Original to be found at http://members.theglobe.com/apoddar/questions.html
Q 1. What is the output of the
following
StringBuffer sb1
= new StringBuffer("Amit");
StringBuffer sb2=
new StringBuffer("Amit");
String ss1 = "Amit";
System.out.println(sb1==sb2);
System.out.println(sb1.equals(sb2));
System.out.println(sb1.equals(ss1));
System.out.println("Poddar".substring(3));
Ans:
a) false
false
false
dar
b) false
true
false
Poddar
c) Compiler Error
d) true
true
false
dar
Correct Answer is a)
*****
Look carefully at code and answer the following questions ( Q2
to Q8)
1 import
java.applet.Applet;
2 import java.awt.*;
3 import java.awt.event.*;
4 public
class hello4 extends Applet {
5
public void init(){
6
add(new myButton("BBB"));
7 }
8
public void paint(Graphics screen) {
9 }
10
class myButton extends Button{
11
myButton(String label){
12
super(label);
13
}
14
public String paramString(){
15
return super.paramString();
16
}
17 }
18 public static
void main(String[] args){
19
Frame myFrame = new Frame(
20
"Copyright Amit");
21
myFrame.setSize(300,100);
22 Applet
myApplet = new hello4();
23 Button
b = new Button("My Button");
24 myApplet.add(b);
25 b.setLabel(b.getLabel()+"New");
26 // myButton
b1 =(new hello4()).new myButton("PARAMBUTTON");
27 System.out.println(b1.paramString());
28 myFrame.add(myApplet);
29 myFrame.setVisible(true);
30 myFrame.addWindowListener(new
WindowAdapter(){
31
public void windowClosing(WindowEvent e){
32
System.exit(0);}});
33 }
34 } //End hello4 class.
Q2.
If you run the above program via appletviewer ( defining a HTML
file), You see on screen.
a) Two buttons
b) One button with label
as "BBB"
c) One button with label as "My
ButtonNew"
d) One button with label as "My
Button"
Correct answer is b)
Q3. In the above code if line 26 is uncommented and program runs as standalone application
a)
Compile Error
b) Run time error
c) It will print the the label
as PARAMBUTTON for button b1
Correct answer is c)
Q4
In the code if you compile as "javac hello4.java" following files
will be generated.
a) hello4.class, myButton.class,hello41.class
b)hello4.class, hello4$myButton.class,hello4$1.class
c)hello4.clas,hello4$myButton.class
Correct answer is b)
Q5. If above program is run as a standalone application. How many buttons will be displayed
a)
Two buttons
b) One button with label as "BBB"
c) One button with label as "My
ButtonNew"
d) One button with label as "My
Button"
correct answer is C)
Q6. If from line no 14 keyword "public" is removed, what will happen.( Hint :paramString() method in java.awt.Button is a protected method. (Assume line 26 is uncommented)
a)
Code will not compile.
b) Code will compile but will
give a run time error.
c) Code will compile and no run
time error.
Correct answer is a). As you can not override a method with weaker access privileges
Q7. If from line no 14 keyword "public" is replaced with "protected", what will happen.(Hint :paramString() method in java.awt.Button is a protected method.(Assume line 26 is uncommented)
a)
Code will not compile.
b) Code will compile but will
give a run time error.
c) Code will compile and no run
time error.
Correct answer is c) . As you can access a protected variable in the same package.
Q8.If line no 26 is replaced with Button b1 = new Button("PARAMBUTTON").(Hint :paramString() method in java.awt.Button is a protected method.(Assume line 26 is uncommented)
a)
Code will not compile.
b) Code will compile but will
give a run time error.
c) Code will compile and no run
time error.
Correct answer is a) Because protected variables and methods can not be accssed in another package directly. They can only be accessed if the class is subclassed and instance of subclass is used.
Q9. What is the output of following if the return value is "the value 0 if the argument string is equal to this string; a value less than 0 if this string is lexicographically less than the string argument; and a value greater than 0 if this string is lexicographically greater than the string argument" (Assuming written inside main)
String
s5 = "AMIT";
String s6 = "amit";
System.out.println(s5.compareTo(s6));
System.out.println(s6.compareTo(s5));
System.out.println(s6.compareTo(s6));
Ans
a> -32
32
0
b> 32
32
0
c> 32
-32
0
d> 0
0
0
Correct Answer is a)
Q 10)
What is the output (Assuming written inside
main)
String s1
= new String("amit");
String s2
= s1.replace('m','i');
s1.concat("Poddar");
System.out.println(s1);
System.out.println((s1+s2).charAt(5));
a)
Compile error
b) amitPoddar
o
c) amitPoddar
i
d) amit
i
Correct answer is d)As String is imutable.so s1 is always "amit". and s2 is "aiit".
