Java Certification Quiz: Online Test

Java Certification Quiz

Instructions For Quiz
- This Mock Test has 60 Questions
- Each Question is of 1 marks so total 60 marks
- MCQ(Multiple Choice Questions) with only ONE valid answer
Name
Email*
Get Result on your Email address

1)What gets printed on the standard output when the class below is compiled and executed. Select the one correct answer.

public class ShortCkt
{
public static void main(String args[])
{
int i = 0;
boolean t = true;
boolean f = false, b;
b = (t | ((i++) == 0));
b = (f | ((i+=2) > 0));
System.out.println(i);
}
}
01234

2) What gets displayed on the screen when the following program is compiled and run. Select the one correct answer.

public class test
{
public static void main(String args[])
{
boolean x = true;
int a;
if(x) a = x ? 1: 2;
else a = x ? 3: 4;
System.out.println(a);
}
}
1234none

3)What is the result when this code is executed?

class One {
public One() { System.out.print(1); }
}
class Two extends One {
public Two() { System.out.print(2); }
}
class Three extends Two {
public Three() { System.out.print(3); }
}
public class Numbers{
public static void main( String[] argv ) { new Three(); }
}
13123321The code runs with no output

4) What is the result?

class TestA
{
public void start()
{
System.out.println("TestA");
}
}
public class TestB extends TestA
{
public void start()
{
System.out.println("TestB");
}
public static void main(String[] args)
{
((TestA)new TestB()).start();
}
}
TestATestBCompilation fails.An exception is thrown at runtime.none

5)What is the number of bytes used by Java primitive long. Select the one correct answer.*

The number of bytes is compiler dependent.24864

6)What is the result of evaluating the expression 14 ^ 23. Select the one correct answer.*

253763117

7)What all gets printed when the following program is compiled and run. Select the one correct answer.

public class test
{
public static void main(String args[])
{
int i=0, j=2;
do
{
i=++i;
j--;
}
while(j>0);
System.out.println(i);
}
}
012The program does not compile because of statement "i=++i;"

8)What all gets printed when the following gets compiled and run.

public class test {
public static void main(String args[]) {
String s1 = "abc";
String s2 = new String("abc");

if(s1 == s2)
System.out.println(1);
else
System.out.println(2);
if(s1.equals(s2))
System.out.println(3);
else
System.out.println(4);
}
}
12323

9)Which declaration of the main method below would allow a class to be started as a standalone program. Select the one correct answer.*

public static int main(char args[])public static void main(String args[])public static void MAIN(String args[])public static void main(String args)public static void main(char args[])

10)What is the result?

public static void main(String[] args)
{
12. Integer i = new Integer(1) + new Integer(2);
switch(i)
{
case 3: System.out.println("three"); break;
15. default: System.out.println("other"); break;
}
}
threeotherAn exception is thrown at runtime.Compilation fails because of an error on line 12Compilation fails because of an error on line 15.

11)Which exception or error should be thrown by the virtual machine?

public class ClassA
{
public void count(int i)
{
count(++i);
}
}
And:
ClassA a = new ClassA();
a.count(3);
StackOverflowErrorNullPointerExceptionNumberFormatExceptionIllegalArgumentExceptionExceptionInInitializerError

12)What is the result?

public static void test(String str)
{
int check = 4;
if (check = str.length())
{
System.out.print(str.charAt(check -= 1) +", ");
}
else
{
System.out.print(str.charAt(0) + ", ");
}
}
and the invocation:
21. test("four");
22. test("tee");
test("to");
r, t, t,r, e, o,Compilation fails.An exception is thrown at runtime.

13)How many String objects will be created when this method is invoked?

public String makinStrings()
{
String s = “Fred”;
s = s + “47”;
s = s.substring(2, 5);
s = s.toUpperCase();
return s.toString();
}
12345
14)What is the result?

public static void parse(String str)
{
try
{
float f = Float.parseFloat(str);
}
catch (NumberFormatException nfe)
{
f = 0;
}
finally
{
System.out.println(f);
}
}
public static void main(String[] args)
{
parse("invalid");
}
0Compilation fails.A ParseException is thrown by the parse method at runtimeA NumberFormatException is thrown by the parse method at runtime.

