float
c) double
d) long
Answer:c
7. Which of these keyword can be used in subclass to call
the constructor of superclass?
a) super
b) this
c) extent
d) extends
Answer: a
8. What is the process of defining a method in subclass
having same name & type signature as a method in its superclass?
a) Method overloading
b) Method overriding
c) Method hiding
d) None of the mentioned
Answer: b
9. Which of these keywords can be used to prevent Method
overriding?
a) static
b) constant
c) protected
d) final
Answer: d
Explanation: To disallow a method from being
overridden, specify final as a modifier at the start of its declaration.
Methods declared as final cannot be overridden.
10. Which of these is correct way of calling a constructor
having no parameters, of superclass A by subclass B?
a) super(void);
b) superclass.();
c) super.A();
d) super();
Answer: d
11. Which of the following statements are incorrect?
a) public members of class can be accessed by any code
in the program.
b) private members of class can only be accessed by
other members of the class.
c) private members of class can be inherited by a sub
class, and become protected members in sub class.
d) protected members of a class can be inherited by a
sub class, and become private members of the sub class.
Answer: c
Explanation: private members of a class cannot be
inherited by a sub class.
12. Which of these is supported by method overriding in
Java?
a) Abstraction
b) Encapsulation
c) Polymorphism
d) None of the mentioned
Answer: c
13. String in Java is a?
a) class
b) object
c) variable
d) character array
Answer: a
14. Which of these method of String class is used to obtain
character at specified index?
a) char()
b) Charat()
c) charat()
d) charAt()
Answer: d
15. Which of these keywords is used to refer to member of
base class from a sub class?
a) upper
b) super
c) this
d) None of the mentioned
Answer: b
Explanation: Whenever a subclass needs to refer to its
immediate superclass, it can do so by use of the keyword super.
16. Which of these method of String class can be used to
test to strings for equality?
a) isequal()
b) isequals()
c) equal()
d) equals()
Answer: d
17. Which of the following statements are incorrect?
a) String is a class.
b) Strings in java are mutable.
c) Every string is an object of class String.
d) Java defines a peer class of String, called
StringBuffer, which allows string to be altered.
Answer: b
Explanation: Strings in Java are immutable that is
they can not be modified.
18. What is process of defining two or more methods within
same class that have same name but different parameters declaration?
a) method overloading
b) method overriding
c) method hiding
d) None of the mentioned
Answer: a
Explanation: Two or more methods can have same name as
long as their parameters declaration is different, the methods are said to be
overloaded and process is called method overloading. Method overloading is a
way by which Java implements polymorphism.
19. Which of these can be overloaded?
a) Methods
b) Constructors
c) All of the mentioned
d) None of the mentioned
Answer: c
20. Which of these is correct about passing an argument by
call-by-value process?
a) Copy of argument is made into the formal parameter
of the subroutine.
b) Reference to original argument is passed to formal
parameter of the subroutine.
c) Copy of argument is made into the formal parameter
of the subroutine and changes made on parameters of subroutine have effect on
original argument.
d) Reference to original argument is passed to formal
parameter of the subroutine and changes made on parameters of subroutine have
effect on original argument.
Answer: a
Explanation: When we pass an argument by call-by-value
a copy of argument is made into the formal parameter of the subroutine and
changes made on parameters of subroutine have no effect on original argument,
they remain the same.
21. What is the process of defining a method in terms of
itself, that is a method that calls itself?
a) Polymorphism
b) Abstraction
c) Encapsulation
d) Recursion
Answer: d
22. Which of the following statements are incorrect?
a) Default constructor is called at the time of
declaration of the object if a constructor has not been defined.
b) Constructor can be parameterized.
c) finalize() method is called when a object goes out
of scope and is no longer needed.
d) finalize() method must be declared protected.
Answer: c
Explanation: finalize() method is called just prior to
garbage collection. It is not called when object goes out of scope.
23. What is the numerical range of a char in Java?
a) -128 to 127
b) 0 to 256
c) 0 to 32767
d) 0 to 65535
Answer:d
Explanation: Char occupies 16-bit in memory, so it
supports 2^16 i:e from 0 to 65535.
24. Which of these coding types is used for data type
characters in Java?
a) ASCII
b) ISO-LATIN-1
c) UNICODE
d) None of the mentioned
Answer:c
Explanation: Unicode defines fully international
character set that can represent all the characters found in all human
languages. Its range is from 0 to 65536.
25. Which of these values can a boolean variable contain?
a) True & False
b) 0 & 1
c) Any integer value
d) true
Answer:a
Explanation: Boolean variable can contain only one of
two possible values, true and false.
26. Which of these occupy first 0 to 127 in Unicode
character set used for characters in Java?
a) ASCII
b) ISO-LATIN-1
c) None of the mentioned
d) ASCII and ISO-LATIN1
Answer:d
Explanation: First 0 to 127 character set in Unicode
are same as those of ISO-LAIN-1 and ASCII.
27. Which one is a valid declaration of a boolean?
a) boolean b1 = 1;
b) boolean b2 = ‘false’;
c) boolean b3 = false;
d) boolean b4 = ‘true’
Answer:c
Explanation: Boolean can only be assigned true or
false literals.
28. Which of these is data type long literal?
a) 0x99fffL
b) ABCDEFG
c) 0x99fffa
d) 99671246
Answer:a
Explanation:Data type long literals are appended by an
upper or lowercase L. 0x99fffL is hexadecimal long literal.
29. Which of these can be returned by the operator & ?
a) Integer
b) Boolean
c) Character
d) Integer or Boolean
Answer:d
Explanation: We can use binary ampersand operator on
integers/chars (and it returns an integer) or on booleans (and it returns a
boolean).
30. Literals in java must be preceded by which of these?
a) L
b) l
c) D
d) L and I
Answer:d
Explanation:Data type long literals are appended by an
upper or lowercase L.
31. Literal can be of which of these data types?
a) integer
b) float
c) boolean
d) all of the mentioned
Answer:d
32. Which of these can not be used for a variable name in
Java?
a) identifier
b) keyword
c) identifier & keyword
d) None of the mentioned
Answer:b
Explanation:Keywords are specially reserved words
which can not be used for naming a user defined variable, example : class, int,
for etc.
33. Which of these is incorrect string literal?
a) “Hello World”
b) “Hello\nWorld”
c) “\”Hello World””
d) “Hello
world”
Answer:d
Explanation:all string literals must begin and end in
same line.
34. Which of these is necessary condition for automatic type
conversion in Java?
a) The destination type is smaller than source type.
b) The destination type is larger than source type.
c) The destination type can be larger or smaller than
source type.
d) None of the mentioned
Answer:b
35. What is the prototype of the default constructor of this
class?
public class prototype { }
a) prototype( )
b) prototype(void)
c) public prototype(void)
d) public prototype( )
Answer: d
35. What is the error in this code?
byte b = 50;
b = b * 50;
a) b can not contain value 100, limited by its range.
b) * operator has converted b * 50 into int, which can
not be converted to byte without casting.
c) b can not contain value 50.
d) No error in this code
Answer: b
Explanation:While evaluating an expression containing
int, bytes or shorts , the whole expression is converted to int then evaluated
and result is also of type int
36. If an expression contains double, int, float, long, then
whole expression will promoted into which of these data types?
a) long
b) int
c) double
d) float
Answer: c
Explanation:If any operand is double the result of
expression is double.