Q 11)
What is the output (Assuming written inside
main)
String s1
= new String("amit");
System.out.println(s1.replace('m','r'));
System.out.println(s1);
String s3="arit";
String s4="arit";
String s2
= s1.replace('m','r');
System.out.println(s2==s3);
System.out.println(s3==s4);
a)
arit
amit
false
true
b) arit
arit
false
true
c) amit
amit
false
true
d) arit
amit
true
true
Correct answer is a) s3==s4 is true because java
points both s3 and s4 to same memory location in string pool
Q12)
Which one does not extend java.lang.Number
1)Integer
2)Boolean
3)Character
4)Long
5)Short
Correct answer is 2) and 3)
Q13)
Which one does not have a valueOf(String) method
1)Integer
2)Boolean
3)Character
4)Long
5)Short
Correct answer is 3)
Q.14)
What is the output of following (Assuming written
inside main)
String s1
= "Amit";
String s2
= "Amit";
String s3
= new String("abcd");
String s4
= new String("abcd");
System.out.println(s1.equals(s2));
System.out.println((s1==s2));
System.out.println(s3.equals(s4));
System.out.println((s3==s4));
a) true
true
true
false
b) true
true
true
true
c) true
false
true
false
Correct answer is a)
Q15.
Which checkbox will be selected in the following code ( Assume
with main and added to a Frame)
Frame myFrame = new Frame("Test");
CheckboxGroup cbg = new CheckboxGroup();
Checkbox cb1 = new Checkbox("First",true,cbg);
Checkbox cb2 = new Checkbox("Scond",true,cbg);
Checkbox cb3 = new Checkbox("THird",false,cbg);
cbg.setSelectedCheckbox(cb3);
myFrame.add(cb1);
myFrame.add(cb2);
myFrame.add(cb3);
a) cb1
b) cb2,cb1
c) cb1,cb2,cb3
d) cb3
Correct Answer is d) As in a CheckboxGroup only one can be selected
Q16)
Which checkbox will be selected in the following code ( Assume
with main and added to a Frame)
Frame myFrame = new Frame("Test");
CheckboxGroup cbg = new CheckboxGroup();
Checkbox cb1 = new Checkbox("First",true,cbg);
Checkbox cb2 = new Checkbox("Scond",true,cbg);
Checkbox cb3 = new Checkbox("THird",true,cbg);
myFrame.add(cb1);
myFrame.add(cb2);
myFrame.add(cb3);
a) cb1
b) cb2,cb1
c) cb1,cb2,cb3
d) cb3
Correct Answer is d) As in a CheckboxGroup only one can be selected
Q17)
What will be the output of line 5
1 Choice c1
= new Choice();
2 c1.add("First");
3 c1.addItem("Second");
4 c1.add("Third");
5 System.out.println(c1.getItemCount());
a) 1
b) 2
c) 3
d) None of
the above
Correct Answer is c)
Q18)
What will be the order of four items added
Choice c1
= new Choice();
c1.add("First");
c1.addItem("Second");
c1.add("Third");
c1.insert("Lastadded",2);
System.out.println(c1.getItemCount());
a) First,Second,Third,Fourth
b) First,Second,Lastadded,Third
c) Lastadded,First,Second,Third
Correct
ANswer is b)
Q19)
Answer based on following code
1 Choice c1
= new Choice();
2 c1.add("First");
3 c1.addItem("Second");
4 c1.add("Third");
5 c1.insert("Lastadded",1000);
6 System.out.println(c1.getItemCount());
a)
Compile time error
b) Run time
error at line 5
c) No error and line
6 will print 1000
d) No error and line
6 will print 4
Correct ANswer is d)
Q20) Which one of the following does not extends java.awt.Component
a)
CheckBox
b) Canvas
c) CheckbocGroup
d) Label
Correct answer is c)
Q21)
What is default layout manager for panels and applets?
a) Flowlayout
b) Gridlayout
c) BorderLayout
Correct answer is a)
Q22) For awt components which of the following statements are true?
a)
If a component is not explicitly assigned a font, it usese the
same font that it container uses.
b) If a component is not explicitly
assigned a foreground color , it usese the same foreground color
that it container uses.
c) If a component is not explicitly
assigned a backround color , it usese the same background color
that it container uses.
d) If a component is not explicitly
assigned a layout manager , it usese the same layout manager
that it container uses.
correct answer is a),b),c)
Q23)java.awt.Component class method getLocation() returns Point (containg x and y cordinate).What does this x and y specify
a)
Specify the postion of components lower-left component in the
coordinate space of the component's parent.
b) Specify the postion of components
upper-left component in the coordinate space of the component's
parent.
c) Specify the postion of components
upper-left component in the coordinate space of the screen.
correct answer is b)
Q24.
