Question 1)
Which of the following lines will compile without warning or error.
1) float f=1.3;
2) char c="a";
3) byte b=257;
4) boolean b=null;
5) int i=10;
Question 2)
What will happen if you try to compile and run the following code
public class MyClass {
public static void main(String arguments[]) {
amethod(arguments);
}
public void amethod(String[] arguments) {
System.out.println(arguments);
System.out.println(arguments[1]);
}
}1) error Can't make static reference to void amethod.
2) error method
main not correct
3) error array must include parameter
4) amethod must
be declared with String
Question 3)
Which of the following will compile without error
1)
import java.awt.*;
package Mypackage;
class Myclass {}2)
package MyPackage;
import java.awt.*;
class MyClass{}3)
/*This is a comment */
package MyPackage;
import java.awt.*;
class MyClass{}Question 4)
A byte can be of what size
1) -128 to 127
2) (-2 power 8 )-1 to 2 power 8
3) -255 to 256
4)depends on the particular implementation of the Java Virtual machine
Question 5)
What will be printed out if this code is run with the following command line?
java myprog good morning
public class myprog{
public static void main(String argv[])
{
System.out.println(argv[2]);
}
}
1) myprog 2) good
3) morning
4) Exception raised:
"java.lang.ArrayIndexOutOfBoundsException: 2"
Question 6)
Which of the following are keywords or reserved words in Java?
1) if
2) then
3) goto
4) while
5) case
Question 7)
Which of the following are legal identifiers
1) 2variable
2) variable2
3) _whatavariable
4) _3_
5)
$anothervar
6) #myvar
Question 8)
What will happen when you compile and run the following code?
public class MyClass{
static int i;
public static void main(String argv[]){
System.out.println(i);
}
}1) Error Variable i may not have been initialized
2) null
3) 1
4)
0
Question 9)
What will happen if you try to compile and run the following code?
public class Q {
public static void main(String argv[]){
int anar[]=new int[]{1,2,3};
System.out.println(anar[1]);
}
}1) 1
2) Error anar is referenced before it is initialized
3) 2
4)
Error: size of array must be defined
Question 10)
What will happen if you try to compile and run the following code?
public class Q {
public static void main(String argv[]){
int anar[]=new int[5];
System.out.println(anar[0]);
}
}1) Error: anar is referenced before it is initialized
2) null
3) 0
4) 5
Question 11)
What will be the result of attempting to compile and run the following
code?
abstract class MineBase {
abstract void amethod();
static int i;
}
public class Mine extends MineBase {
public static void main(String argv[]){
int[] ar=new int[5];
for(i=0;i < ar.length;i++)
System.out.println(ar[i]);
}
}1) a sequence of 5 0's will be printed
2) Error: ar is used before it is
initialized
3) Error Mine must be declared abstract
4) IndexOutOfBoundes
Error
Question 12)
What will be printed out if you attempt to compile and run the following code
?
int i=1;
switch (i) {
case 0:
System.out.println("zero");
break;
case 1:
System.out.println("one");
case 2:
System.out.println("two");
default:
System.out.println("default");
}1) one
2) one, default
3) one, two, default
4) default
Question 13)
What will be printed out if you attempt to compile and run the following
code?
int i=9;
switch (i) {
default:
System.out.println("default");
case 0:
System.out.println("zero");
break;
case 1:
System.out.println("one");
case 2:
System.out.println("two");
}1) default
2) default, zero
3) error default clause not defined
4) no output displayed
Question 14)
Which of the following lines of code will compile without error
1)
int i=0;
if(i) {
System.out.println("Hello");
}2)
boolean b=true;
boolean b2=true;
if(b==b2) {
System.out.println("So true");
}3)
int i=1;
int j=2;
if(i==1|| j==2)
System.out.println("OK");4)
int i=1;
int j=2;
if(i==1 &| j==2)
System.out.println("OK");Question 15)
What will be output if you try to compile and run the following code, but
there is
no file called Hello.txt in the current directory?.
import java.io.*;
public class Mine {
public static void main(String argv[]){
Mine m=new Mine();
System.out.println(m.amethod());
}
public int amethod() {
try {
FileInputStream dis=new FileInputStream("Hello.txt");
}catch (FileNotFoundException fne) {
System.out.println("No such file found");
return -1;
}catch(IOException ioe) {
} finally{
System.out.println("Doing finally");
}
return 0;
}
}
1) No such file found
2 No such file found ,-1
3) No such file found,
Doing finally, -1
4) 0
Question 16)
Which of the following statements are true?
1) Methods cannot be overriden to be more private
2) static methods cannot
be overloaded
3) private methods cannot be overloaded
4) An overloaded
method cannot throw exceptions not checked in the base class
16
Question 17)
What will happen if you attempt to compile and run the following code?
class Base {}
class Sub extends Base {}
class Sub2 extends Base {}
public class CEx{
public static void main(String argv[]){
Base b=new Base();
Sub s=(Sub) b;
}
}
1) Compile and run without error
2) Compile time Exception
3) Runtime
Exception
Question 18)
Which of the following statements are true?