37. What is Truncation is Java?
a) Floating-point value assigned to an integer type.
b) Integer value assigned to floating type.
c) Floating-point value assigned to an Floating type.
d) Integer value assigned to floating type.
Answer: a
38. Which of these operators is used to allocate memory to
array variable in Java?
a) malloc
b) alloc
c) new
d) new malloc
Answer:c
Explanation:Operator new allocates block of memory
specified by the size of array, and gives the reference of memory allocated to
the array variable.
39. Which of these is an incorrect array declaration?
a) int arr[] = new int[5]
b) int [] arr = new int[5]
c) int arr[] arr = new int[5]
d) int arr[] = int [5] new
Answer:d
Explanation:Operator new must be succeeded by array
type and array size.
40. What will this code print?
int arr[] = new int [5];
System.out.print(arr);
a) 0
b) value stored in arr[0].
c) 00000
d) Garbage value
Answer:d
Explanation:arr is an array variable, it is pointing
to array if integers. Printing arr will print garbage value. It is not same as
printing arr[0].
41. Which of these is an incorrect Statement?
a) It is necessary to use new operator to initialize
an array.
b) Array can be initialized using comma separated
expressions surrounded by curly braces.
c) Array can be initialized when they are declared.
d) None of the mentioned
Answer: a
Explanation:Array can be initialized using both new
and comma separated expressions surrounded by curly braces example : int arr[5]
= new int[5]; and int arr[] = { 0, 1, 2, 3, 4};
42. Which of these is necessary to specify at time of array
initialization?
a) Row
b) Column
c) Both Row and Column
d) None of the mentioned
Answer:a
43. Which of these keyword must be used to inherit a class?
a) super
b) this
c) extent
d) extends
Answer: d
44. Which of these keywords is used to refer to member of
base class from a sub class?
a) upper
b) super
c) this
d) None of the mentioned
Answer: b
Explanation: whenever a subclass needs to refer to its
immediate superclass, it can do so by use of the keyword super.
45. A class member declared protected becomes member of
subclass of which type?
a) public member
b) private member
c) protected member
d) static member
Answer: b
Explanation: A class member declared protected becomes
private member of subclass.
46. Which of these is correct way of inheriting class A by
class B?
a) class B + class A {}
b) class B inherits class A {}
c) class B extends A {}
d) class B extends class A {}
Answer: c
47. Which of the following statements are incorrect?
a) public members of class can be accessed by any code
in the program.
b) private members of class can only be accessed by
other members of the class.
c) private members of class can be inherited by a sub
class, and become protected members in sub class.
d) protected members of a class can be inherited by a
sub class, and become private members of the sub class.
Answer: c
Explanation: private members of a class cannot be
inherited by a sub class.
48. Which of the following can be operands of arithmetic
operators?
a) Numeric
b) Boolean
c) Characters
d) Both Numeric & Characters
Answer:d
Explanation: The operand of arithmetic operators can
be any of numeric or character type, But not boolean.
49. Modulus operator, %, can be applied to which of these?
a) Integers
b) Floating – point numbers
c) Both Integers and floating – point numbers.
d) None of the mentioned
Answer:c
Explanation: Modulus operator can be applied to both
integers and floating point numbers. .
50. With x = 0, which of the following are legal lines of
Java code for changing the value of x to 1?
1. x++;
2. x = x + 1;
3. x += 1;
4. x =+ 1;
a) 1, 2 & 3
b) 1 & 4
c) 1, 2, 3 & 4
d) 3 & 2
Answer: d
Explanation: Operator ++ increases value of variable
by 1. x = x + 1 can also be written in shorthand form as x += 1. Also x =+ 1
will set the value of x to 1.
51. Decrement operator, –, decreases value of variable by
what number?
a) 1
b) 2
c) 3
d) 4
Answer: a
52. Which of these statements are incorrect?
a) Assignment operators are more efficiently
implemented by Java run-time system than their equivalent long forms.
b) Assignment operators run faster than their
equivalent long forms.
c) Assignment operators can be used only with numeric
and character data type.
d) None
Answer: d
53. Which of these is not a bitwise operator?
a) &
b) &=
c) |=
d) <=
Answer:d
Explanation: <= is a relational operator.
54. Which operator is used to invert all the digits in
binary representation of a number?
a) ~
b) <<<
c) >>>
d) ^
Answer:a
Explanation: Unary not operator, ~, inverts all of the
bits of its operand in binary representation.
55. On applying Left shift operator, <<, on an integer
bits are lost one they are shifted past which position bit?
a) 1
b) 32
c) 33
d) 31
Answer: d
Explanation: The left shift operator shifts all of the
bite in a value to the left specified number of times. For each shift left, the
high order bit is shifted out and lost, zero is brought in from right. When a
left shift is applied to an integer operand, bits are lost once they are
shifted past the bit position 31.
56. Which right shift operator preserves the sign of the
value?
a) <<
b) >>
c) <<=
d) >>=
Answer: b
57. Which of these statements are incorrect?
a) The left shift operator, <<, shifts all of
the bite in a value to the left specified number of times.
b) The right shift operator, >>, shifts all of
the bite in a value to the right specified number of times.
c) The left shift operator can be used as an
alternative to multiplying by 2.
d) The right shift operator automatically fills the
higher order bits with 0.
Answer: d
Explanation: The right shift operator automatically
fills the higher order bit with its previous contents each time a shift occurs.
This also preserves the sign of the value.
58. What is the output of relational operators?
a) Integer
b) Boolean
c) Characters
d) Double
Answer: b
59. Which of these is returned by greater than, <, and
equal to, ==, operator?
a) Integers
b) Floating - point numbers
c) Boolean
d) None of the mentioned
Answer:c
Explanation: All relational operators return a boolean value
i:e true and false.
60. Which of the following operators can operate on a
boolean variable?
1. &&
2. ==
3. ?:
4. +=
a) 3 & 2
b) 1 & 4
c) 1, 2 & 4
d) 1, 2 & 3
Answer: d
Explanation: Operator Short circuit AND, &&,
equal to, == , ternary if-then-else, ?:, are boolean logical operators. += is
an arithmetic operator it can operate only on numeric values.
61. Which of these operators can skip evaluating right hand
operand?
a) !
b) |
c) &
d) &&
Answer: d
Explanation: Operator short circuit and, &&, and
short circuit or, ||, skip evaluating right hand operand when output can be
determined by left operand alone.
62. Which of these statement is correct?
a) true and false are numeric values 1 and 0.
b) true and false are numeric values 0 and 1.
c) true is any non zero value and false is 0.
d) true and false are non numeric values.
Answer: d
Explanation: true and false are keywords, they are non
numeric values which do no relate to zero or non zero numbers. true and false
are boolean values.
63. Which of these have highest precedence?
a) ()
b) ++
c) *
d) >>
Answer: a
Explanation: Order of precedence is (highest to
lowest) a -> b -> c -> d.
64. What should be expression1 evaluate to in using ternary
operator as in this line?
expression1 ? expression2 : expression3
a) Integer
b) Floating – point numbers
c) Boolean
d) None of the mentioned
Answer:c
Explanation: The controlling condition of ternary
operator must evaluate to boolean.