Q. What will be the output of follwing
{
double d1 = -0.5d;
System.out.println("Ceil for
d1 " + Math.ceil(d1));
System.out.println("Floor for
d1 " +Math.floor(d1));
}
Answers:
a) Ceil for d1 0
Floor for
d1 -1;
b) Ceil for d1 0
Floor for
d1 -1.0;
c) Ceil for d1 0.0
Floor for
d1 -1.0;
d) Ceil for d1 -0.0
Floor for
d1 -1.0;
correct answer is d) as 0.0 is treated differently from -0.0
Q25.
What is the output of following
{
float f4 = -5.5f;
float f5 = 5.5f;
float f6 = -5.49f;
float f7 = 5.49f;
System.out.println("Round f4
is " + Math.round(f4));
System.out.println("Round f5
is " + Math.round(f5));
System.out.println("Round f6
is " + Math.round(f6));
System.out.println("Round f7
is " + Math.round(f7));
}
a)Round f4 is -6
Round f5 is 6
Round f6 is -5
Round f7 is 5
b)Round
f4 is -5
Round f5 is 6
Round f6 is -5
Round f7 is 5
Correct
answer is b)
Q26.
Given Integer.MIN_VALUE = -2147483648
Integer.MAX_VALUE = 2147483647
What is the output of following
{
float f4 = Integer.MIN_VALUE;
float f5 = Integer.MAX_VALUE;
float f7 = -2147483655f;
System.out.println("Round f4
is " + Math.round(f4));
System.out.println("Round f5
is " + Math.round(f5));
System.out.println("Round f7
is " + Math.round(f7));
}
a)Round
f4 is -2147483648
Round f5 is 2147483647
Round f7 is -2147483648
b)Round
f4 is -2147483648
Round f5 is 2147483647
Round f7 is -2147483655
correct
answer is a)
//Reason If the argument is negative
infinity or any value less than or equal to the value of Integer.MIN_VALUE,
the result is
equal to the value of Integer.MIN_VALUE.
If the argument
is positive infinity or any value greater than or equal to the
value of Integer.MAX_VALUE, the result is
equal to the value of Integer.MAX_VALUE.
// From JDK api documentation
Q27)
1 Boolean
b1 = new Boolean("TRUE");
2 Boolean
b2 = new Boolean("true");
3 Boolean
b3 = new Boolean("JUNK");
4 System.out.println(""
+ b1 + b2 + b3);
a)
Comiler error
b) RunTime error
c)truetruefalse
d)truetruetrue
Correct answer is c)
Q 28)
In the above question if line 4 is changed to
System.out.println(b1+b2+b3); The output is
a) Compile time error
b) Run time error
c) truetruefalse
d) truetruetrue
Correct
answer is a) As there is no method to support Boolean +
Boolean
Boolean b1 = new Boolean("TRUE");
Think ----->System.out.println(b1);
// Is this valid or not?
Q 29.
What is the output
{
Float f1 = new Float("4.4e99f");
Float f2 = new Float("-4.4e99f");
Double d1 = new Double("4.4e99");
System.out.println(f1);
System.out.println(f2);
System.out.println(d1);
}
a)
Runtime error
b) Infinity
-Infinity
4.4E99
c) Infinity
-Infinity
Infinity
d) 4.4E99
-4.4E99
4.4E99
Correct
answer is b)
Q30
Q. Which of the following wrapper classes can not
take a "String" in constructor
1)
Boolean
2) Integer
3) Long
4) Character
5) Byte
6) Short
correct answer is 4)
Q31.
What is the output of following
Double d2
= new Double("-5.5");
Double d3
= new Double("-5.5");
System.out.println(d2==d3);
System.out.println(d2.equals(d3));
a)
true
true
b) false
false
c) true
false
d) false
true
Correct answer is d)
Q32)
Which one of the following always honors the components's
preferred size.
a) FlowLayout
b) GridLayout
c) BorderLayout
Correct answer is a)
Q33)
Look at the following code
import java.awt.*;
public class
visual extends java.applet.Applet{
static
Button b = new Button("TEST");
public
void init(){
add(b);
}
public
static void main(String args[]){
Frame f = new Frame("Visual");
f.setSize(300,300);
f.add(b);
f.setVisible(true);
}
}
What will happen if above code is run as a standalone application
a)
Displays an empty frame
b) Displays a frame with a button
covering the entire frame
c) Displays a frame with a button
large enough to accomodate its label.
Correct
answer is b) Reason- Frame uses Border Layout which places the
button to CENTRE
(By default) and ignores
Button's preferred size.