1) System.out.println( -1 >>> 2);will output a result larger than
10
2) System.out.println( -1 >>> 2); will output a positive number
3) System.out.println( 2 >> 1); will output the number 1
4)
System.out.println( 1 <<< 2); will output the number 4
Question 19)
What will happen when you attempt to compile and run the following code?
public class Tux extends Thread{
static String sName = "vandeleur";
public static void main(String argv[]){
Tux t = new Tux();
t.piggy(sName);
System.out.println(sName);
}
public void piggy(String sName){
sName = sName + " wiggy";
start();
}
public void run(){
for(int i=0;i < 4; i++){
sName = sName + " " + i;
}
}
}
1) Compile time error2) Compilation and output of "vandeleur
wiggy"
3) Compilation and output of "vandeleur wiggy 0 1 2 3"
4)
Compilation and output of either "vandeleur", "vandeleur 0", "vandeleur 0 1"
"vandaleur 0 1 2" or "vandaleur 0 1 2 3"
Answer to Question
19
Question 20)
What will be displayed when you attempt to compile and run the following
code
//Code start
import java.awt.*;
public class Butt extends Frame{
public static void main(String argv[]){
Butt MyBut=new Butt();
}
Butt(){
Button HelloBut=new Button("Hello");
Button ByeBut=new Button("Bye");
add(HelloBut);
add(ByeBut);
setSize(300,300);
setVisible(true);
}
}
//Code end
1) Two buttons side by side occupying all of the frame, Hello on the left and
Bye on
the right
2) One button occupying the entire frame saying Hello
3) One button occupying the entire frame saying Bye
4) Two buttons at
the top of the frame one saying Hello the other saying Bye
Question 21)
What will be output by the following code?
public class MyFor{
public static void main(String argv[]){
int i;
int j;
outer:
for (i=1;i <3;i++)
inner:
for(j=1; j<3; j++) {
if (j==2)
continue outer;
System.out.println("Value for i=" + i + " Value for j=" +j);
}
}
}
1) Value for i=1 Value for j=1
2) Value for i=2 Value for j=1
3)
Value for i=2 Value for j=2
4) Value for i=3 Value for j=1
Which statement is true of the following code?
public class Agg{
public static void main(String argv[]){
Agg a = new Agg();
a.go();
}
public void go(){
DSRoss ds1 = new DSRoss("one");
ds1.start();
}
}
class DSRoss extends Thread{
private String sTname="";
DSRoss(String s){
sTname = s;
}
public void run(){
notwait();
System.out.println("finished");
}
public void notwait(){
while(true){
try{
System.out.println("waiting");
wait();
}catch(InterruptedException ie){}
System.out.println(sTname);
notifyAll();
}
}
}
1) It will cause a compile time error
2) Compilation and output of
"waiting"
3) Compilation and output of "waiting" followed by "finished"
4)
Runtime error, an exception will be thrown
Question 23)
Which of the following methods can be legally inserted in place of the
comment //Method Here ?
class Base{
public void amethod(int i) { }
}
public class Scope extends Base{
public static void main(String argv[]){
}
//Method Here
}1) void amethod(int i) throws Exception {}
2) void amethod(long i)throws
Exception {}
3) void amethod(long i){}
4) public void amethod(int i)
throws Exception {}
Question 24)
Which of the following will output -4.0
1) System.out.println(Math.floor(-4.7));
2)
System.out.println(Math.round(-4.7));
3)
System.out.println(Math.ceil(-4.7));
4) System.out.println(Math.min(-4.7));
Question 25)
What will happen if you attempt to compile and run the following code?
Integer ten=new Integer(10); Long nine=new Long (9); System.out.println(ten + nine); int i=1; System.out.println(i + ten);
1) 19 followed by 20
2) 19 followed by 11
3) Compile time error
4) 10 followed by 1
Question 26)
If you run the code below, what gets printed out?
String s=new String("Bicycle");
int iBegin=1;
char iEnd=3;
System.out.println(s.substring(iBegin,iEnd));1) Bic
2) ic
3) icy
4) error: no method matching
substring(int,char)
Question 27)
If you wanted to find out where the position of the letter v (ie return 2) in
the string s
containing "Java", which of the following could you use?
1) mid(2,s);
2) charAt(2);
3) s.indexOf('v');
4) indexOf(s,'v');
Question 28)
Given the following declarations
String s1=new String("Hello")
String s2=new String("there");
String s3=new String();Which of the following are legal operations?
1) s3=s1 + s2;
2) s3=s1-s2;
3) s3=s1 & s2;
4) s3=s1
&& s2
Question 29)
What is the result of the following operation?
System.out.println(4 | 3);
1) 6
2) 0
3) 1
4) 7
Question 30)
public class MyClass1 {
public static void main(String argv[]){ }
/*Modifier at XX */ class MyInner {}
}What modifiers would be legal at XX in the above code?
1) public
2) private
3) static
4) friend
Question 31)
What will happen when you attempt to compile and run the following
code?
public class Holt extends Thread{
private String sThreadName;
public static void main(String argv[]){
Holt h = new Holt();
h.go();
}
Holt(){}
Holt(String s){
sThreadName = s;
}
public String getThreadName(){
return sThreadName;
}
public void go(){
Holt first = new Holt("first");
first.start();
Holt second = new Holt("second");
second.start();
}
public void start(){
for(int i = 0; i < 2; i ++){
System.out.println(getThreadName() +i);
try{
Thread.sleep(100);
} catch(InterruptedException e){System.out.println(e.getMessage());}
}
}
}
1) Compile time error
2) Output of first0, second0, first0, second1
3)
Output of first0, first1, second0, second1
4) Runtime error
Question 32)
An Applet has its Layout Manager set to the default of FlowLayout. What code
would be correct to change to another Layout Manager.