65. What is the value stored in x in following lines of
code?
int x, y, z;
x = 0;
y = 1;
x = y = z = 8;
a) 0
b) 1
c) 9
d) 8
Answer: d
66. What is the order of precedence (highest to lowest) of
following operators?
1. &
2. ^
3. ?:
a) 1 -> 2 -> 3
b) 2 -> 1 -> 3
c) 3 -> 2 -> 1
d) 2 -> 3 -> 1
Answer: a
67. Which of these statements are incorrect?
a) Equal to operator has least precedence.
b) Brackets () have highest precedence.
c) Division operator, /, has higher precedence than
multiplication operator.
d) Addition operator, +, and subtraction operator have
equal precedence.
Answer: c
Explanation: Division operator, /, has equal
precedence as of multiplication operator. In expression involving
multiplication and division evaluation of expression will begin from right side
when no brackets are used.
68. Which of these selection statements test only for
equality?
a) if
b) switch
c) if & switch
d) None of the mentioned
Answer: b
Explanation: switch statements checks for equality
between the controlling variable and its constant cases.
69. Which of these are selection statements in Java?
a) if()
b) for()
c) continue
d) break
Answer:a
Explanation: continue and break are jump statements,
and for is an looping statement.
70. Which of the following loops will execute the body of
loop even when condition controlling the loop is initially false?
a) do-while
b) while
c) for
d) None of the mentioned
Answer: a
71. Which of these jump statements can skip processing remainder
of code in its body for a particular iteration?
a) break
b) return
c) exit
d) continue
Answer: d
72. Which of these statement is correct?
a) switch statement is more efficient than a set of
nested ifs.
b) two case constants in the same switch can have
identical values.
c) switch statement can only test for equality,
whereas if statement can evaluate any type of boolean expression.
d) it is possible to create a nested switch
statements.
Answer: b
Explanation: No two case constants in the same switch
can have identical values.
73. What is the stored in the object obj in following lines
of code?
box obj;
a) Memory address of allocated memory of object.
b) NULL
c) Any arbitrary pointer
d) Garbage
Answer: b
Explanation: Memory is allocated to an object using
new operator. box obj; just declares a reference to object, no memory is
allocated to it hence it points to NULL.
74. Which of these keywords is used to make a class?
a) class
b) struct
c) int
d) None of the mentioned
Answer:a
75. Which of the following is a valid declaration of an
object of class Box?
a) Box obj = new Box();
b) Box obj = new Box;
c) obj = new Box();
d) new Box obj;
Answer: a
76. Which of these operators is used to allocate memory for
an object?
a) malloc
b) alloc
c) new
d) give
Answer: c
Explanation: Operator new dynamically allocates memory
for an object and returns a reference to it. This reference is address in memory
of the object allocated by new.
77. Which of these statement is incorrect?
a) Every class must contain a main() method.
b) Applets do not require a main() method at all.
c) There can be only one main() method in a program.
d) main() method must be made public.
Answer: a
Explanation: Every class does not need to have a
main() method, there can be only one main() method which is made public.
78. What is the return type of Constructors?
a) int
b) float
c) void
d) None of the mentioned
Answer: d
Explanation: Constructors does not have any return
type, not even void.
79. Which keyword is used by method to refer to the object
that invoked it?
a) import
b) catch
c) abstract
d) this
Answer: d
Explanation: this keyword can be used inside any
method to refer to the current object. this is always a reference to the object
on which the method was invoked.
80. Which of the following is a method having same name as
that of its class?
a) finalize
b) delete
c) class
d) constructor
Answer: d
Explanation: A constructor is a method that
initializes an object immediately upon creation. It has the same name as that
of class in which it resides.
81. Which operator is used by Java run time implementations
to free the memory of an object when it is no longer needed?
a) delete
b) free
c) new
d) None of the mentioned
Answer: d
Explanation: Java handles deallocation of memory
automatically, we do not need to explicitly delete an element. Garbage
collection only occurs during execution of the program. When no references to
the object exist, that object is assumed to be no longer needed, and the memory
occupied by the object can be reclaimed.
82. Which function is used to perform some action when the
object is to be destroyed?
a) finalize()
b) delete()
c) main()
d) None of the mentioned
Answer: a
83. Which of the folowing stements are incorrect?
a) Default constructor is called at the time of
declaration of the object if a constructor has not been defined.
b) Constructor can be parameterized.
c) finalize() method is called when a object goes out
of scope and is no longer needed.
d) finalize() method must be declared protected.
Answer: c
Explanation: finalize() method is called just prior to
garbage collection. it is not called when object goes out of scope.
84. Which of these lines of code will give better
performance?
1. a | 4 + c >> b & 7;
2. (a | ((( 4 * c ) >> b ) & 7 ))
a) 1 will give better performance as it has no
parentheses.
b) 2 will give better performance as it has
parentheses.
c) Both 1 & 2 will give equal performance.
d) Dependent on the computer system.
Answer: c
Explanation: Parentheses do not degrade the
performance of the program. Adding parentheses to reduce ambiguity does not
negatively affect your system.
85. What is the output of this program?
1. class average {
2. public
static void main(String args[])
3. {
4. double
num[] = {5.5, 10.1, 11, 12.8, 56.9, 2.5};
5. double
result;
6. result
= 0;
7. for
(int i = 0; i < 6; ++i)
8. result
= result + num[i];
9. System.out.print(result/6);
10.
11. }
12. }
a) 16.34
b) 16.566666644
c) 16.46666666666667
d) 16.46666666666666
Answer:c
Explanation:None.
output:
$ javac average.java
$ java average
16.46666666666667
86. What is the output of this program?
1. class conversion {
2. public
static void main(String args[])
3. {
4. double
a = 295.04;
5. int b
= 300;
6. byte
c = (byte) a;
7. byte
d = (byte) b;
8. System.out.println(c
+ " " + d);
9. }
10. }
a) 38 43
b) 39 44
c) 295 300
d) 295.04 300
Answer:b
Explanation:Type casting a larger variable into a
smaller variable results in modulo of larger variable by range of smaller
variable. b contains 300 which is larger than byte’s range i:e -128 to 127
hence d contains 300 modulo 256 i:e 44.
output:
$ javac conversion.java
$ java conversion
39 44
87. What is the output of this program?
1. class increment {
2. public
static void main(String args[])
3. {
4. int
g = 3;
5. System.out.print(++g
* 8);
6. }
7. }
a) 25
b) 24
c) 32
d) 33
Answer:c
Explanation:Operator ++ has more preference than *,
thus g becomes 4 and when multiplied by 8 gives 32.
output:
$ javac increment.java
$ java increment
32
88. What is the output of this program?
1. class area {
2. public
static void main(String args[])
3. {
4. double
r, pi, a;
5. r
= 9.8;
6. pi
= 3.14;
7. a
= pi * r * r;
8. System.out.println(a);
9. }
10. }
a) 301.5656
b) 301
c) 301.56
d) 301.56560000
Answer:a
output:
$ javac area.java
$ java area
301.5656
89. What is the output of this program?
1. class array_output {
2. public
static void main(String args[])
3. {
4. char
array_variable [] = new char[10];
5. for
(int i = 0; i < 10; ++i) {
6. array_variable[i]
= 'i';
7. System.out.print(array_variable[i]
+ "" );
8. i++;
9. }
10. }
11. }
a) i i i i i
b) 0 1 2 3 4
c) i j k l m
d) None of the mentioned
Answer:a
output:
$ javac array_output.java
$ java array_output
i i i i i
90. What is the output of this program?
1. class mainclass {
2. public
static void main(String args[])
3. {
4. char
a = 'A';
5. a++;
6. System.out.print((int)a);
7. }
8. }
a) 66
b) 67
c) 65
d) 64
Answer:a
Explanation: ASCII value of ‘A’ is 65, on using ++
operator character value increments by one.
