JAVA(Operators / Classes Interview Questions)
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1) What are operators and what are the various types of operators
available in Java?
Ans: Operators are special symbols used in expressions.
The following are the types of operators:
Arithmetic operators,
Assignment operators,
Increment & Decrement operators,
Logical operators,
Biwise operators,
Comparison/Relational operators and
Conditional operators
2) The ++ operator is used for incrementing and the -- operator is used
for
decrementing.
a)True
b)False
Ans: a.
3) Comparison/Logical operators are used for testing and magnitude.
a)True
b)False
Ans: a.
4) Character literals are stored as Unicode characters.
a)True
b)False
Ans: a.
5) What are the Logical operators?
Ans: OR(|), AND(&), XOR(^) AND NOT(~).
6) What is the % operator?
Ans : % operator is the modulo operator or reminder operator. It
returns the reminder of dividing the first operand by second operand.
7) What is the value of 111 % 13?
3
5
7
9
Ans : c.
Operators in Java -2
8) Is &&= a valid operator?
Ans : No.
9) Can a double value be cast to a byte?
Ans : Yes
10) Can a byte object be cast to a double value ?
Ans : No. An object cannot be cast to a primitive value.
11) What are order of precedence and associativity?
Ans : Order of precedence the order in which operators are evaluated in
expressions.
Associativity determines whether an expression is evaluated left-right
or right-left.
12) Which Java operator is right associativity?
Ans : = operator.
13) What is the difference between prefix and postfix of -- and ++
operators?
Ans : The prefix form returns the increment or decrement operation and
returns the value of the increment or decrement operation.
The postfix form returns the current value of all of the expression and
then
performs the increment or decrement operation on that value.
14) What is the result of expression 5.45 + "3,2"?
The double value 8.6
The string ""8.6"
The long value 8.
The String "5.453.2"
Ans : d
15) What are the values of x and y ?
x = 5; y = ++x;
Ans : x = 6; y = 6
16) What are the values of x and z?
x = 5; z = x++;
Ans : x = 6; z = 5
Control Statements
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1) What are the programming constructs?
Ans: a) Sequential
b) Selection -- if and switch statements
c) Iteration -- for loop, while loop and do-while loop
2) class conditional {
public static void main(String args[]) {
int i = 20;
int j = 55;
int z = 0;
z = i < j ? i : j; // ternary operator
System.out.println("The value assigned is " + z);
}
}
What is output of the above program?
Ans: The value assigned is 20
3) The switch statement does not require a break.
a)True
b)False
Ans: b.
4) The conditional operator is otherwise known as the ternary operator.
a)True
b)False
Ans: a.
5) The while loop repeats a set of code while the condition is false.
a)True
b)False
Ans: b.
6) The do-while loop repeats a set of code atleast once before the
condition is tested.
a)True
b)False
Ans: a.
7) What are difference between break and continue?
Ans: The break keyword halts the execution of the current loop and
forces control out of the loop.
The continue is similar to break, except that instead of halting the
execution of the loop, it starts the next iteration.
8) The for loop repeats a set of statements a certain number of times
until a condition is matched.
a)True
b)False
Ans: a.
9) Can a for statement loop indefinitely?
Ans : Yes.
10) What is the difference between while statement and a do statement/
Ans : A while statement checks at the beginning of a loop to see
whether the next loop iteration should occur.
A do statement checks at the end of a loop to see whether the next
iteration of a loop should occur. The do statement will always execute
the body of a loop at least once.
Classes and Methods
---------------------------------
) Which is used to get the value of the instance variables?
Ans: Dot notation.
2) The new operator creates a single instance named class and returns a
reference to that object.
a)True
b)False
Ans: a.
3) A class is a template for multiple objects with similar features.
a)True
b)False
Ans: a.
4) What is mean by garbage collection?
Ans: When an object is no longer referred to by any variable, Java
automatically
reclaims memory used by that object. This is known as garbage
collection.
5) What are methods and how are they defined?
Ans: Methods are functions that operate on instances of classes in
which they are defined.Objects can communicate with each other using
methods and can call methods in other classes.
Method definition has four parts. They are name of the method, type of
object or primitive type the method returns, a list of parameters and
the body of the method.
A method's signature is a combination of the first three parts
mentioned above.
6) What is calling method?
Ans: Calling methods are similar to calling or referring to an instance
variable. These methods are accessed using dot notation.
Ex: obj.methodname(param1,param2)
7) Which method is used to determine the class of an object?
Ans: getClass( ) method can be used to find out what class the belongs
to. This class is defined in the object class and is available to all
objects.
8) All the classes in java.lang package are automatically imported when
a program is compiled.
a)True
b)False
Ans: a.
9) How can class be imported to a program?
Ans: To import a class, the import keyword should be used as shown.;
import classname;
10) How can class be imported from a package to a program?
Ans: import java . packagename . classname (or) import java.package
name.*;
11) What is a constructor?
Ans: A constructor is a special kind of method that determines how an
object is
initialized when created.
12) Which keyword is used to create an instance of a class?
Ans: new.
13) Which method is used to garbage collect an object?
Ans: finalize ().
14) Constructors can be overloaded like regular methods.
a)True
b)False
Ans: a.
15) What is casting?
Ans: Casting is bused to convert the value of one type to another.
16) Casting between primitive types allows conversion of one primitive
type to another.
a)True
b)False
Ans: a.
17) Casting occurs commonly between numeric types.
a)True
b)False
Ans: a.
18) Boolean values can be cast into any other primitive type.
a)True
b)False
Ans: b.
19) Casting does not affect the original object or value.
a)True
b)False
Ans: a.
20) Which cast must be used to convert a larger value into a smaller
one?
Ans: Explicit cast.
21) Which cast must be used to cast an object to another class?
Ans: Specific cast.
22) Which of the following features are common to both Java & C++?
A.The class declaration
b.The access modifiers
c.The encapsulation of data & methods with in objects
d.The use of pointers
Ans: a,b,c.
23) Which of the following statements accurately describe the use of
access modifiers within a class definition?
a.They can be applied to both data & methods
b.They must precede a class's data variables or methods
c.They can follow a class's data variables or methods
d.They can appear in any order
e.They must be applied to data variables first and then to methods
Ans: a,b,d.
24) Suppose a given instance variable has been declared private.
Can this instance variable be manipulated by methods out side its
class?
a.yes
Ans: b.
sn nithya
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