1) setLayoutManager(new GridLayout());
2) setLayout(new GridLayout(2,2));
3) setGridLayout(2,2);
4) setBorderLayout();
Question 33)
What will happen when you attempt to compile and run the following code?.
class Background implements Runnable{
int i=0;
public int run(){
while(true){
i++;
System.out.println("i="+i);
} //End while
return 1;
}//End run
}//End class
1) It will compile and the run method will print out the increasing value of
i.
2) It will compile and calling start will print out the increasing value
of i.
3) The code will cause an error at compile time.
4) Compilation
will cause an error because while cannot take a parameter of true.
Which of the following statements about this code are true?
public class Morecombe{
public static void main(String argv[]){
Morecombe m = new Morecombe();
m.go(new Turing(){});
}
public void go(Turing t){
t.start();
}
}
class Turing extends Thread{
public void run(){
for(int i =0; i < 2; i++){
System.out.println(i);
}
}
}
1) Compilation error due to malformed parameter to go method
2)
Compilation error, class Turing has no start method
3) Compilation and output
of 0 followed by 1
4) Compilation but runtime error
Question 35)
What will be the result when you attempt to compile and run the following
code?.
public class Conv{
public static void main(String argv[]){
Conv c=new Conv();
String s=new String("ello");
c.amethod(s);
}
public void amethod(String s){
char c='H';
c+=s;
System.out.println(c);
}
}
1) Compilation and output the string "Hello"
2) Compilation and output
the string "ello"
3) Compilation and output the string elloH
4) Compile
time error
Question 36)
Given the following code, what test would you need to put in place of the
comment line?
//place test here
to result in an output of the string
Equal
public class EqTest{
public static void main(String argv[]){
EqTest e=new EqTest();
}
EqTest(){
String s="Java";
String s2="java";
//place test here {
System.out.println("Equal");
}else
{
System.out.println("Not equal");
}
}
}1) if(s==s2)
2) if(s.equals(s2)
3) if(s.equalsIgnoreCase(s2))
4)if(s.noCaseMatch(s2))
Question 37)
Given the following code
import java.awt.*;
public class SetF extends Frame{
public static void main(String argv[]){
SetF s=new SetF();
s.setSize(300,200);
s.setVisible(true);
}
}How could you set the frame surface color to pink
1)s.setBackground(Color.pink);
2)s.setColor(PINK);
3)s.Background(pink);
4)s.color=Color.pink
Question 38)
How can you change the current working directory using an instance of the
File class called FileName?
1) FileName.chdir("DirName")
2)
FileName.cd("DirName")
3) FileName.cwd("DirName")
4) The File class does
not support directly changing the current directory.
Question 39)
If you create a TextField with a constructor to set it to occupy 5
columns, what difference will it make if you use it with a proportional font (ie
Times Roman) or a fixed pitch typewriter style font (Courier).
1)With a fixed font you will see 5 characters, with a proportional it
will depend on the width of the characters
2)With a fixed font you will see
5 characters,with a proportional it will cause the field to expand to fit
the text
3)The columns setting does not affect the number of characters
displayed
4)Both will show exactly 5 characters
Question 40)
Given the following code how could you invoke the Base constructor that
will print out the string "base constructor";
class Base{
Base(int i){
System.out.println("base constructor");
}
Base(){
}
}
public class Sup extends Base{
public static void main(String argv[]){
Sup s= new Sup();
//One
}
Sup()
{
//Two
}
public void derived()
{
//Three
}
}
1) On the line After //One put Base(10);
2) On the line After //One put
super(10);
3) On the line After //Two put super(10);
4) On the line
After //Three put super(10);
Question 41)
Given the following code what will be output?
public class Pass{
static int j=20;
public static void main(String argv[]){
int i=10;
Pass p = new Pass();
p.amethod(i);
System.out.println(i);
System.out.println(j);
}
public void amethod(int x){
x=x*2;
j=j*2;
}
}
1) Error: amethod parameter does not match variable
2) 20 and 40
3)
10 and 40
4) 10, and 20
Question 42)
What code placed after the comment //For loop would result in the
population of every element of the array ia[] with a value from variable i.?
public class Lin{
public static void main(String argv[]){
Lin l = new Lin();
l.amethod();
}
public void amethod(){
int ia[] = new int[4];
//Start For loop
{
ia[i]=i;
System.out.println(ia[i]);
}
}
}
1) for(int i=0; i < ia.length() -1; i++)
2) for (int i=0; i<
ia.length(); i++)
3) for(int i=1; i < 4; i++)
4) for(int i=0; i<
ia.length;i++)
Question 43)
What will be the result when you try to compile and run the following
code?
private class Base{
Base(){
int i = 100;
System.out.println(i);
}
}
public class Pri extends Base{
static int i = 200;
public static void main(String argv[]){
Pri p = new Pri();
System.out.println(i);
}
}
1) Error at compile time
2) 200
3) 100 followed by 200
4) 100
Question 44)
What will the following code print out?
public class Oct{
public static void main(String argv[]){
Oct o = new Oct();
o.amethod();
}
public void amethod(){
int oi= 012;
System.out.println(oi);
}
}
1)12
2)012
3)10
4)10.0
Question 45
What will happen when you try compiling and running this code?
public class Ref{
public static void main(String argv[]){
Ref r = new Ref();
r.amethod(r);
}
public void amethod(Ref r){
int i=99;
multi(r);
System.out.println(i);
}
public void multi(Ref r){
r.i = r.i*2;
}
}
1) Error at compile time
2) An output of 99
3) An output of 198
4) An error at runtime
Question 46)
You need to create a class that will store unique object elements. You do not
need to sort these elements but they must be unique.