output:
$ javac mainclass.java
$ java mainclass
66
91. What is the output of this program?
1. class mainclass {
2. public
static void main(String args[])
3. {
4. boolean
var1 = true;
5. boolean
var2 = false;
6. if
(var1)
7. System.out.println(var1);
8. else
9. System.out.println(var2);
10. }
11. }
a) 0
b) 1
c) true
d) false
Answer:c
output:
$ javac mainclass.java
$ java mainclass
true
92. What is the output of this program?
1. class booloperators {
2. public
static void main(String args[])
3. {
4. boolean
var1 = true;
5. boolean
var2 = false;
6. System.out.println((var2
& var2));
7. }
8. }
a) 0
b) 1
c) true
d) false
Answer:d
Explanation: boolean ‘&’ operator always returns
true or false. var1 is defined true and var2 is defined false hence their
‘&’ operator result is false.
output:
$ javac booloperators.java
$ java booloperators
false
93. What is the output of this program?
1. class asciicodes {
2. public
static void main(String args[])
3. {
4. char
var1 = 'A';
5. char
var2 = 'a';
6. System.out.println((int)var1
+ " " + (int)var2);
7. }
8. }
a) 162
b) 65 97
c) 67 95
d) 66 98
Answer:b
Explanation:ASCII code for ‘A’ is 65 and for ‘a’ is
97.
output:
$ javac asciicodes.java
$ java asciicodes
65 97
94. What is the output of this program?
1. class evaluate {
2. public
static void main(String args[])
3. {
4. int
a[] = {1,2,3,4,5};
5. int
d[] = a;
6. int
sum = 0;
7. for
(int j = 0; j < 3; ++j)
8. sum
+= (a[j] * d[j + 1]) + (a[j + 1] * d[j]);
9. System.out.println(sum);
10. }
11. }
a) 38
b) 39
c) 40
d) 41
Answer:c
output:
$ javac evaluate.java
$ java evaluate
40
95. What is the output of this program?
1. class array_output {
2. public
static void main(String args[])
3. {
4. int
array_variable [] = new int[10];
5. for
(int i = 0; i < 10; ++i) {
6. array_variable[i]
= i/2;
7. array_variable[i]++;
8. System.out.print(array_variable[i]
+ " ");
9. i++;
10. }
11.
12. }
13. }
a) 0 2 4 6 8
b) 1 2 3 4 5
c) 0 1 2 3 4 5 6 7 8 9
d) 1 2 3 4 5 6 7 8 9 10
Answer:b
Explanation:When an array is declared using new
operator then all of its elements are initialized to 0 automatically. for loop
body is executed 5 times as whenever controls comes in the loop i value is
incremented twice, first by i++ in body of loop then by ++i in increment
condition of for loop.
output:
$ javac array_output.java
$ java array_output
1 2 3 4 5
96. What is the output of this program?
1. class variable_scope {
2. public
static void main(String args[])
3. {
4. int
x;
5. x
= 5;
6. {
7. int
y = 6;
8. System.out.print(x
+ " " + y);
9. }
10. System.out.println(x
+ " " + y);
11. }
12. }
a) 5 6 5 6
b) 5 6 5
c) Runtime error
d) Compilation error
Answer:d
Explanation:Second print statement doesn’t have access
to y , scope y was limited to the block defined after initialization of x.
output:
$ javac variable_scope.java
Exception in thread “main” java.lang.Error: Unresolved
compilation problem: y cannot be resolved to a variable
97. What is the output of this program?
1. class dynamic_initialization {
2. public
static void main(String args[])
3. {
4. double
a, b;
5. a
= 3.0;
6. b
= 4.0;
7. double
c = Math.sqrt(a * a + b * b);
8. System.out.println(c);
9. }
10. }
a) 5.0
b) 25.0
c) 7.0
d) Compilation Error
Answer:a
Explanation:Variable c has been dynamically
initialized to square root of a * a + b * b, during run time.
output:
$ javac dynamic_initialization.java
$ java dynamic_initialization
5.0
98. What is the output of this program?
1. class char_increment {
2. public
static void main(String args[])
3. {
4. char
c1 = 'D';
5. char
c2 = 84;
6. c2++;
7. c1++;
8. System.out.println(c1
+ " " + c2);
9. }
10. }
a) E U
b) U E
c) V E
d) U F
Answer:a
Explanation:Operator ++ increments the value of
character by 1. c1 and c2 are given values D and 84, when we use ++ operator
their values increments by 1, c1 and c2 becomes E and U respectively.
output:
$ javac char_increment.java
$ java char_increment
E U
99. What is the output of this program?
1. class conversion {
2. public
static void main(String args[])
3. {
4. double
a = 295.04;
5. int b
= 300;
6. byte
c = (byte) a;
7. byte
d = (byte) b;
8. System.out.println(c
+ " " + d);
9. }
10. }
a) 38 43
b) 39 44
c) 295 300
d) 295.04 300
Answer:b
Explanation:Type casting a larger variable into a
smaller variable results in modulo of larger variable by range of smaller
variable. b contains 300 which is larger than byte’s range i:e -128 to 127
hence d contains 300 modulo 256 i:e 44.
output:
$ javac conversion.java
$ java conversion
39 44
100. What is the output of this program?
1. class A {
2. final
public int calculate(int a, int b) { return 1; }
3. }
4. class B extends A {
5. public int
calculate(int a, int b) { return 2; }
6. }
7. public class output {
8. public
static void main(String args[])
9. {
10. B
object = new B();
11. System.out.print("b
is " + b.calculate(0, 1));
12. }
13. }
a) b is : 2
b) b is : 1
c) Compilation Error.
d) An exception is thrown at runtime.
Answer:c
Explanation:The code does not compile because the
method calculate() in class A is final and so cannot be overridden by method of
class b.
9. What is the output of this program?
1. class main_arguments {
2. public
static void main(String [] args)
3. {
4. String
[][] argument = new String[2][2];
5. int
x;
6. argument[0]
= args;
7. x
= argument[0].length;
8. for
(int y = 0; y < x; y++)
9. System.out.print("
" +
argument[0][y]);
10. }
11. }
a) 1 1
b) 1 0
c) 1 0 3
d) 1 2 3
Answer:d
Explanation:In argument[0] = args;, the reference
variable arg[0], which was referring to an array with two elements, is
reassigned to an array (args) with three elements.
Output:
$ javac main_arguments.java
$ java main_arguments
1 2 3
10. What is the output of this program?
1. class c {
2. public
void main( String[] args )
3. {
4. System.out.println(
"Hello" + args[0] );
5. }
6. }
a) Hello c
b) Hello
c) Hello world
d) Runtime Error.
Answer:d
Explanation:A runtime error will occur owning to the
main method of the code fragment not being declared static.
