OCJP Certification Sample Question Set-3

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OCJP Certification Sample Question Set-3

Operator related

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.

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 statement Related:

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 indefintely?
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.

Utility Class related:

1) What is the Vector class?

ANSWER : The Vector class provides the capability to implement a growable array of objects.

2) What is the Set interface?

ANSWER : The Set interface provides methods for accessing the elements of a finite mathematical set.Sets do not allow duplicate elements.

3) What is Dictionary class?

ANSWER : The Dictionary class is the abstarct super class of Hashtable and Properties class.Dictionary provides the abstarct functions used to store and retrieve objects by key-value.This class allows any object to be used as a key or value.

4) What is the Hashtable class?

ANSWER : The Hashtable class implements a hash table data structure. A hash table indexes and stores objects in a dictionary using hash codes as the objects’ keys. Hash codes are integer values that identify objects.

5) What is the Properties class?

Answer : The properties class is a subclass of Hashtable that can be read from or written to a stream.It also provides the capability to specify a set of default values to be used if a specified key is not found in the table. We have two methods load() and save().

6) What changes are needed to make the following prg to compile?

import java.util.*;
class Ques{
public static void main (String args[]) {
String s1 = “abc”;
String s2 = “def”;
Vector v = new Vector();
String s3 = v.elementAt(0) + v.elementAt(1);
System.out.println(s3);
}
}
ANSWER : Declare Ques as public B) Cast v.elementAt(0) to a String
C) Cast v.elementAt(1) to an Object. D) Import java.lang
ANSWER : B) Cast v.elementAt(0) to a String

7) What is the output of the prg.

import java.util.*;
class Ques{
public static void main (String args[]) {
String s1 = “abc”;
String s2 = “def”;
Stack stack = new Stack();
stack.push(s1);
stack.push(s2);
try{
String s3 = (String) stack.pop() + (String) stack.pop() ;
System.out.println(s3);
}catch (EmptyStackException ex){}
}
}
ANSWER : abcdef B) defabc C) abcabc D) defdef

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