What interface might be most suitable to meet this need?
1)Set
2)List
3)Map
4)Vector
Question 47)
Which of the following will successfully create an instance of the Vector
class and add an element?
1) Vector v=new Vector(99);
v[1]=99;
2) Vector v=new Vector();
v.addElement(99);
3) Vector v=new Vector();
v.add(99);
4 Vector v=new Vector(100);
v.addElement("99");
Question 48)
You have created a simple Frame and overridden the paint method as follows
public void paint(Graphics g){
g.drawString("Dolly",50,10);
}
What will be the result when you attempt to compile and run the program?
1) The string "Dolly" will be displayed at the centre of the frame
2) An
error at compilation complaining at the signature of the paint method
3) The
lower part of the word Dolly will be seen at the top of the frame, with the top
hidden.
4) The string "Dolly" will be shown at the bottom of the frame.
Question 49)
What will be the result when you attempt to compile this program?
public class Rand{
public static void main(String argv[]){
int iRand;
iRand = Math.random();
System.out.println(iRand);
}
}
1) Compile time error referring to a cast problem
2) A random number
between 1 and 10
3) A random number between 0 and 1
4) A compile time
error about random being an unrecognised method
Question 50)
Given the following code
import java.io.*;
public class Th{
public static void main(String argv[]){
Th t = new Th();
t.amethod();
}
public void amethod(){
try{
ioCall();
}catch(IOException ioe){}
}
}
What code would be most likely for the body of the ioCall method
1) public void ioCall ()throws IOException{
DataInputStream din = new DataInputStream(System.in);
din.readChar();
}
2) public void ioCall ()throw IOException{
DataInputStream din = new DataInputStream(System.in);
din.readChar();
}
3) public void ioCall (){
DataInputStream din = new DataInputStream(System.in);
din.readChar();
}
4) public void ioCall throws IOException(){
DataInputStream din = new DataInputStream(System.in);
din.readChar();
}Question 51)
What will happen when you compile and run the following code?
public class Scope{
private int i;
public static void main(String argv[]){
Scope s = new Scope();
s.amethod();
}//End of main
public static void amethod(){
System.out.println(i);
}//end of amethod
}//End of class
1) A value of 0 will be printed out
2) Nothing will be printed out
3)
A compile time error
4) A compile time error complaining of the scope of the
variable i
Question 52)
You want to lay out a set of buttons horizontally but with more space
between the first button and the rest. You are going to use the GridBagLayout manager to control the way the buttons are set out.
How will you modify the way the GridBagLayout acts in order to change the
spacing around the first button?
1) Create an instance of the GridBagConstraints class, call the weightx()
method and then pass the GridBagConstraints instance with the component to the
setConstraints method of the GridBagLayout class.
2) Create an instance of
the GridBagConstraints class, set the weightx field and then pass the
GridBagConstraints instance with the component to the setConstraints method of
the GridBagLayout class.
3) Create an instance of the GridBagLayout class,
set the weightx field and then call the setConstraints method of the
GridBagLayoutClass with the component as a parameter.
4) Create an instance
of the GridBagLayout class, call the setWeightx() method and then pass the
GridBagConstraints instance with the component to the setConstraints method of
the GridBagLayout class.
Question 53)
Which of the following can you perform using the File class?
1) Change the current directory
2) Return the name of the parent
directory
3) Delete a file
4) Find if a file contains text or binary
information
Which statement is true of the following code?
public class Rpcraven{
public static void main(String argv[]){
Pmcraven pm1 = new Pmcraven("One");
pm1.run();
Pmcraven pm2 = new Pmcraven("Two");
pm2.run();
}
}
class Pmcraven extends Thread{
private String sTname="";
Pmcraven(String s){
sTname = s;
}
public void run(){
for(int i =0; i < 2 ; i++){
try{
sleep(1000);
}catch(InterruptedException e){}
yield();
System.out.println(sTname);
}
}
}
1) Compile time error, class Rpcraven does not import java.lang.Thread
2)
Output of One One Two Two
3) Output of One Two One Two
4) Compilation but
no output at runtime
Question 55)
You are concerned that your program may attempt to use more memory than is
available. To avoid this situation you want to ensure that the Java Virtual
Machine will run its garbage collection just before you start a complex routine.
What can you do to be certain that garbage collection will run when you want .
1) You cannot be certain when garbage collection will run
2) Use the
Runtime.gc() method to force garbage collection
3) Ensure that all the
variables you require to be garbage collected are set to null
4) Use the
System.gc() method to force garbage collection
Question 56)
You are using the GridBagLayout manager to place a series of buttons on a
Frame. You want to make the size of one of the buttons bigger than the text it
contains. Which of the following will allow you to do that?
1) The GridBagLayout manager does not allow you to do this
2) The setFill
method of the GridBagLayout class
3) The setFill method of the
GridBagConstraints class
4) The fill field of the GridBagConstraints class
Question 57)
Which of the following most closely describes a bitset collection?