15)What is the result?

static void test() throws Error
{
if (true) throw new AssertionError();
System.out.print("test ");
}
public static void main(String[] args)
{
try
{
test();
}
catch (Exception ex)
{
System.out.print("exception ");
}
System.out.print("end ");
}
endCompilation fails.exception endexception test endA Throwable is thrown by main

16)What is the result?

static void test() throws RuntimeException
{
try
{
System.out.print("test ");
throw new RuntimeException();
}
catch (Exception ex)
{
System.out.print("exception ");
}
}
public static void main(String[] args)
{
try
{
test();
}
catch (RuntimeException ex)
{
System.out.print("runtime ");
}
System.out.print("end ");
}
test endCompilation fails.test runtime endtest exception endA Throwable is thrown by main at runtime.

16)What is the result?

static void test()
{
try
{
String x = null;
System.out.print(x.toString() + " ");
}
finally { System.out.print("finally "); }
}
public static void main(String[] args)
{
try { test(); }
catch (Exception ex) { System.out.print("exception "); }
}
nullfinallynull finallyCompilation fails.finally exception

18)What is the result?

public enum Title
{
MR("Mr."), MRS("Mrs."), MS("Ms.");
private final String title;
private Title(String t)
{ title = t; }
public String format(String last, String first)
{
return title + " " + first + " " + last;
}
}
public static void main(String[] args)
{
System.out.println(Title.MR.format("Doe", "John"));
}
Mr. John DoeAn exception is thrown at runtime.Compilation fails because of an error in line 12.Compilation fails because of an error in line 15.Compilation fails because of an error in line 20

19)Which of the following are NOT keywords or reserved words in Java?*

ifwhilegotoThen

20)Given:public class Ball{ public enum Color { RED, GREEN, BLUE }; public void foo() { insert code here { System.out.println(c); } }}Which code inserted at line 14 causes the foo method to print RED, GREE*

for( Color c : Color.values() )for( Color c = RED; cfor( Color c ; c.hasNext() ; c.next() )for( Color c = Color[0]; cfor( Color c = Color.RED; c

21)What is the result when the programmer attempts to compile the code and run it with the command java Converter 12?

class Converter
{
public static void main(String[] args)
{
Integer i = args[0];
int j = 12;
System.out.println("It is " + (j==i) + " that j==i.");
}
}
It is true that j==i.It is false that j==i.An exception is thrown at runtime.Compilation fails because of an error in line 13.

22)What is the output?

class Cup { }
class PoisonCup extends Cup { } public void takeCup(Cup c)
{
if (c instanceof PoisonCup)
{
System.out.println("Inconceivable!");
}
else if (c instanceof Cup)
{
System.out.println("Dizzying intellect!");
}
else
{
System.exit(0);
}
}
And the execution of the statements:
Cup cup = new PoisonCup();
takeCup(cup);
Inconceivable!Dizzying intellect!The code runs with no outputAn exception is thrown at runtime

23)What is the result?

public class Yippee2
{
static public void main(String [] yahoo)
{
for(int x = 1; x < yahoo.length; x++)
{
System.out.print(yahoo[x] + " ");
}
}
}
and the command line invocation:
java Yippee2 a b c
a bb ca b cCompilation fails.E. An exception is thrown at runtime

24)Which code, inserted at line 14, allows the Sprite class to compile?

class Nav
{
public enum Direction
{
NORTH, SOUTH, EAST, WEST
}
}
public class Sprite
{
Line 14. // insert code here
}
Direction d = NORTH;Nav.Direction d = NORTH;Direction d = Direction.NORTH;Nav.Direction d = Nav.Direction.NORTH;none

25)What is required at line 5 in class SomeApp to use the process method of BitUtils?

Given classes defined in two different files:
package util;
public class BitUtils
{
public static void process(byte[])
{
/* more code here */
}
}
package app;
public class SomeApp
{
public static void main(String[] args)
{
byte[] bytes = new byte[256];
// insert code here
}
}
process(bytes);BitUtils.process(bytes);util.BitUtils.process(bytes);SomeApp cannot use methods in BitUtils.import util.BitUtils.*; process(bytes);

26)Which code, inserted at line 4, guarantees that this program will output [1, 2]?

import java.util.*;
public class Example
{
public static void main(String[] args)
{
// insert code here
set.add(new Integer(2));
set.add(new Integer(1));
System.out.println(set);
}
}
Set set = new TreeSet();Set set = new HashSet();Set set = new SortedSet();List set = new SortedList();Set set = new LinkedHashSet();

27)What is the result?

public static Iterator reverse(List list)
{
Collections.reverse(list);
return list.iterator();
}
public static void main(String[] args)
{
List list = new ArrayList();
list.add("1"); list.add("2"); list.add("3");
for (Object obj: reverse(list))
System.out.print(obj + ", ");
} public class Example
3, 2, 1,1, 2, 3,Compilation fails.The code runs with no output.An exception is thrown at runtime.

