3.
Java Exam Preparation Practice Test - MCQ
1.
Consider the following code , what is the output
provided a valid file name is given on the command
prompt?
class Q006{
public static void main(String args[]){
boolean flag = false;
if ( flag = true) {
import java.io.*;
class Q032{
public static void main(String args[]) throws Exception{
FileInputStream fin;
int c = 0;
try {
fin = new FileInputStream(args[0]);
while ((c = fin.read()) != -1) {
System.out.print((char)c);
}
} catch (Exception e) {
System.out.println(e);
}
fin.close();
}
}
System.out.println(“true”);
}
if ( flag == false) {
System.out.println(“false”);
}
}
}
Options :
a. true
b. false
c. Compile-time error " Q006.java: Incompatible type
for declaration. Can't convert boolean to
java.lang.Boolean. "
d. true
false
Options :
a. Compile-time error " Variable fin may not have
been initialized."
b. Run-time exception "
java.lang.ArrayIndexOutOfBoundsException: 0"
c. Run's fine displaying the contents of the file .
d. Compile-time error " Undefined variable: args"
2.
What is the output ?
4.
What is the output ?
class A{
A() {
System.out.print("1");
}
What is the output for the following:
}
class A{
class Q005 extends A{
Q005() {
System.out.print("2");
}
public static void main(String args[]) {
Q005 obj = new Q005();
System.out.println("3");
}
}
static int i;
A(){
++i;
}
private int get(){
return ++i;
}
}
class B extends A{
B(){
i++;
}
int get(){
return ( i + 3);
}
}
Options :
a. 123
b. 23
c. 3
d. 1 , 2 , 3 each on a separate line
6.
Predict the output:
class Q008{
public static void main(String args[]){
int i = -1;
System.out.println((i<0)?-i:i);
}
}
class Q028 extends B{
public static void main(String ka[]){
Q028 obj = new Q028();
A ob_a = new A();
ob_a = (A)obj;
System.out.println(ob_a.get());
}
}
Options :
a. 2
b. Compile error " No method matching get() found in
class Q026."
c. 5
d. NullPointerException thrown at run-time .
Options :
a. 1
b. -1
c. Compile error
d. Run-time error
1
7.
8.
Will the following compile? If yes what is the output?
10.
class Q009{
public static void main(String args[]){
System.out.println(
(Math.abs(Integer.MIN_VALUE)));
//For Your Information,
//Integer.MIN_VALUE = -2147483648
}
}
class Test{
static boolean flag;
public static void main(String args[]){
if (flag) {
System.out.println(flag);
}
}
}
Options :
a. 2147483648
b. Compile Error
c. -2147483648
d. NegativeArraySizeException thrown at runtime
Options :
a. Compiler error, boolean flag: variable flag may not
have been initialized
b. Compiler error, System.out.println (flag): can't
convert boolean to String
c. true
d. false
e. Compiles & runs fine with no output generated
Will the following code compile? If yes , what is the
output?
class Q012 {
Q012(int i) {
System.out.println(i);
this.i = i;
}
11.
What is the output when Test01 class is run?
class A {
A() {
//some initialization
}
void do_something(){
System.out.println("I'm in A");
}
public static void main(String ka[]) {
Q012 obj = new Q012(10);
}
}
}
class B extends A {
B() {
//some initialization
}
void do_something() {
System.out.println("I'm in B");
}
}
class Test01{
public static void main(String args[]){
A a = new B();
a.do_something();
}
}
Options :
a. 0
b. 10
c. null
d. Compile error "Q012.java:10: No variable i defined
in class Q012. "
9.
What is the output for this piece?
What is the output of this code?
class Q011{
int i;
Q011(int i){
System.out.println(i);
this.i = i;
}
Options :
a. I'm in A
b. I'm in B
c. Compiler error , A a = new B ( ) : Explicit cast
needed to convert A to B
d. ClassCastException thrown at runtime
public static void main(String ka[]){
Q011 obj = new Q011(10);
System.out.println(obj.i);
}
}
12.
Options :
a. 10
10
b. Compile error " Q012.java:16: Variable i may not
have been initialized. "
c. 0
10
d. 10
0
What is the output for the following code?
class Q014{
public String get(int i){return null;}
public static void main(String ka[]){
System.out.println((new Q014()).get(1));
}
}
Options :
a. 0
b. NullPointerException at run-time
c. Compile error
d. null
2
13.
What is the output?
16.
class Q018 {
static Object obj;
static String get() {
return null;
}
What is the output?
class Test02 {
public String fetch() {
return null;
}
public static void main(String args[]){
System.out.println(
(Q018.get()) == (Q018.obj));
}
public static void main(String args[]) {
Test02 obj = new Test02();
String str = obj.fetch();
System.out.println((str+"").toString());
}
}
}
Options :
a. Compile error
b. Run-time error
c. true
d. false
14.
Options :
a. null
b. Compiler error , can't invoke a method on null
c. NullPointerException thrown at runtime
d. ClassCastException thrown at runtime
What is the output?
17.
class Q015{
public String get(int i){
return null;
}
class Q022 {
public static void main(String ka[]) {
while(false) {
System.out.println("Great");
}
}
}
public static void main(String ka[]){
Q015 obj = new Q015();
Object i = obj.get(10);
System.out.println(i.toString());
}
Options :
a. Run's with no output
b. Run-time error "Statement not reached."
c. Great
d. Compiler error, System.out.println ( "Great"):
statement not reached
}
Options :
a. null
b. NullPointerException at run-time
c. Compile error
d. 0
15.
What is the output?
18.
What is the output?
What is the output?
class A{
static int i;
private int get(){
return 1;
}
class Q013{
int i;
Q013(int i){
System.out.println(i);
}
}
class B extends A{
private int get(){
return 2;
}
}
class Q027 extends B{
public static void main(String ka[]) {
Q027 obj = new Q027();
System.out.println(obj.get());
}
}
public static void main(String ka[]) {
Q013 obj = new Q013(10);
System.out.println(obj.i);
}
}
Options :
a. 10
10
b. Compile error , System.out.println (obj.i):
variable i may not have been initialized
c. 0
10
d. 10
0
Options :
a. 2
b. Compile error , System.out.println (obj.get ( )): no
method matching get( ) found in class Q027
c. 1
d. 2
e. NullPointerException thrown at run-time .
3
19.
What is the output?
23.
Will the output from the following two code snippets
be any different?
Snippet 1 :
for ( int i = 0 ; i < 5 ; i++ ) {
System.out.println(i);
}
Snippet 2 :
for ( int i = 0 ; i < 5 ; ++i ) {
System.out.println(i);
}
Options :
a. yes
b. no
24.
What is the output of the following code?
class Q029{
public static void main(String args[]){
boolean b[] = new boolean[2];
System.out.println(b[1]);
}
}
Options :
a. Compile error " Variable b may not have been
initialized."
b. Run-time error " Variable b may not have been
initialized."
c. false
d. true
21.
class Q009{
public static void main(String args[]) {
float f = 1/2;
System.out.println(f);
}
}
Will the following code compile? If yes choose the
most correct two options.
class Q011 {
public static void main(String args[]) {
char a = 'a' + 2;
System.out.println(a);
int i = 2;
char c = 'a' + i; //---1
System.out.println(c); //---2
}
}
Options :
a. Compile-time error float f = 1/2 : explicit cast
needed to convert int to float
b. 0.0
c. 0.5
d. ClassCastException thrown at run-time
Options :
a. Compile-time error "Explicit cast needed to
convert int to char"
b. The code can be made to compile by
commenting out lines marked as 1 & 2
c. The code can be made to compile by
commenting out the line "char a = 'a' + 2;"
d. The output is:
67
67
22.
25.
What is the output for the following code?
class Torment{
int i = 2;
public static void main(String args[]) {
int i = 12;
System.out.println(i);
}
}
Options :
a. Compiler error, System.out.println(i) : can't make a
static reference to a non static variable i
b. Output = 2
c. Output = 12
d. Compiler error, i = 12 : variable i is already defined
in this class
What is the output ? FYI ( int ) ' A ' = 65
class Q1{
public static void main(String args[]){
byte b = 65;
switch (b) {
case 'A':
System.out.println("A");
break;
case 65:
System.out.println("65");
break;
default:
System.out.println("default");
}
}
}
29.
Options :
a. A
b. 65
c. Compile time error, case 65: duplicate case label
d. Runtime error "Duplicate case label: 65"
e. default
4
Will the following class compile ? If yes, what is the
output ?
class Envy{
static int i;
Envy(){ ++i; }
public static void main(String args[]) {
System.out.println(i);
}
}
Options :
a. Yes , it compiles but NullPointerException thrown
at runtime
b. Compiler error, System.out.println(i) : variable i
may not have been initialized
c. Yes it compiles & output = 0
d. Yes it compiles & the output = 1
e. Compiler error, ++ i : can't make a non-static
reference to a static variable , i
27.
Consider the following class . Which of the marked
lines need to be commented out for the class to
compile correctly?
33.
class Evolve {
static int i = 1;
static int j = 2;
int x = 3;
static int y = 6;
class Test02{
public static void main(String args[]){
String str = args[0];
switch ( str.equals("just")) {
case 1:
System.out.println("case 1");
break;
case 2:
System.out.println("case 2");
break;
default:
break;
}
}
}
public static void main(String args[]) {
System.out.println(i + j); //---1
System.out.println(x + i); //---2
System.out.println(i + y); //---3
System.out.println(x + j); //---4
}
}
Options :
a. 1 & 2
b. 1, 2 & 4
c. 3 & 4
d. 2 & 4
e. 1, 2 & 3
30.
32.
Options :
a. Output = case 1
b. Output = case 2
c. No output generated
d. Compiler error, switch(str.equals("just")) : Can't
convert boolean to int.
e. Compiler error, case 1 : can't convert boolean to int
Choose all the valid declarations for the main method
from the list below.
a. public void main(String args[])
b. static void main(String args[])
c. public static void main(String[] ka)
d. static public void main(String[] args)
e. public static void main(String ka[])
34.
What is the output of the following code fragment
when run with the following command line - java 1 ?
class Test03{
public static void main(String args[]) {
int i = Integer.parseInt(args[0]);
switch (i) {
case 1:
System.out.println("case 1");
case 2:
System.out.println("case 2");
default:
System.out.println("default");
break;
}
}
}
What is the compiler error generated by the
following piece of code or what is the output if any?
class Test01{
public static void main(String args[]){
int i = 1;
if ( i = 2 ) {
System.out.println("In if");
} else System.out.println("In else");
}
}
Options :
a. Output = In If
b. Compiles but no output is generated
c. Output is = In else
d. Compiler error, if (i=2) : can't convert int to boolean
37.
Will the code given below compile? If run with the
following command line - java just - what is the
output?
Options :
a. case 1
case2
default
b. case 1
c. Runtime exception thrown NumberFormatException, Integer.parseInt(args[0] ):
Can't convert String to int
d. The code won't compile because there is no method
parseInt( ) defined in the Integer class .
What is the output for this?
class Test06{
public static void main(String args[]){
for (int i = 0 ; i < 5 ; i++) {
System.out.println(i); break;
}
}
}
Options :
a. 0 to 5, each on a separate line
b. 1 to 5, each on a new line
c. 1 to 4 each on a new line
d. 0
e. 0 to 4, each on a new line
5
35.
Predict the output for the following piece of code.
40.
class Test04{
public static void main(String args[]){
for ( int i = 1 ; i <= 5 ; i++ ) {
if ( i < 5 ) {
continue;
} else System.out.println( i );
}
}
}
class Test09 {
static int tomb(char a) {
throw new NumberFormatException();
}
public static void main(String args[]) {
try {
tomb('a');
} catch (Exception e) {
System.out.println("Done");
}
}
Options :
a. 1 to 5 are printed on a new line each
b. 1 to 4 are printed on a new line each
c. Only 5 is printed
d. 2 to 5 are printed on a new line each
e. 2 to 4 are printed on a new line each
f. No output is generated because continue terminates
the loop
36.
}
Options:
a. NumberFormatException thrown at runtime
b. Compiler error , throw new
NumberFormatException() : Checked Exceptions
must be declared in the throws clause or must be
caught in the corresponding catch block
c. Compiler error, System.out.println("Done") :
statement not reached
d. Output = Done
Will the following code block compile? If yes , what is
the output?
class Test05{
public static void main(String args[]){
try {
throw new Exception();
System.out.println("try");
} catch (Exception e) {
System.out.println("catch");
} finally {
System.out.println("finally");
}
}
}
Options :
a. try
catch
finally
b. catch
finally
c. finally
d. Exception must be declared in the throws clause
e. Compiler error, System.out.println("try"): statement
not reached
38.
Does the following piece of code compile? If yes ,
what is the output?
Will the following code generate a compiler error? If
not , what is the output?
class Test07{
public static void main(String args[]){
for (int i = 0 ; i < 5 ; i++) {
break;
System.out.println(i);
}
}
}
Options :
a. 0 to 5 , each on a separate line
b. 1 to 5 , each on a new line
c. 1 to 4 each on a new line
d. 0
e. Compiler error , System.out.println ( i ) : statement
not reached
f. 0 to 4 , each on a new line
6
41.
What will happen when you invoke the following
method?
void infiniteLoop ( ) {
byte b = 1 ;
while (++b > 0) ;
System.out.println ("Welcome to Java") ;
}
Options :
a. The loop never ends ( infinite loop ) .
b. Prints " Welcome to Java " to the console
c. Compilation error at line 5. ++ operator should not
be used for byte type variables.
d. Prints nothing but terminates after some time
42.
What is the output of the following code ?
class A{
static int i;
A(){ ++i; }
int get(){ return ++i; }
}
class B extends A{
private B(){ i++; }
int get(){ return ( i + 3); }
}
class Q028 extends B{
public static void main(String ka[]) {
Q028 obj = new Q028();
A ob = new A();
ob = (A)obj;
System.out.println(ob.get());
}
}
Options:
a. 2
b. Compile error " No method matching get( ) found in
class Q026."
c. 5
d. NullPointerException thrown at run-time .
Answers:
1. a
2. b
3. a
4. a
5. c
6. a
7. c
8. d
9. a
10. e
11. b
12. d
13. c
14. b
15. d
16. a
17. d
18. b
19. c
20. e
21. a & b
22. c
23. b
24. b
25. c
26. b
27. d
28. e
29. c
30. c , d & e
31. d
32. d
33. d
34. a
35. c
36. e
37. d
38. e
39. c
40. d
41. b
42. c
7