Output:
$ javac c.java
Exception in thread “main”
java.lang.NoSuchMethodError: main
6. What is the output of this program?
1. class array_output {
2. public
static void main(String args[])
3. {
4. int
array_variable [] = new int[10];
5. for
(int i = 0; i < 10; ++i) {
6. array_variable[i]
= i;
7. System.out.print(array_variable[i]
+ " ");
8. i++;
9. }
10. }
11. }
a) 0 2 4 6 8
b) 1 3 5 7 9
c) 0 1 2 3 4 5 6 7 8 9
d) 1 2 3 4 5 6 7 8 9 10
Answer:a
Explanation:When an array is declared using new
operator then all of its elements are initialized to 0 automatically. for loop
body is executed 5 times as whenever controls comes in the loop i value is
incremented twice, first by i++ in body of loop then by ++i in increment
condition of for loop.
output:
$ javac array_output.java
$ java array_output
0 2 4 6 8
7. What is the output of this program?
1. class multidimention_array {
2. public
static void main(String args[])
3. {
4. int
arr[][] = new int[3][];
5. arr[0]
= new int[1];
6. arr[1]
= new int[2];
7. arr[2]
= new
int[3];
8. int
sum = 0;
9. for
(int i = 0; i < 3; ++i)
10. for
(int j = 0; j < i + 1; ++j)
11. arr[i][j]
= j + 1;
12. for
(int i = 0; i < 3; ++i)
13. for
(int j = 0; j < i + 1; ++j)
14. sum
+ = arr[i][j];
15. System.out.print(sum);
16. }
17. }
a) 11
b) 10
c) 13
d) 14
Answer:b
Explanation:arr[][] is a 2D array, array has been
allotted memory in parts. 1st row contains 1 element, 2nd row contains 2
elements and 3rd row contains 3 elements. each element of array is given i + j
value in loop. sum contains addition of all the elements of the array.
output:
$ javac multidimention_array.java
$ java multidimention_array
10
8. What is the output of this program?
1. class evaluate {
2. public
static void main(String args[])
3. {
4. int
arr[] = new int[] {0 , 1, 2, 3, 4, 5, 6, 7, 8, 9};
5. int
n = 6;
6. n
= arr[arr[n] / 2];
7. System.out.println(arr[n]
/ 2);
8. }
9. }
a) 3
b) 0
c) 6
d) 1
Answer:d
Explanation:Array arr contains 10 elements. n contains
6 thus in next line n is given value 2 printing arr[2]/2 i:e 2/2 = 1.
output:
$ javac evaluate.java
$ java evaluate
1
9. What is the output of this program?
1. class array_output {
2. public
static void main(String args[])
3. {
4. char
array_variable [] = new char[10];
5. for
(int i = 0; i < 10; ++i) {
6. array_variable[i]
= 'i';
7. System.out.print(array_variable[i]
+ "");
8. }
9. }
10. }
a) 1 2 3 4 5 6 7 8 9 10
b) 0 1 2 3 4 5 6 7 8 9 10
c) i j k l m n o p q r
d) i i i i i i i i i i
Answer:d
Explanation:None.
output:
$ javac array_output.java
$ java array_output
i i i i i i i i i i
10. What is the output of this program?
1. class array_output {
2. public
static void main(String args[])
3. {
4. int
array_variable[][] = {{ 1, 2, 3}, { 4 , 5, 6}, { 7, 8, 9}};
5. int
sum = 0;
6. for
(int i = 0; i < 3; ++i)
7. for
(int j = 0; j < 3 ; ++j)
8. sum
= sum + array_variable[i][j];
9. System.out.print(sum
/ 5);
10. }
11. }
a) 8
b) 9
c) 10
d) 11
Answer:b
Explanation:None.
output:
$ javac array_output.java
$ java array_output
9
6. What is the output of this program?
1. class increment {
2. public
static void main(String args[])
3. {
4. double
var1 = 1 + 5;
5. double
var2 = var1 / 4;
6. int
var3 = 1 + 5;
7. int
var4 = var3 / 4;
8. System.out.print(var2
+ " " + var4);
9.
10. }
11. }
a) 1 1
b) 0 1
c) 1.5 1
d) 1.5 1.0
Answer:c
output:
$ javac increment.java
$ java increment
1.5 1
7. What is the output of this program?
1. class Modulus {
2. public
static void main(String args[])
3. {
4. double
a = 25.64;
5. int b
= 25;
6. a
= a % 10;
7. b
= b % 10;
8. System.out.println(a
+ " " + b);
9. }
10. }
a) 5.640000000000001 5
b) 5.640000000000001 5.0
c) 5 5
d) 5 5.640000000000001
Answer: a
Explanation: Modulus operator returns the remainder of
a division operation on the operand. a = a % 10 returns 25.64 % 10 i:e
5.640000000000001. Similarly b = b % 10 returns 5.
output:
$ javac Modulus.java
$ java Modulus
5.640000000000001 5
8. What is the output of this program?
1. class increment {
2. public
static void main(String args[])
3. {
4. int
g = 3;
5. System.out.print(++g
* 8);
6. }
7. }
a) 25
b) 24
c) 32
d) 33
Answer:c
Explanation: Operator ++ has more preference than *,
thus g becomes 4 and when multiplied by 8 gives 32.
output:
$ javac increment.java
$ java increment
32
9. What is the output of this program?
1. class Output {
2. public
static void main(String args[])
3. {
4. int
x , y;
5. x
= 10;
6. x++;
7. --x;
8. y
= x++;
9. System.out.println(x
+ " " + y);
10. }
11. }
a) 11 11
b) 10 10
c) 11 10
d) 10 11
Answer: c
Explanation: x is initialized to 10 then increased by
1 by ++ operator making it 11. x is again decreased by — operator making it 10,
next x is incremented by post increment and intialized to y, here the value of
x obtained before increment operator is executed, so value of y is 10 and value
of x is 11.
output:
$ javac Output.java
$ java Output
11 10
10. What is the output of this program?
1. class Output {
2. public
static void main(String args[])
3. {
4. int
a = 1;
5. int
b = 2;
6. int
c;
7. int
d;
8. c
= ++b;
9. d
= a++;
10. c++;
11. b++;
12. ++a;
13. System.out.println(a
+ " " + b + " " + c);
14. }
15. }
a) 3 2 4
b) 3 2 3
c) 2 3 4
d) 3 4 4
Answer: d
output:
$ javac Output.java
$ java Output
3 4 4
6. What is the output of this program?
1. class bitwise_operator {
2. public
static void main(String args[])
3. {
4. int
var1 = 42;
5. int
var2 = ~var1;
6. System.out.print(var1
+ " " +
var2);
7. }
8. }
a) 42 42
b) 43 43
c) 42 -43
d) 42 43
Answer:c
Explanation: Unary not operator, ~, inverts all of the
bits of its operand. 42 in binary is 00101010 in using ~ operator on var1 and
assigning it to var2 we get inverted value of 42 i:e 11010101 which is -43 in
decimal.
output:
$ javac bitwise_operator.java
$ java bitwise_operator
42 -43
7. What is the output of this program?
1. class bitwise_operator {
2. public
static void main(String args[])
3. {
4. int
a = 3;
5. int
b = 6;
6. int
c = a | b;
7. int
d = a &
b;
8. System.out.println(c
+ " " + d);
9. }
10. }
a) 7 2
b) 7 7
c) 7 5
d) 5 2
Answer: a
Explanation: And operator produces 1 bit if both
operand are 1. Or operator produces 1 bit if any bit of the two operands in 1.