1) A class that contains groups of unique sequences of bits
2) A method
for flipping individual bits in instance of a primitive type
3) An array of
boolean primitives that indicate zeros or ones
4) A collection for storing
bits as on-off information, like a vector of bits
Question 58)
You have these files in the same directory. What will happen when you
attempt to compile and run Class1.java if you have not already compiled
Base.java
//Base.java
package Base;
class Base{
protected void amethod(){
System.out.println("amethod");
}//End of amethod
}//End of class base
package Class1;
//Class1.java
public class Class1 extends Base{
public static void main(String argv[]){
Base b = new Base();
b.amethod();
}//End of main
}//End of Class1
1) Compile Error: Methods in Base not found
2) Compile Error: Unable to
access protected method in base class
3) Compilation followed by the output
"amethod"
4)Compile error: Superclass Class1.Base of class Class1.Class1 not
found
Question 59)
What will happen when you attempt to compile and run the following code
class Base{
private void amethod(int iBase){
System.out.println("Base.amethod");
}
}
class Over extends Base{
public static void main(String argv[]){
Over o = new Over();
int iBase=0;
o.amethod(iBase);
}
public void amethod(int iOver){
System.out.println("Over.amethod");
}
}
1) Compile time error complaining that Base.amethod is private
2) Runtime
error complaining that Base.amethod is private
3) Output of
"Base.amethod"
4) Output of "Over.amethod"
Question 60)
You are creating an applet with a Frame that contains buttons. You are using
the GridBagLayout manager and you have added Four buttons. At the moment the
buttons appear in the centre of the frame from left to right. You want them to
appear one on top of the other going down the screen. What is the most
appropriate way to do this.
1) Set the gridy value of the GridBagConstraints class to a value increasing
from 1 to 4
2) set the fill value of the GridBagConstraints class to
VERTICAL
3) Set the ipady value of the GridBagConstraints class to a value
increasing from 0 to 4
4) Set the fill value of the GridBagLayouts class to
GridBag.VERTICAL
Answers
Answer 1)
Back to
question 1)
Objective 4.5)
5) int i=10;
explanation:
1) float f=1.3;
Will not compile because the default
type of a number with a floating point component is a double. This would compile
with a cast as in
float f=(float) 1.3
2) char c="a";
Will not compile because a char (16 bit unsigned integer) must be defined
with single quotes. This would compile if it were in the form
char c='a';
3) byte b=257;
Will not compile because a byte is eight bits. Take of one bit for the sign
component you can define numbers between
-128 to +127
4) a boolean value can either be true or false, null is not allowed
Answer 2)
Objective 4.1
1) Can't make static reference to void amethod.
Because main is defined as static you need to create an instance of the class
in order to call any non-static methods. Thus a typical way to do this would be.
MyClass m=new MyClass();
m.amethod();
Answer 2 is an attempt to confuse because the convention is for a main method
to be in the form
String argv[]
That argv is just a convention and any acceptable identifier for a string
array can be used. Answers 3 and 4 are just nonsense.
Answer 3)
back to
Question 3)
Objective 4.1)
2 and 3 will compile without error.
1 will not compile because any package declaration must come before any other
code. Comments may appear anywhere
Answer 4)
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question 4)
Objective 4.5)
1) A byte is a signed 8 bit integer.
Answer 5)
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question 5)
Objective 4.2)
4) Exception raised: "java.lang.ArrayIndexOutOfBoundsException: 2"
Unlike C/C++ java does not start the parameter count with the program name.
It does however start from zero. So in this case zero starts with good, morning
would be 1 and there is no parameter 2 so an exception is raised.
Answer 6)
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question 6)
Objective 4.3)
1) if
3) goto
4) while
5) case
then is not a Java keyword, though if you are from a VB background you
might think it was. Goto is a reserved word in Java.
Answer 7)
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Question 7)
Objective 4.1)
2) variable2
3) _whatavariable
4) _3_
5) $anothervar
An identifier can begin with a letter (most common) or a dollar sign($) or an
underscore(_). An identifier cannot start with anything else such as a number, a
hash, # or a dash -. An identifier cannot have a dash in its body, but it may
have an underscore _. Choice 4) _3_ looks strange but it is an acceptable, if
unwise form for an identifier.
Answer 8)
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Question 8)
Objective 4.4)
4) 0
Class level variables are always initialised to default values. In the case
of an int this will be 0. Method level variables are not given default values
and if you attempt to use one before it has been initialised it will cause the
Error Variable i may not have been initialized
type of error.
Answer 9)
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Question 9)
Objective 4.4)
3 ) 2
No error will be triggered.
Like in C/C++, arrays are always referenced from 0. Java allows an array to
be populated at creation time. The size of array is taken from the number of
initializers. If you put a size within any of the square brackets you will get
an error.
Answer 10)
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question 10)
Objective 4.4)
3) 0
Arrays are always initialised when they are created. As this is an array of
ints it will be initalised with zeros.
Answer 11)
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Question 11)
Objective 1.2
3) Error Mine must be declared abstract
A class that contains an abstract method must itself be declared as abstract.
It may however contain non abstract methods. Any class derived from an abstract
class must either define all of the abstract methods or be declared abstract
itself.
Answer 12)
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Question 12)
Objective 2.1)
3) one, two, default
Code will continue to fall through a case statement until it encounters a
break.
