Questions and answers for exam Preparation

MCQs

Total Questions : 105 | Page 4 of 11 pages

What is the output of this program?

import java.util.*;
class vector {
public static void main(String args[]) {
Vector obj = new Vector(4,2);
obj.addElement(new Integer(3));
obj.addElement(new Integer(2));
obj.addElement(new Integer(5));
obj.removeAll(obj);
System.out.println(obj.isEmpty());
}
}

0
1
true
false

Discuss Question

Answer: Option C. -> true

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

Question 32.

What is the output of this program?

import java.util.*;
class hashtable {
public static void main(String args[]) {
Hashtable obj = new Hashtable();
obj.put("A", new Integer(3));
obj.put("B", new Integer(2));
obj.put("C", new Integer(8));
System.out.print(obj.toString());
}
}

{C=8, B=2}
[C=8, B=2]
{A=3, C=8, B=2}
[A=3, C=8, B=2]

Discuss Question

Answer: Option C. -> {A=3, C=8, B=2}

obj.toString returns String equivalent of the hashtable, which can also be obtained by

simply writing System.out.print(obj); as print system automatically coverts the obj to

string equivalent.
Output:
$ javac hashtable.java
$ java hashtable
{A=3, C=8, B=2}

Question 33.

What is the output of this program?

import java.util.*;
class date {
public static void main(String args[]) {
Date obj = new Date();
System.out.print(obj);
}
}

Prints Present Date
Runtime Error
Any Garbage Value
Prints Present Time & Date

Discuss Question

Answer: Option D. -> Prints Present Time & Date

None.
Output:
$ javac date.java
$ java date
Tue Jun 11 11:29:57 PDT 2013

Question 34.

What is the output of this program?

import java.util.*;
class Output {
public static void main(String args[]) {
ArrayList obj = new ArrayList();
obj.add("A");
obj.add(0, "B");
System.out.println(obj.size());
}
}

0
1
2
Any Garbage Value

Discuss Question

Answer: Option C. -> 2

None.
Output:
$ javac Output.java
$ java Output
2

Question 35.

What is the output of this program?

class access{
static int x;
void increment(){
x++;
}
}
class static_use {
public static void main(String args[])
{
access obj1 = new access();
access obj2 = new access();
obj1.x = 0;
obj1.increment();
obj2.increment();
System.out.println(obj1.x + " " + obj2.x);
}
}

1 2
1 1
2 2
Compilation Error

Discuss Question

Answer: Option C. -> 2 2

All objects of class share same static variable, all the objects share same copy of static members,

obj1.x and obj2.x refer to same element of class which has been incremented twice and its value is 2.
output:
$ javac static_use.java
$ java static_use
2 2

Question 36.

What is the output of this program?

import java.util.*;
class Array {
public static void main(String args[]) {
int array[] = new int [5];
for (int i = 5; i > 0; i--)
array[5 - i] = i;
Arrays.sort(array);
for (int i = 0; i < 5; ++i)
System.out.print(array[i]);;
}
}

12345
54321
1234
5432

Discuss Question

Answer: Option B. -> 54321

Arrays.sort(array) method sorts the array into 1,2,3,4,5.
Output:
$ javac Array.java
$ java Array
12345

Question 37.

What is the output of this program?

import java.util.*;
class Linkedlist {
public static void main(String args[]) {
LinkedList obj = new LinkedList();
obj.add("A");
obj.add("B");
obj.add("C");
obj.removeFirst();
System.out.println(obj);
}
}

[A, B]
[B, C]
[A, B, C, D]
[A, B, C]

Discuss Question

Answer: Option B. -> [B, C]

None.
Output:
$ javac Linkedlist.java
$ java Linkedlist
[B, C]

Question 38.

What is the output of this program?

class Output {
public static void main(String args[]) {
int x = 3.14;
int y = (int) Math.abs(x);
System.out.print(y);
}
}

Discuss Question

Answer: Option B. -> 3

None.
Output:
$ javac Output.java
$ java Output
3

Question 39.

What is the output of this program?

import java.util.*;
class Maps {
public static void main(String args[]) {
HashMap obj = new HashMap();
obj.put("A", new Integer(1));
obj.put("B", new Integer(2));
obj.put("C", new Integer(3));
System.out.println(obj.keySet());
}
}

[A, B, C]
{A, B, C}
{1, 2, 3}
[1, 2, 3]

Discuss Question

Answer: Option A. -> [A, B, C]

keySet() method returns a set containing all the keys used in the invoking map. Here

keys are characters A, B & C. 1, 2, 3 are the values given to these keys.
Output:
$ javac Maps.java
$ java Maps
[A, B, C]

Question 40.

What is the output of this program?

import java.util.*;
class vector {
public static void main(String args[]) {
Vector obj = new Vector(4,2);
obj.addElement(new Integer(3));
obj.addElement(new Integer(2));
obj.addElement(new Integer(5));
obj.insertElementAt(new Integer(8), 2);
System.out.println(obj);
}
}