output:
$ javac bitwise_operator.java
$ java bitwise_operator
7 2
8. What is the output of this program?
1. class leftshift_operator {
2. public
static void main(String args[])
3. {
4. byte
x = 64;
5. int
i;
6. byte
y;
7. i
= x << 2;
8. y
= (byte) (x << 2)
9. System.out.print(i
+ " " + y);
10. }
11. }
a) 0 64
b) 64 0
c) 0 256
d) 256 0
Answer:d
output:
$ javac leftshift_operator.java
$ java leftshift_operator
256 0
9. What is the output of this program?
1. class rightshift_operator {
2. public
static void main(String args[])
3. {
4. int
x;
5. x
= 10;
6. x
= x >> 1;
7. System.out.println(x);
8. }
9. }
a) 10
b) 5
c) 2
d) 20
Answer: b
Explanation: Right shift operator, >>, devides
the value by 2.
output:
$ javac rightshift_operator.java
$ java rightshift_operator
5
10. What is the output of this program?
1. class Output {
2. public
static void main(String args[])
3. {
4. int
a = 1;
5. int
b = 2;
6. int
c = 3;
7. a
|= 4;
8. b
>>= 1;
9. c
<<= 1;
10. a
^= c;
11. System.out.println(a
+ " " + b + " " + c);
12. }
13. }
a) 3 1 6
b) 2 2 3
c) 2 3 4
d) 3 3 6
Answer: a
output:
$ javac Output.java
$ java Output
3 1 6
6. What is the output of this program?
1. class Relational_operator {
2. public
static void main(String args[])
3. {
4. int
var1 = 5;
5. int
var2 = 6;
6. System.out.print(var1
> var2);
7. }
8. }
a) 1
b) 0
c) true
d) false
Answer:d
Explanation: Operator > returns a boolean value. 5
is not greater than 6 therefore false is returned.
output:
$ javac Relational_operator.java
$ java Relational_operator
false
7. What is the output of this program?
1. class bool_operator {
2. public
static void main(String args[])
3. {
4. boolean
a = true;
5. boolean
b = !true;
6. boolean
c = a | b;
7. boolean
d = a & b;
8. boolean
e = d ? b : c;
9. System.out.println(d
+ " " + e);
10. }
11. }
a) false false
b) true ture
c) true false
d) false true
Answer: d
Explanation: Operator | returns true if any one
operand is true, thus ‘c = true | false’ is true. Operator & returns a true
if both of the operand is true thus d is false. Ternary operator ?: assigns
left of ‘:’ if condition is true and right hand of ‘:’ if condition is false. d
is false thus e = d ? b : c , assigns c to e , e contains true.
output:
$ javac bool_operator.java
$ java bool_operator
false true
8. What is the output of this program?
1. class ternary_operator {
2. public static
void main(String args[])
3. {
4. int
x = 3;
5. int
y = ~ x;
6. int
z;
7. z
= x > y ? x : y;
8. System.out.print(z);
9. }
10. }
a) 0
b) 1
c) 3
d) -4
Answer:c
output:
$ javac ternary_operator.java
$ java ternary_operator
3
9. What is the output of this program?
1. class Output {
2. public
static void main(String args[])
3. {
4. int
x , y = 1;
5. x
= 10;
6. if
(x != 10 && x / 0 == 0)
7. System.out.println(y);
8. else
9. System.out.println(++y);
10. }
11. }
a) 1
b) 2
c) Runtime error owing to division by zero in if
condition.
d) Unpredictable behavior of program.
Answer: b
Explanation: Operator short circuit and, &&,
skips evaluating right hand operand if left hand operand is false thus division
by zero in if condition does not give an error.
output:
$ javac Output.java
$ java Output
2
10. What is the output of this program?
1. class Output {
2. public
static void main(String args[])
3. {
4. boolean
a = true;
5. boolean
b = false;
6. boolean
c = a ^ b;
7. System.out.println(!c);
8. }
9. }
a) 0
b) 1
c) false
d) true
Answer: c
output:
$ javac Output.java
$ java Output
false
6. What is the output of this program?
1. class operators {
2. public
static void main(String args[])
3. {
4. int
var1 = 5;
5. int
var2 = 6;
6. int
var3;
7. var3
= ++ var2 * var1 / var2 + var2;
8. System.out.print(var3);
9. }
10. }
a) 10
b) 11
c) 12
d) 56
Answer:c
Explanation: Operator ++ has the highest precedence
than / , * and +. var2 is incremented to 7 and then used in expression, var3 =
7 * 5 / 7 + 7, gives 12.
output:
$ javac operators.java
$ java operators
12
7. What is the output of this program?
1. class operators {
2. public
static void main(String args[])
3. {
4. int
x = 8;
5. System.out.println(++x
* 3 + " " + x);
6. }
7. }
a) 24 8
b) 24 9
c) 27 8
d) 27 9
Answer: d
Explanation: Operator ++ has higher precedence than
multiplication operator, *, x is incremented to 9 than multiplied with 3 giving
27.
output:
$ javac operators.java
$ java operators
27 9
8. What is the output of this program?
1. class ternary_operator {
2. public
static void main(String args[])
3. {
4. int
x = 3;
5. int
y = ~ x;
6. int
z;
7. z
= x > y ? x : y;
8. System.out.print(z);
9. }
10. }
a) 0
b) 1
c) 3
d) -4
Answer:c
output:
$ javac ternary_operator.java
$ java ternary_operator
3
10. What is the output of this program?
1. class Output {
2. public
static void main(String args[])
3. {
4. int
x , y = 1;
5. x
= 10;
6. if
(x != 10 && x / 0 == 0)
7. System.out.println(y);
8. else
9. System.out.println(++y);
10. }
11. }
a) 1
b) 2
c) Runtime error owing to division by zero in if
condition.
d) Unpredictable behavior of program.
Answer: b
Explanation: Operator short circuit and, &&,
skips evaluating right hand operand if left hand operand is false thus division
by zero in if condition does not give an error.
output:
$ javac Output.java
$ java Output
2
6. What is the output of this program?
1. class selection_statements {
2. public
static void main(String args[])
3. {
4. int
var1 = 5;
5. int
var2 = 6;
6. if
((var2 = 1) == var1)
7. System.out.print(var2);
8. else
9. System.out.print(++var2);
10. }
11. }
a) 1
b) 2
c) 3
d) 4
Answer:b
Explanation: var2 is initialised to 1. The conditional
statement returns false and the else part gets executed.
output:
$ javac selection_statements.java
$ java selection_statements
2
7. What is the output of this program?
1. class comma_operator {
2. public
static void main(String args[])
3. {
4. int
sum = 0;
5. for
(int i = 0, j = 0; i < 5 & j < 5; ++i, j = i + 1)
6. sum
+= i;
7. System.out.println(sum);
8. }
9. }
a) 5
b) 6
c) 14
d) compilation error
Answer: b
Explanation: Using comma operator , we can include
more than one statement in the initialization and iteration portion of the for
loop. Therefore both ++i and j = i + 1 is executed i gets the value – 0,1,2,3,4
& j gets the values -0,1,2,3,4,5.