28)A programmer has an algorithm that requires a java.util.List that providesan efficient implementation of add(0, object), but does NOT need to support quick random access.What supports these requirements?*

java.util.Queuejava.util.ArrayListjava.util.LinearListjava.util.LinkedListnone

29)Which code will sort this list in the opposite order of the sort in line?

List list = // more code here
Collections.sort(list, new MyComparator());
Collections.reverseSort(list, new MyComparator());Collections.sort(list, new MyComparator());list.reverse();Collections.sort(list, new InverseComparator(new MyComparator()));Collections.sort(list, Collections.reverseOrder(new MyComparator()));

30)Given:Which method will complete this class?

public class Score implements Comparable
{
private int wins, losses;
public Score(int w, int 1)
{ wins = w; losses = 1; }
public int getWins()
{ return wins; }
public int getLosses()
{ return losses; }
public String toString()
{
return “”;
}
// insert code here
}
public int compareTo(Object o) {/*mode code here*/}public int compareTo(Score other) {/*more code here*/}public int compare(Score s1,Score s2){/*more code here*/}public int compare(Object o1,Object o2){/*more code here*/}

31)programmer iterates over the TreeSet and prints the name of each Drink object.What is the result?

int[] myArray = new int[] {1, 2, 3, 4, 5};
List myList = myArray.asList();List myList = Arrays.asList(myArray);List myList = new ArrayList(myArray);List myList = Collections.fromArray(myArray);

32)Which statement is true?

public class Drink implements Comparable
{
public String name;
public int compareTo(Object o)
{
return 0;
}
}
and:
Drink one = new Drink();
Drink two = new Drink();
one.name= "Coffee";
two.name= "Tea";
TreeSet set = new TreeSet();
set.add(one);
set.add(two);
TeaCoffeeCoffee TeaCompilation failsThe code runs with no output.

33)Which statement is true?

public class TestSeven extends Thread {
private static int x;
public synchronized void doThings() {
int current = x;
current++;
x = current;
}
public void run() {
doThings();
}
}public class TestSeven extends Thread {
private static int x;
public synchronized void doThings() {
int current = x;
current++;
x = current;
}
public void run() {
doThings();
}
}public class TestSeven extends Thread {
private static int x;
public synchronized void doThings() {
int current = x;
current++;
x = current;
}
public void run() {
doThings();
}
}public class TestSeven extends Thread {
private static int x;
public synchronized void doThings() {
int current = x;
current++;
x = current;
}
public void run() {
doThings();
}
}
Compilation fails.An exception is thrown at runtime.Synchronizing the run() method would make the class thread-safeThe data in variable "x" are protected from concurrent access problems.Declaring the doThings() method as static would make the class thread-safe.

34)Which statement is true?

void waitForSignal() {
Object obj = new Object();
synchronized (Thread.currentThread()) {
obj.wait();
obj.notify();
}
}
This code may throw an InterruptedExceptionThis code may throw an IllegalStateException.This code may throw a TimeoutException after ten minutesThis code will not compile unless "obj.wait()" is replaced with "((Thread) obj).wait()".Reversing the order of obj.wait() and obj.notify() may cause this method to complete normally.

35)What can be a result?

public class TestOne implements Runnable
{
public static void main (String[] args) throws Exception
{
Thread t = new Thread(new TestOne());
t.start();
System.out.print("Started");
t.join();
System.out.print("Complete");
}
public void run()
{
for (int i = 0; i < 4; i++)
{
System.out.print(i);
}
}
}
Compilation fails.An exception is thrown at runtime.The code executes and prints "StartedComplete".The code executes and prints "StartedComplete0123".The code executes and prints Started0123Complete

36)What is the result?

Runnable r = new Runnable()
{
public void run()
{
System.out.print("Cat");
}
};
Thread t = new Thread(r)
{
public void run()
{
System.out.print("Dog");
}
};
t.start();
CatDogCompilation fails.The code runs with no output.An exception is thrown at runtime.