Q34
If the code in Q33 is compiled and run via appletviewer
what will happen
a) Displays an empty applet
b) Displays a applet with a button
covering the entire frame
c) Displays a applet with a button
large enough to accomodate its label.
Correct answer is c) Reason- Applet uses FlowLayout which honors Button's preferred size.
Q35.
What is the output
public static
void main(String args[]){
Frame f = new Frame("Visual");
f.setSize(300,300);
f.setVisible(true);
Point p = f.getLocation();
System.out.println("x is " + p.x);
System.out.println("y is " + p.y);
}
a)
x is 300
y is 300
b) x is 0
y is 0
c) x is 0
y is 300
correct
answer is b) Because postion is always relative to parent container
and in this
case Frame
f is the topemost container
Q36)
Which one of the following always ignores the components's
preferred size.
a) FlowLayout
b) GridLayout
c) BorderLayout
Correct answer is b)
Q37)
Consider a directory structure like this (NT or 95)
C:\JAVA\12345.msg
--FILE
\dir1\IO.class -- IO.class is under dir1
Consider the following code
import java.io.*;
public class
IO {
public static void main(String args[]) {
File f = new File("..\\12345.msg");
try{
System.out.println(f.getCanonicalPath());
System.out.println(f.getAbsolutePath());
}catch(IOException e){
System.out.println(e);
}
}
}
What
will be the output of running "java IO" from C:\java\dir1
a) C:\java\12345.msg
C:\java\dir1\..\12345.msg
b)
C:\java\dir1\12345.msg
C:\java\dir1\..\12345.msg
c)
C:\java\dir1\..\12345.msg
C:\java\dir1\..\12345.msg
correct
answer is a) as getCanonicalPath Returns the canonical form
of this File object's pathname. The precise definition of canonical
form is system-dependent, but it usually
specifies an absolute pathname
in which all relative references and references to the current
user directory have been completely resolved.
WHERE AS
getAbsolutePath Returns the absolute
pathname of the file represented by this object. If this object
represents an absolute pathname, then return the pathname. Otherwise,
return a pathname that is a concatenation of the current user
directory, the separator character, and the pathname of this file
object.
Q 38) Suppose we copy IO.class
from C:\java\dir1 to c:\java
What will be the output of running "java IO" from C:\java.
a) C:\java\12345.msg
C:\java\..\12345.msg
b)
C:\12345.msg
C:\java\..\12345.msg
c)
C:\java\..\12345.msg
C:\java\\..\12345.msg
correct answer is b)
Q39) Which one of the following methods of java.io.File throws IOException and why
a)
getCanonicalPath and getAbsolutePath both require filesystem queries.
b) Only getCannonicalPath as
it require filesystem queries.
c) Only getAbsolutePath as it
require filesystem queries.
Correct answer is b)
Q40)
What will be the output if
Consider a
directory structure like this (NT or 95)
C:\JAVA\12345.msg --FILE
\dir1\IO.class -- IO.class is under dir1
import java.io.*;
public class IO {
public static void main(String args[]) {
File f = new File("12345.msg");
String arr[] = f.list();
System.out.println(arr.length);
}
}
a)
Compiler error as 12345.msg is a file not a directory
b) java.lang.NullPointerException
at run time
c) No error , but nothing will
be printed on screen
Correct ansewer is b)
Q41)
What will be the output
Consider a
directory structure like this (NT or 95)
C:\JAVA\12345.msg --FILE
import java.io.*;
public class
IO {
public static void main(String args[]) {
File f1 = new File("\\12345.msg");
System.out.println(f1.getPath());
System.out.println(f1.getParent());
System.out.println(f1.isAbsolute());
System.out.println(f1.getName());
System.out.println(f1.exists());
System.out.println(f1.isFile());
}
}
a)
\12345.msg
\
true
12345.msg
true
true
b)
\12345.msg
\
true
\12345.msg
false
false
c)
12345.msg
\
true
12345.msg
false
false
d) \12345.msg
\
true
12345.msg
false
false
correct answer is d)
Q42)
If in question no 41 the line
File
f1 = new File("\\12345.msg"); is replaced with File f1 = new File("12345.msg");
What will
be the output
a)
12345.msg
\
true
12345.msg
true
true
b)
12345.msg
null
true
12345.msg
true
true
c) 12345.msg
null
false
12345.msg
true
true
d)
\12345.msg
\
true
12345.msg
false
false
Correct
answer is c) More is added to the list, but what I realy need is your help to keep
this information up-to-date and may be it needs correcting in one way
or the other. Please feel free to help me complement these question
and answers drop us an email at this
address. (C) 1998-2001, BMC88 - Personal WebSite of Java Certification
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