output:
$ javac comma_operator.java
$ java comma_operator
6
8. What is the output of this program?
1. class jump_statments {
2. public
static void main(String args[])
3. {
4. int
x = 2;
5. int
y = 0;
6. for
( ; y < 10; ++y) {
7. if
(y % x == 0)
8. continue;
9. else
if (y == 8)
10. break;
11. else
12. System.out.print(y
+ " ");
13. }
14. }
15. }
a) 1 3 5 7
b) 2 4 6 8
c) 1 3 5 7 9
d) 1 2 3 4 5 6 7 8 9
Answer:c
Explanation: Whenever y is divisible by x remainder
body of loop is skipped by continue statement, therefore if condition y == 8 is
never true as when y is 8, remainder body of loop is skipped by continue
statements of first if. Control comes to print statement only in cases when y
is odd.
output:
$ javac jump_statments.java
$ java jump_statments
1 3 5 7 9
9. What is the output of this program?
1. class Output {
2. public
static void main(String args[])
3. {
4. int
x, y = 1;
5. x
= 10;
6. if
(x != 10 && x / 0 == 0)
7. System.out.println(y);
8. else
9. System.out.println(++y);
10. }
11. }
a) 1
b) 2
c) Runtime error owing to division by zero in if
condition.
d) Unpredictable behavior of program.
Answer: b
Explanation: Operator short circuit and, &&,
skips evaluating right hand operand if left hand operand is false thus division
by zero in if condition does not give an error.
output:
$ javac Output.java
$ java Output
2
10. What is the output of this program?
1. class Output {
2. public
static void main(String args[])
3. {
4. int
a = 5;
5. int
b = 10;
6. first:
{
7. second:
{
8. third:
{
9. if
(a == b >> 1)
10. break
second;
11. }
12. System.out.println(a);
13. }
14. System.out.println(b);
15. }
16. }
17. }
a) 5 10
b) 10 5
c) 5
d) 10
Answer: d
Explanation: b >> 1 in if returns 5 which is
equal to a i:e 5, therefore body of if is executed and block second is exited.
Control goes to end of the block second executing the last print statement,
printing 10.
output:
$ javac Output.java
$ java Output
10
6. What is the output of this program?
1. class main_class {
2. public
static void main(String args[])
3. {
4. int
x = 9;
5. if
(x == 9) {
6. int
x = 8;
7. System.out.println(x);
8. }
9. }
10. }
a) 9
b) 8
c) Compilation error
d) Runtime error
Answer: c
Explanation: Two variables with the same name can’t be
created in a class.
output:
$ javac main_class.java
Exception in thread “main” java.lang.Error: Unresolved
compilation problem:
Duplicate local variable x
7. Which of the following statements is correct?
a) Public method is accessible to all other classes in
the hierarchy
b) Public method is accessible only to subclasses of
its parent class
c) Public method can only be called by object of its
class.
d) Public method can be accessed by calling object of
the public class.
Answer: a
8. What is the output of this program?
1. class box {
2. int width;
3. int
height;
4. int
length;
5. }
6. class mainclass {
7. public
static void main(String args[])
8. {
9. box
obj = new box();
10. obj.width
= 10;
11. obj.height
= 2;
12. obj.length
= 10;
13. int
y = obj.width * obj.height * obj.length;
14. System.out.print(y);
15. }
16. }
a) 12
b) 200
c) 400
d) 100
Answer: b
output:
$ javac mainclass.java
$ java mainclass
200
9. What is the output of this program?
1. class box {
2. int width;
3. int
height;
4. int
length;
5. }
6. class mainclass {
7. public
static void main(String args[])
8. {
9. box
obj1 = new box();
10. box
obj2 = new box();
11. obj1.height
= 1;
12. obj1.length
= 2;
13. obj1.width
= 1;
14. obj2
= obj1;
15. System.out.println(obj2.height);
16. }
17. }
a) 1
b) 2
c) Runtime error
d) Garbage value
Answer: a
Explanation: When we assign an object to another
object of same type, all the elements of right side object gets copied to
object on left side of equal to, =, operator.
output:
$ javac mainclass.java
$ java mainclass
1
10. What is the output of this program?
1. class box {
2. int width;
3. int
height;
4. int
length;
5. }
6. class mainclass {
7. public
static void main(String args[])
8. {
9. box
obj = new box();
10. System.out.println(obj);
11. }
12. }
a) 0
b) 1
c) Runtime error
d) Garbage value
Answer: d
Explanation: Object obj of box class contains
reference to the memory which was given to its class instances. Printing obj
will print the address of the memory.
output:
$ javac mainclass.java
$ java mainclass
box@130671e
6. What is the output of this program?
1. class box {
2. int width;
3. int
height;
4. int
length;
5. int
volume;
6. box() {
7. width
= 5;
8. height
= 5;
9. length
= 6;
10. }
11. void
volume() {
12. volume
= width*height*length;
13. }
14. }
15. class constructor_output {
16. public
static void main(String args[])
17. {
18. box
obj = new box();
19. obj.volume();
20. System.out.println(obj.volume);
21. }
22. }
a) 100
b) 150
c) 200
d) 250
Answer: b
output:
$ constructor_output.java
$ constructor_output
150
7. What is the output of this program?
1. class equality {
2. int x;
3. int y;
4. boolean
isequal() {
5. return(x
== y);
6. }
7. }
8. class Output {
9. public
static void main(String args[])
10. {
11. equality
obj = new equality();
12. obj.x
= 5;
13. obj.y
= 5;
14. System.out.println(obj.isequal); }
15. }
a) false
b) true
c) 0
d) 1
Answer: b
output:
$ javac Output.java
$ java Output
true
8. What is the output of this program?
1. class box {
2. int width;
3. int
height;
4. int
length;
5. int
volume;
6. void
finalize() {
7. volume
= width*height*length;
8. System.out.println(volume);
9. }
10. protected
void volume() {
11. volume
= width*height*length;
12. System.out.println(volume);
13. }
14. }
15. class Output {
16. public
static void main(String args[])
17. {
18. box
obj = new box();
19. obj.volume();
20. }
21. }
a) 150
b) 200
c) Runtime error
d) Compilation error
Answer: a
output:
$ javac Output.java
$ java Output
150
10. What is the output of this program?
1. class area {
2. int width;
3. int
length;
4. int area;
5. void
area(int width, int length) {
6. this.width
= width;
7. this.length
= length;
8. }
9.