Answer 13)
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Question 13)
Objective 4.1)
2) default, zero
Although it is normally placed last the default statement does not have to be
the last item as you fall through the case block. Because there is no case label
found matching the expression the default label is executed and the code
continues to fall through until it encounters a break.
Answer 14)
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Question 14)
Objective 5.1
2,3
Example 1 will not compile because if must always test a boolean. This can
catch out C/C++ programmers who expect the test to be for either 0 or not 0.
Answer 15)
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Question 15)
Objective 11.5)
3) No such file found, doing finally, -1
The no such file found message is to be expected, however you can get caught
out if you are not aware that the finally clause is almost always executed, even
if there is a return statement.
Answer 16)
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Question 16)
Objective 6.2)
1) Methods cannot be overriden to be more private
Static methods cannot be overriden but they can be overloaded. If you have
doubts about that statement, please follow and read carefully the link given to
the Sun tutorial below. There is no logic or reason why private methods should
not be overloaded. Option 4 is a jumbled up version of the limitations of
exceptions for overriden methods
Answer 17)
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Question 17)
Objective 6.2)
3) Runtime Exception
Without the cast to sub you would get a compile time error. The cast tells
the compiler that you really mean to do this and the actual type of b does not
get resolved until runtime. Casting down the object hierarchy is a problem, as
the compiler cannot be sure what has been implemented in descendent classes.
Casting up is not a problem because sub classes will have the features of the
base classes. This can feel counter intuitive if you are aware that with
primitives casting is allowed for widening operations (ie byte to int).
Answer 18)
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question 18)
Objective 5.1)
1) System.out.println( -1 >>> 2);will output a result larger than
10
2) System.out.println( -1 >>> 2); will output a positive number
3) System.out.println( 2 >> 1); will output the number 1
You can test this with the following class
public class shift{
static int i=2;
public static void main(String argv[]){
System.out.println( -1 >>> 2);
System.out.println( -1 >>> 2);
System.out.println( 2 >> 1);
}
}Java does not have a <<< operator. The operation 1 << 2 would
output 4
Because of the way twos complement number representation works the unsigned
right shift operation means a small shift in a negative number can return a very
large value so the output of option 1 will be much larger than 10.
The unsigned right shift places no significance on the leading bit that
indicates the sign. For this shift the value 1 of the bit sign is replaced with
a zero turning the result into a positive number for option 2.
Answer 19)
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Question 19)
Objective 7.1)
4) Compilation and output of either "vandaleur", "vandaleur 0", "vandaleur 0
1" "vandaleur 0 1 2" or "vandaleur 0 1 2 3"
If that seems a vauge answer it is because you cannot be certain of the
system that the underlying OS uses for allocating cycles for a Thread. The
chances are that once the thread has been spun off in the call to start in the
method piggy the main method will run to completion and the value of sName will
still be vandeluer before the Thread modifies it. You cannot be certain of this
though.
Answer 20)
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Question 20)
Objective 8.1)
3) One button occupying the entire frame saying Bye
The default layout manager for a Frame is a border layout. If directions are
not given (ie North, South, East or West), any button will simply go in the
centre and occupy all the space. An additional button will simply be placed over
the previous button. What you would probably want in a real example is to set up
a flow layout as in
setLayout(new FlowLayout());
Which would allow the buttons to both appear side by side, given the
appropriate font and size.
Applets and panels have a default FlowLayout
manager
Answer 21)
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Question 21)
Objective 2.2)
1,2
Value for i=1 Value for j=1
Value for i=2 Value for j=1
The statement continue outer causes the code to jump to the label outer and
the for loop increments to the next number.
Answer 22)
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22)
Objective 7.3)
4) Runtime error, an exception will be thrown
A call to wait/notify must be within synchronized code. With JDK1.2
this code throws the error message
java.lang.IllegalMonitorStateException: current thread not owner at java.lang.Object.wait(Native Method) at java.lang.Object.wait(Object.java:424) at DSRoss.notwait(Compiled Code) at DSRoss.run(Agg.java:21)
Answer 23)
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Question 23)
Objective 2.3)
2,3
Options 1, & 4 will not compile as they attempt to throw Exceptions not
declared in the base class. Because options 2 and 3 take a parameter of type
long they represent overloading not overriding and there is no such limitations
on overloaded methods.
Answer 24)
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Question 24)
Objective 9.1)
3) System.out.println(Math.ceil(-4.7));
Options 1 and 2 will produce -5 and option 4 will not compile because the min
method requires 2 parameters.
Answer 25)
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Question 25
Objective 4.5)
3) Compile time error
The wrapper classes cannot be used like primitives.
Depending on your compiler you will get an error that says someting like
"Error: Can't convert java lang Integer". Wrapper classes have similar names to
primitives but all start with upper case letters.
Thus in this case we have int as a primitive and Integer as a wrapper. The
objectives do not specifically mention the wrapper classes but don't be
surprised if they come up.
Answer 26)
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Question 26)
Objective 4.5)
2) ic
This is a bit of a catch question. Anyone with a C/C++ background would
figure out that addressing in strings starts with 0 so that 1 corresponds to i
in the string Bicycle. The catch is that the second parameter returns the
endcharacter minus 1. In this case it means instead of the "icy" being returned
as intuition would expect it is only "ic".