37)Assume that sleep(n) executes in exactly m milliseconds, and all other*

Compilation fails.Deadlock occurs.StartMain Start1 EndMain End1 Start2 End2StartMain Start1 Start2 Error End2 EndMain End1StartMain Start1 EndMain End1 Start2 Error End2

38)code executes in an insignificant amount of time. What is the output if*

/test/Chess.class/home/bob/Chess.class/test/games/Chess.class/home/bob/games/Chess.classinside jarfile /home/bob/downloads/Games.jar (with a correct manifest)

39)the main() method is run?*

put Poker.jar in directory /stuff/java, and set the CLASSPATH to include /stuff/javaput Poker.jar in directory /stuff/java, and set the CLASSPATH to include /stuff/java/*.jarPut Poker.jar in directory /stuff/java, and set the CLASSPATH to include /stuff/java/Poker.jarput Poker.jar in directory /stuff/java/games/cards, and set the CLASSPATH to include /stuff/java/*.jarput Poker.jar in directory /stuff/java/games/cards, and set the CLASSPATH to include /stuff/java/Poker.ja

40)What is the result?

public class Test
{
public static void main(String [] args)
{
int x = 5;
boolean b1 = true;
boolean b2 = false;
if ((x == 4) && !b2 )
System.out.print("1 ");
System.out.print("2 ");
if ((b2 = true) && b1 )
System.out.print("3 ");
}
}
231223123

41)What is the result?

Given the command line java Pass2 and:
public class Pass2
{
public void main(String [] args)
{
int x = 6;
Pass2 p = new Pass2();
p.doStuff(x);
System.out.print(" main x = " + x);
}
void doStuff(int x)
{
System.out.print(" doStuff x = " + x++);
}
}
Compilation failsAn exception is thrown at runtimedoStuff x = 6 main x = 6doStuff x = 6 main x = 7oStuff x = 7 main x = 7

42)What is the result?

os.writeObject(f); os.close();
} catch (Exception ex) { ex.printStackTrace(); }
} }

class Tree { }
Compilation failsAn exception is thrown at runtime.An instance of Forest is serializedAn instance of Forest and an instance of Tree are both serialized.

43)What is the result?

import java.io.*;
public class Forest implements Serializable
{
private Tree tree = new Tree();
public static void main(String [] args)
{
Forest f = new Forest();
try
{
FileOutputStream fs = new FileOutputStream("Forest.ser");
ObjectOutputStream os = new ObjectOutputStream(fs);
os.writeObject(f); os.close();
}
catch (Exception ex)
{ ex.printStackTrace(); }
}
}
class Tree { }
Compilation fails.An exception is thrown at runtime.An instance of Forest is serialized.An instance of Forest and an instance of Tree are both serialized.

44)When comparing java.io.BufferedWriter to java.io.FileWriter, whichcapability exists as a method in only one of the two?*

closing the streamflushing the streamwriting to the streammarking a location in the streamwriting a line separator to the stream

45)Which code fragment, inserted at line 15, will allow Foo objects to becorrectly serialized and deserialized?

public class Foo implements java.io.Serializable
{
private int x;
public int getX()
{ return x; }
publicFoo(int x)
{this.x=x; }
private void writeObject( ObjectOutputStream s)
throws IOException
{
// insert code here
}
}
s.writeInt(x);s.serialize(x);s.writeObject(x);s.defaultWriteObject();

46)What is the result?

Assuming that the serializeBanana() and the deserializeBanana() methods will
correctly use Java serialization and given:
import java.io.*;
class Food implements Serializable {int good = 3;}
class Fruit extends Food {int juice = 5;}
public class Banana extends Fruit {
int yellow = 4;
public static void main(String [] args) {
Banana b = new Banana(); Banana b2 = new Banana();
b.serializeBanana(b); // assume correct serialization
b2 = b.deserializeBanana(); // assume correct
System.out.println("restore "+b2.yellow+ b2.juice+b2.good);
} // more Banana methods go here 50. }
restore 400restore 403restore 453Compilation fails.An exception is thrown at runtime.

47)What is the result?

Assuming that the serializeBanana2() and the deserializeBanana2() methods
will correctly use Java serialization and given:
import java.io.*;
class Food
{
Food()
{
System.out.print("1");
}
}
class Fruit extends Food implements Serializable
{
Fruit()
{
System.out.print("2");
}
}
public class Banana2 extends Fruit
{
int size = 42;
public static void main(String [] args)
{
Banana2 b = new Banana2();
b.serializeBanana2(b); // assume correct serialization
b = b.deserializeBanana2(b); // assume correct
System.out.println(" restored " + b.size + " ");
}
// more Banana2 methods
}
Compilation fails.1 restored 4212 restored 42121 restored 421212 restored 42

48)Given:1. public class GC {2. private Object o;3. private void doSomethingElse(Object obj) { o = obj; }4. public void doSomething() {5. Object o = new Object();6. doSomethingElse(o);7. o = new Object();8. doSomethingElse(null);9. o = null;10. }11. }When th*