10. }
11. class Output {
12. public
static void main(String args[])
13. {
14. area
obj = new area();
15. obj.area(5
, 6);
16. System.out.println(obj.length
+ " " + obj.width);
17. }
18. }
a) 0 0
b) 5 6
c) 6 5
d) 5 5
Answer: c
Explanation: this keyword can be used inside any
method to refer to the current object. this is always a reference to the object
on which the method was invoked.
output:
$ javac Output.java
$ java Output
6 5
6. What is the output of this program?
1. class overload {
2. int x;
3. int
y;
4. void
add(int a) {
5. x
= a + 1;
6. }
7. void
add(int a, int b){
8. x
= a + 2;
9. }
10. }
11. class Overload_methods {
12. public
static void main(String args[])
13. {
14. overload
obj = new overload();
15. int
a = 0;
16. obj.add(6);
17. System.out.println(obj.x);
18. }
19. }
a) 5
b) 6
c) 7
d) 8
Answer: c
output:
$ javac Overload_methods.java
$ java Overload_methods
7
7. What is the output of this program?
1. class overload {
2. int x;
3. int
y;
4. void
add(int a){
5. x
= a + 1;
6. }
7. void
add(int a , int b){
8. x
= a + 2;
9. }
10. }
11. class Overload_methods {
12. public
static void main(String args[])
13. {
14. overload
obj = new overload();
15. int
a = 0;
16. obj.add(6,
7);
17. System.out.println(obj.x);
18. }
19. }
a) 6
b) 7
c) 8
d) 9
Answer: c
output:
$ javac Overload_methods.java
$ java Overload_methods
8
8. What is the output of this program?
1. class overload {
2. int x;
3. double
y;
4. void
add(int a , int b) {
5. x
= a + b;
6. }
7. void
add(double c , double d){
8. y
= c + d;
9. }
10. overload()
{
11. this.x
= 0;
12. this.y
= 0;
13. }
14. }
15. class Overload_methods {
16. public
static void main(String args[])
17. {
18. overload
obj = new overload();
19. int
a = 2;
20. double
b = 3.2;
21. obj.add(a,
a);
22. obj.add(b,
b);
23. System.out.println(obj.x
+ " " + obj.y);
24. }
25. }
a) 6 6
b) 6.4 6.4
c) 6.4 6
d) 4 6.4
Answer: d
Explanation: For obj.add(a,a); ,the function in line
number 4 gets executed and value of x is 4. For the next function call, the
function in line number 7 gets executed and value of y is 6.4
output:
$ javac Overload_methods.java
$ java Overload_methods
4 6.4
9. What is the output of this program?
1. class test {
2. int a;
3. int b;
4. void
meth(int i , int j) {
5. i
*= 2;
6. j
/= 2;
7. }
8. }
9. class Output {
10. public
static void main(String args[])
11. {
12. test
obj = new test();
13. int
a = 10;
14. int
b = 20;
15. obj.meth(a
, b);
16. System.out.println(a
+ " " + b);
17. }
18. }
a) 10 20
b) 20 10
c) 20 40
d) 40 20
Answer: a
Explanation: Variables a & b are passed by value,
copy of their values are made on formal parameters of function meth() that is i
& j. Therefore changes done on i & j are not reflected back on original
arguments. a & b remain 10 & 20 respectively.
output:
$ javac Output.java
$ java Output
10 20
10. What is the output of this program?
1. class test {
2. int a;
3. int b;
4. test(int
i, int j) {
5. a
= i;
6. b
= j;
7. }
8. void
meth(test o) {
9. o.a
*= 2;
10. O.b
/= 2;
11. }
12. }
13. class Output {
14. public
static void main(String args[])
15. {
16. test
obj = new test(10 , 20);
17. obj.meth(obj);
18. System.out.println(obj.a
+ " " + obj.b);
19. }
20. }
a) 10 20
b) 20 10
c) 20 40
d) 40 20
Answer: b
Explanation: class objects are always passed by
reference, therefore changes done are reflected back on original arguments.
obj.meth(obj) sends object obj as parameter whose variables a & b are
multiplied and divided by 2 respectively by meth() function of class test. a
& b becomes 20 & 10 respectively.
output:
$ javac Output.java
$ java Output
20 10
6. What is the output of this program?
1. class string_demo {
2. public
static void main(String args[])
3. {
4. String
obj = "I" + "like" + "Java";
5. System.out.println(obj);
6. }
7. }
a) I
b) like
c) Java
d) IlikeJava
Answer: d
Explanation: Java defines an operator +, it is used to
concatenate strings.
output:
$ javac string_demo.java
$ java string_demo
IlikeJava
7. What is the output of this program?
1. class string_class {
2. public
static void main(String args[])
3. {
4. String
obj = "I LIKE JAVA";
5. System.out.println(obj.charAt(3));
6. }
7. }
a) I
b) L
c) K
d) E
Answer: a
Explanation: charAt() is a method of class String
which gives the character specified by the index. obj.charAt(3) gives 4th
character i:e I.
output:
$ javac string_class.java
$ java string_class
I
8. What is the output of this program?
1. class string_class {
2. public
static void main(String args[])
3. {
4. String
obj = "I LIKE JAVA";
5. System.out.println(obj.length());
6. }
7. }
a) 9
b) 10
c) 11
d) 12
Answer: c
output:
$ javac string_class.java
$ java string_class
11
9. What is the output of this program?
1. class string_class {
2. public
static void main(String args[])
3. {
4. String
obj = "hello";
5. String
obj1 = "world";
6. String
obj2 = obj;
7. obj2
= " world";
8. System.out.println(obj
+ " " + obj2);
9. }
10. }
a) hello hello
b) world world
c) hello world
d) world hello
Answer: c
output:
$ javac string_class.java
$ java string_class
hello world
10. What is the output of this program?
1. class string_class {
2. public
static void main(String args[])
3. {
4. String
obj = "hello";
5. String
obj1 = "world";
6. String
obj2 = "hello";
7. System.out.println(obj.equals(obj1)
+ " " + obj.equals(obj2));
8. }
9. }
a) false false
b) true true
c) true false
d) false true
Answer: d
Explanation: equals() is method of class String, it is
used to check equality of two String objects, if they are equal, true is
retuned else false.
output:
$ javac string_class.java
$ java string_class
false true
6. What is the output of this program?
1. class A {
2. int i;
3. void
display() {
4. System.out.println(i);
5. }
6. }
7. class B extends A {
8. int j;
9. void
display() {
10. System.out.println(j);
11. }
12. }
13. class inheritance_demo {
14. public
static void main(String args[])
15. {
16. B
obj = new B();
17. obj.i=1;
18. obj.j=2;
19. obj.display();
20. }
21. }
a) 0
b) 1
c) 2
d) Compilation Error
Answer: c
Explanation: class A & class B both contain
display() method, class B inherits class A, when display() method is called by
object of class B, display() method of class B is executed rather than that of
Class A.
output:
$ javac inheritance_demo.java
$ java inheritance_demo
2
7. What is the output of this program?
1. class A {
2. int i;
3. }
4. class B extends A {
5. int j;
6. void
display() {
7. super.i
= j + 1;
8. System.out.println(j
+ " " + i);
9. }
10. }
11. class inheritance {
12. public
static void main(String args[])
13. {
14. B
obj = new B();
15. obj.i=1;
16. obj.j=2;
17. obj.display();
18. }
19. }
a) 2 2
b) 3 3
c) 2 3
d) 3 2
Answer: c
output:
$ javac inheritance.java
$ java inheritance
2 3
8. What is the output of this program?
1. class A {
2. public int
i;
3. private
int j;
4. }
5. class B extends A {
6. void
display() {
7. super.j
= super.i + 1;
8. System.out.println(super.i
+ " " + super.j);
9. }
10. }
11. class inheritance {
12. public
static void main(String args[])
13. {
14. B
obj = new B();
15. obj.i=1;
16. obj.j=2;
17. obj.display();
18. }
19. }
a) 2 2
b) 3 3
c) Runtime Error
d) Compilation Error
Answer: d
Explanation: class contains a private member variable
j, this cannot be inherited by subclass B and does not have access to it.
output:
$ javac inheritance.java
Exception in thread “main” java.lang.Error: Unresolved
compilation problem:
The field A.j is not visible
9. What is the output of this program?
1. class A {
2. public int
i;