Answer 27)
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Question 27)
Objective 9.2)
3) s.indexOf('v');
charAt returns the letter at the position rather than searching for a letter
and returning the position, MID is just to confuse the Basic Programmers,
indexOf(s,'v'); is how some future VB/J++ nightmare hybrid, might perform such a
calculation.
Answer 28)
Objective 5.1)
Back to Question
28
1) s3=s1 + s2;
Java does not allow operator overloading as in C++, but for the sake of
convenience the + operator is overridden for strings.
Answer 29)
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Question 29)
Objective 5.3)
4) 7
The | is known as the Or operator, you could think of it as the either/or
operator. Turning the numbers into binary gives
4=100
3=011
For each position, if either number contains a 1 the result will contain a
result in that position. As every position contains a 1 the result will be
111
Which is decimal 7.
Answer 30)
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Question 30
Objective 4.1)
1,2,3
public, private, static are all legal access modifiers for this inner class.
Answer 31)
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Question 31
Objective 7.1
3) Output of first0, first1, second0, second1
Note that this code overrides and calls the start method. If you wished to
get the output mixed you would need to override the run method but call the
start method.
Answer 32)
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Question 32)
Objective 8.1)
2) setLayout(new GridLayout(2,2));
Changing the layout manager is the same for an Applet or an application.
Answer 1 is wrong though it might have been a reasonable name for the designers
to choose. Answers 3 and 4 are incorrect because changing the layout manager
always requires an instance of one of the Layout Managers and these are bogus
methods.
Instead of creating the anonymous instance of the Layout manager as in option
2 you can also create a named instance and pass that as a parameter. This is
often what automatic code generators such as Borland/Inprise JBuilder do.
Answer 33)
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Question 33)
Objective 7.1)
3) The code will cause an error at compile time
The error is caused because run should have a void not an int return type.
Any class that is implements an interface must create a method to match all
of the methods in the interface. The Runnable interface has one method called
run that has a void return type.The sun compiler gives the error
Method redefined with different return type: int run() was defined as void
run();
Answer 34)
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Question 34)
Objective 7.1)
3) Compilation and output of 0
followed by 1
The creation of an anonymous class as a parameter to go is fairly strange as
you would expect it to override a method in its parent class (Turing). You don't
have to though. The fact that class Turing extends Thread means the anonymous
instance that is passed to go has a start method which then calls the run
method.
Answer 35)
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Question 35
Objective 5.1)
4) Compile time error
The only operator overloading offered by java is the + sign for the String
class. A char is a 16 bit integer and cannot be concatenated to a string with
the + operator.
Answer 36)
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Question 36
Objective 5.2)
3) if(s.equalsIgnoreCase(s2))
String comparison is case sensitive so using the equals string method will
not return a match. Using the==operator just compares where memory address of
the references and noCaseMatch was just something I made up to give me a fourth
slightly plausible option.
Answer 37)
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Question 37
Objective 8.1)
1) s.setBackground(Color.pink);
For speakers of the more British spelt English note that there is no letter u
in Color. Also the constants for colors are in lower case.
Answer 38)
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Question 38)
Objective 11.1)
4) The File class does not support directly changing the current directory.
This seems rather surprising to me, as changing the current directory is a
very common requirement. You may be able to get around this limitation by
creating a new instance of the File class passing the new directory to the
constructor as the path name.
Answer 39)
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Question 39)
Objective 8.1)
1)With a fixed font you will see 5 characters, with a proportional it
will depend on the width of the characters
With a proportional font the letter w will occupy more space than the letter
i. So if you have all wide characters you may have to scroll to the right to see
the entire text of a TextField.
Answer 40)
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Question 40)
Objective 6.2
3) On the line After //Two put super(10);
Constructors can only be invoked from within constructors.
Answer 41)
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Question 41)
Objective 5.4)
3) 10 and 40
when a parameter is passed to a method the method receives a copy of the
value. The method can modify its value without affecting the original copy. Thus
in this example when the value is printed out the method has not changed the
value.
Answer 42)
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Question 42
Objective 1.1
4) for(int i=0; i< ia.length;i++)
Although you could control the looping with a literal number as with the
number 4 used in option 3, it is better practice to use the length property of
an array. This provides against bugs that might result if the size of the array
changes. This question also checks that you know that arrays starts from zero
and not One as option 3 starts from one. Remember that array length is a field
and not a function like the String length() method.
Answer 43)
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Question 43)
Objective 1.2
1) Error at compile time
This is a slightly sneaky one as it looks like a question about constructors,
but it is attempting to test knowledge of the use of the private modifier. A top
level class cannot be defined as private. If you didn't notice the modifier
private, remember in the exam to be real careful to read every part of the
question.
Answer 44)
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Question 44
Objective 4.5)
3)10
The name of the class might give you a clue with this question, Oct for
Octal. Prefixing a number with a zero indicates that it is in Octal format. Thus
when printed out it gets converted to base ten. 012 in octal means the first
column from the right has a value of 2 and the next along has a value of one
times eight. In decimal that adds up to 10.
Answer 45)
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Question 45
Objective 1.2)
1) Error at compile time
The variable i is created at the level of amethod and will not be available
inside the method multi.
Answer 46)
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Question 46
Objective 10.1)
1) Set
The Set interface ensures that its elements are unique, but
does not order the elements. In reality you probably wouldn't create your own
class using the Set interface. You would be more likely to use one of the JDK
classes that use the Set interface such as HashSet or TreeSet.
Answer 47)
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Question 47
Objective 10.1)
4) Vector v=new Vector(100);
v.addElement("99")
A vector can only store objects not primitives. The parameter "99" for the
addElement method pases a string object to the Vector. Option 1) creates a
vector OK but then uses array syntax to attempt to assign a primitive. Option 2
also creates a vector then uses correct Vector syntax but falls over when the
parameter is a primitive instead of an object.
Answer 48)
Objective 8.1)
Back to Question
48
3) The lower part of the word Dolly will be seen at the top of the form
The Second parameter to the drawstring method indicates where the baseline of
the string will be placed. Thus the 3rd parameter of 10 indicates the Y
coordinate to be 10 pixels from the top of the Frame. This will result in just
the bottom of the string Dolly showing up or possibly only the descending part
of the letter y.
Answer 49)
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Question 49)
Objective 9.1)
1) Compile time error referring to a cast problem
This is a bit of a sneaky one as the Math.random method returns a pseudo
random number between 0 and 1, and thus option 3 is a plausible Answer. However
the number returned is a double and so the compiler will complain that a cast is
needed to convert a double to an int.
Answer 50)
Objective 2.3)
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50
1) public void ioCall ()throws IOException{
DataInputStream din = new DataInputStream(System.in);
din.readChar();
}If a method might throw an exception it must either be caught within the
method with a try/catch block, or the method must indicate the exception to any
calling method by use of the throws statement in its declaration. Without this,
an error will occur at compile time.
Answer 51)
Objective 1.2)
Back to Question
51)
3) A compile time error
Because only one instance of a static method exists not matter how many
instance of the class exists it cannot access any non static variables. The JVM
cannot know which instance of the variable to access. Thus you will get an error
saying something like
Can't make a static reference to a non static variable
Answer 52)
Objective 8.1)
Back to Question
52)
2) Create an instance of the GridBagConstraints class, set the weightx field
and then pass the GridBagConstraints instance with the component to the
setConstraints method of the GridBagLayout class.
The Key to using the GridBagLayout manager is the GridBagConstraint class.
This class is not consistent with the general naming conventions in the java API
as you would expect that weightx would be set with a method, whereas it
is a simple field (variable).
If you have a copy of the Roberts and Heller Java2 Guide that says the exam
does not cover the GridBagLayout, this is an error which is corrected in later
versions of the book
Answer 53)
Objective 11.1)
Back to Question
53)
2) Return the name of the parent directory
3) Delete a file
It is surprising that you can't change the current directory. It is not so
surprising that you can't tell if a file contains text or binary information.
Answer 54)
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Question 54)
Objective 7.1
2) Output of One One Two Two
Answer 3 would would be true if the code called the start method instead of
the run method (well it is on my Windows machine anyway, I'm not sure it would
be for ever implementation of Java Threads). If you call the run method directly
it just acts as any other method and does not return to the calling code until
it has finished executing.
Answer 55)
Objective 3.1)
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55)
1) You cannot be certain when garbage collection will run
Although there is a Runtime.gc(), this only suggests that the Java Virtual
Machine does its garbage collection. You can never be certain when the garbage
collector will run. Roberts and Heller is more specific abou this than Boone.
This uncertainty can cause consternation for C++ programmers who wish to run
finalize methods with the same intent as they use destructor methods.
Answer 56)
Objective 8.1)
Back to Question
56)
4) The fill field of the GridBagConstraints class
Unlike the GridLayout manager you can set the individual size of a control
such as a button using the GridBagLayout manager. A little background knowledge
would indicate that it should be controlled by a setSomethingOrOther method, but
it isn't.
If you have a copy of the Roberts and Heller Java2 Guide that says the exam
does not cover the GridBagLayout, this is an error. You can confirm this by
looking at the online errata at
Answer 57)
Objective 10.1)
Back to Question
57)
4) A collection for storing bits as on-off information, like a vector of bits
This is the description given to a bitset in Bruce Eckels "Thinking in Java"
book. The reference to unique sequence of bits was an attempt to mislead because
of the use of the word Set in the name bitset. Normally something called a set
implies uniqueness of the members, but not in this context.
Answer 58)
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Question 58)
Objective 4.1)
4)Compile error: Superclass Class1.Base of class Class1.Class1 not found
Using the package statement has an effect similar to placing a source file
into a different directory. Because the files are in different packages they
cannot see each other. The stuff about File1 not having been compiled was just
to mislead, java has the equivalent of an "automake", whereby if it was not for
the package statements the other file would have been automatically compiled.
Answer 59)
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Question 59)
Objective 6.2)
4) Output of Over.amethod()
The names of parameters to an overridden method is not important, but as the
version of amethod in class Base is set to be private it is not visible within
Over (despite Over extending Base) and thus does not take part in overriding.
Answer 60)
Objective 8.1)
Back to Question
60)
1) Set the gridy value of the GridBagConstraints class to a value increasing
from 1 to 4
Answer 4 is fairly obviously bogus as it is the GridBagConstraints class that
does most of the magic in laying out components under the GridBagLayout manager.
The fill value of the GridBagConstraints class controls the behavior inside its
virtual cell and the ipady field controls the internal padding around a
component.
If you have a copy of the Roberts and Heller Java2 Guide that says the exam
does not cover the GridBagLayout, this is an error. You can confirm this by
looking at the online errata at
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