Line 5Line 6Line 7Line 8Line 9

49)Given:rbo = new ReallyBigObject(); // more code here rbo = null;14. /* insert code here */Which statement should be placed at line 14 to suggest that the virtual machine expend effort towardrecycling the memory used by the object rbo?*

System.gc();Runtime.gc();System.freeMemory();Runtime.getRuntime().growHeap();Runtime.getRuntime().freeMemory();

50)What is the result?

public class Test
{
public static void main(String [] args)
{
int x = 5;
boolean b1 = true;
boolean b2 = false;
if ((x == 4) && !b2 )
System.out.print("1 ");
System.out.print("2 ");
if ((b2 = true) && b1 )
System.out.print("3 ");
}
}
231223123

51)What is the result?

the command line java Pass2 and:
public class Pass2
{
public void main(String [] args)
{
int x = 6;
Pass2 p = new Pass2();
p.doStuff(x);
System.out.print(" main x = " + x);
}
void doStuff(int x)
{
System.out.print(" doStuff x = " + x++);
}
}
Compilation fails.An exception is thrown at runtime.doStuff x = 6 main x = 6doStuff x = 6 main x = 7doStuff x = 6 main x = 7doStuff x = 7 main x = 6

52)What is the result?

public class Pass
{
public static void main(String [] args)
{
int x = 5;
Pass p = new Pass();
p.doStuff(x);
System.out.print(" main x = " + x);
}
void doStuff(int x)
{
System.out.print(" doStuff x = " + x++);
}
}
Compilation fails.An exception is thrown at runtime.doStuff x = 6 main x = 6doStuff x = 5 main x = 5doStuff x = 5 main x = 6

53)What is the result?

public class ClassA
{
public int getValue()
{
Int value=0;
boolean setting = true;
String title=”Hello”;
if (value || (setting && title == “Hello”))
{ return 1; }
if (value == 1 & title.equals(”Hello”)) { return 2; }
}
}
And:
ClassA a = new ClassA();
a.getValue();
12Compilation fails.The code runs with no output.An exception is thrown at runtime.

54)What is the result?

Given:
interface A
{
public void aMethod();
}
interface B
{
public void bMethod();
}
interface C extends A,B
{
public void cMethod();
}
class D implements B
{
public void bMethod(){}
}
class E extends D implements C
{
public void aMethod(){}
public void bMethod(){}
public void cMethod(){}
}
What is the result?
Compilation fails because of an error in line 3.Compilation fails because of an error in line 7.Compilation fails because of an error in line 9.If you define D e = new E(), then e.bMethod() invokes the version of bMethod()defined in Line 5.If you define D e = (D)(new E()), then e.bMethod() invokes the version of bMethod()defined in Line 9.

55)Which statement is true?

public class CreditCard
{
private String cardID;
private Integer limit;
public String ownerName;
public void setCardInformation(String cardID,
String ownerName,
Integer limit)
{
this.cardID = cardID;
this.ownerName = ownerName;
this.limit = limit;
}
}
The class is fully encapsulated.The code demonstrates polymorphism.The ownerName variable breaks encapsulation.The cardID and limit variables break polymorphism.

56)What is the result of executing XMLMessage.main?

classes defined in two different files:
package packageA;
public class Message
{
String getText()
{ return "text"; }
}
and:
package packageB;
public class XMLMessage extends packageA.Message
{
String getText()
{
return "text";
}
public static void main(String[] args)
{
System.out.println(new XMLMessage().getText());
}
}
textAn exception is thrown at runtime.Compilation fails because of an error in line 2 of XMLMessage.Compilation fails because of an error in line 3 of XMLMessage.

57)What is the result?

public class Foo
{
public int a;
public Foo()
{
a = 3;
}
public void addFive()
{
a += 5;
}
}
and:
public class Bar extends Foo
{
public int a;
public Bar() { a = 8; }
public void addFive()
{
this.a += 5;
}
} invoked with:
Foo foo = new Bar();
foo.addFive();
System.out.println("Value: " + foo.a);
Value: 3Value: 8Value: 13Compilation fails.

58)What is the result?

String test = "This is a test";
String[] tokens = test.split("s");
System.out.println(tokens.length);
014Compilation fails.

59)What is the result?

System.out.format("Pi is approximately %d.", Math.PI);
Compilation failsPi is approximately 3.Pi is approximately 3.141593.An exception is thrown at runtime.

60)Which of the following statements are true?*

Methods cannot be overriden to be more privatestatic methods cannot be overloadedprivate methods cannot be overloadedAn overloaded method cannot throw exceptions not checked in the base class
Should be Empty: