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Java Certification Questions from Apollo
Which of these is the correct declaration for main?
A. public static void main();
B. public void static main(String []args);
C. public static void main(String args);
D. public static void main(String args[]);
Which code fragments would correctly identify the number of arguments passed via the command line to a 18218j917s Java application, excluding the name of the class that is being invoked? What is wrong with the code fragments that are incorrect and what errors do they produce?
A. int count = args.length;
B. int count = args.length - 1;
C. int count = 0;
while (args[count] != null)
count ++;
D. int count=0;
while (!(args[count].equals("")))
count ++;
Represent the value of -192 in binary format, outlining the steps.
What is the value of -7%-2?
A. 1
B. -1
C. 0
What is the value of 8.7%
A. 1.6
B. 1.8
C. 1.1
D. 6.4
What will be the resulting types of the variables in the following operations:
A. a=x+y x char, y char
B. a=x+y x long, y int
C. a=x/y x byte, y char
D. a=x%y x int, y char
E. a=x&y x byte, y short
Which of the following operations are legal in Java? x,y are both boolean
A. f(x==y);
B. x=x-y;
C. x=x&&y;
D. x=~y;
E. x^=y;
Which of the following expressions are legal and which are not? Give your reasons in each case.
A. byte B=(byte)x; x boolean
B. x=(char)(x-y); x char
C. f(x&&y); x char
D. x=(char)(x>>1); x char
E. boolean b=(boolean) x; x char
Which of the following expressions are legal and which are not? Give your reasons in each case.
A. x=(byte)(x % y); x byte
B. x=(byte)(x>>1); x byte
C. x&=y;
D. boolean b=(boolean)x; x byte
Which of the following expressions are legal and which are not? Give your reasons in each case.
A. x=x+y; x,y float
B. f(x<y); x,y float
C. x=x&y; x,y float
D. x=x<<1; x,y float
E. byte z=(byte)x - y; x,y byte
What is the difference between the following 2 fragments of code and which couldcause a runtime exception?
A. if (s!=null) & (s.length()>20))
B. if (s!=null) && (s.length()>20))
Which of the following code fragments are legal and which are not? Explain.
A.
package sportinggoods;
class Ski
}
package sportinggoods;
class DownhillSki extends Ski
}
B.
package Transport;
class Vehicle
}
package Transport;
class Car extends Vehicle
}
C.
In
same file: class Vehicle
}
class Car extends Vehicle
}
D.
In
same file: class Ski
}
class DownhillSki extends Ski
}
Which of the following code fragments are legal and which are not? Explain.
A.
public final class FootballGame
}
class AmericanFootballGame extends FootballGame
}
B.
public
class FootballGame
}
C.
public
class FootballGame
}
D.
public class FootballGame
}
class AmericanFootballGame extends FootballGame
}
Which of the following code fragments are legal and which are not? Explain.
A.
public class SportsTournament
void kickoffgame()
}
class WorldCup extends SportsTournament
{
void finalgame()
}
B.
abstract class Animal
public abstract void feed()
}
class Mammal extends Animal
{
void travel()
}
C.
interface
Animal {
void travel()
void feed()
}
class Mammal implements Animal {
void travel()
}
D.
abstract
public class Animal {
abstract void travel()
abstract void feed()
}
class Mammal extends Animal
{
void travel()
void feed()
} (2 things wrong with this !!)
Which of the following code fragments are legal and which are not? Explain.
A. class FootballTeam
B. class FootballTeam
C.
import
java.awt.*;
public class Screen extends Frame
public static void main(String args[])
}
D.
class Rodent {
static void scavenge()
}
class Rat extends Rodent {
void scavenge()
}
E.
class
Store {
void countItems()
static void main(String args[])
Which of the following code fragments are legal and which are not? Explain.
A.
float
f=1.0;
int i=1;
byte b=i+f;
B.
int i=5;
long l=7;
float f=i*l;
C.
int i=5;
void calculate(float f)
calculate(i);
D.
byte
b;
char c;
c='k';
b=c;
E.
int i=1;
boolean negate(boolean b)
negate(i);
Which of the following code fragments are legal and which are not? Explain.
A.
double
d;
short s;
d=1.456;
s=d;
B.
double
d=1.78;
float exponentiate(float f)
exponentiate(d);
C.
boolean B=true;
int i=1;
B=i;
D.
char
c='6';
int i=9;
int add(int x,int y);
add(c,i);
E.
boolean b=false;
int i=0;
b=(boolean)i;
What will be the result of the following code fragment:
short s=517;
byte b=(byte)s;
long l=233;
int i=(int) l;
System.out.println("b=" + b +
";i=" + i);
A. b=517;i=233
B. b=517;i=0
C. b=5;i=0
D. b=5;i=233
Which of the following code fragments are legal and which are not? Explain.
A.
class
Fruit {
public Fruit()
}
public class
public
public static void main(String []args)
}
B.
class
Fruit {
public Fruit()
}
public class
public
public static void main(String []args)
}
C.
interface
Fruit
public class Apple implements Fruit {
public Apple()
public static void main(String []args)
}
D.
interface
Fruit
public class Apple implements Fruit {
public Apple()
public static void main(String []args)
}
E.
interface
Fruit
class Apple implements Fruit {
public Apple()
}
class
public
}
public class MyFruit
}
Which of the following code fragments are legal and which are not? Explain.
A.
int i;
for (i=5,int
j=10; i<10;j--)
B.
int i,j;
for
(i=0,j=10;i<10, j>0;i++,j--)
C.
int i,k;
for
(i=0,k=9;(i<10 && k>0);i++,j--)
D.
int i,j;
for
(i=0;j=10;i<10;i++,j--)
Which of the following code fragments are legal and which are not? Explain.
float
x;
...
switch(x)
long
y;
...
switch(y)
byte
x;
...
switch(x)
int x=1;
int y=2;
int z=3;
int c;
...
switch(c)
short
x;
...
switch(x)
Which of the following code fragments are legal and which are not? Explain.
public
static void g()
try catch(Exception e)
public
static void g()
try catch(Exception e)
public
static void g() throws Throwable{
try catch(Exception e)
public static void main(String []args) catch(Exception e)
}
What is the output for this code fragment?
public class
Rethrow
public static void main(String []args) catch(Exception e)
Originates
from g()
Caught in main
java.lang.Exception: thrown from g()
at Rethrow.g(Rethrow.java:5)
at Rethrow.main(Rethrow.java:10)
Caught
in main
java.lang.Exception: thrown from g()
at Rethrow.g(Rethrow.java:5)
at Rethrow.main(Rethrow.java:10)
Originates
from g()
Caught in main
java.lang.Exception: thrown from g()
at Rethrow.g(Rethrow.java:5)
at Rethrow.main(Rethrow.java:10)
java.lang.NullPointerException: from main
at Rethrow.main(Rethrow.java:
15)
Originates
from g()
Caught in main
thrown from g()
at Rethrow.g(Rethrow.java:5)
at Rethrow.main(Rethrow.java:10)
from main
at Rethrow.main(Rethrow.java:
15)
Which of the following code fragments are legal and which are not? Explain.
abstract class Shape {
Shape() throws ZeroSizeException
abstract void draw() throws ZeroSizeException;
}
class Circle
void getCircumference()
throws ZeroSizeException, NegativeRadiusException
abstract class Shape {
Shape() throws ZeroSizeException
abstract void draw() throws ZeroSizeException;
}
class Circle {
void draw()
void getCircumference()
throws ZeroSizeException, NegativeRadiusException
}
abstract class Shape {
Shape() throws ZeroSizeException
abstract void draw() throws ZeroSizeException;
}
class Circle {
void draw() throws ZeroSizeException, NegativeRadiusException
}
class
Mammal {
Mammal() throws ColdBloodedException
void GiveBirth()
}
interface CanFly
class Bat extends Mammal implements CanFly {
Bat() throws ColdBloodedException, NoWingsException
void GiveBirth()
}
class
Mammal {
Mammal() throws ColdBloodedException
void GiveBirth()
}
interface CanFly
class Bat extends Mammal implements CanFly {
Bat() throws NoWingsException
void GiveBirth()
void fly()
}
class
ColdBloodedException extends Exception
class LaysEggsException extends Exception
class Mammal
{
Mammal()
throws ColdBloodedException, LaysEggsException
void GiveBirth()
}
class VariableBodyTemperature extends ColdBloodedException
interface CanFly
class Bat extends Mammal implements CanFly {
Bat() throws VariableBodyTemperature, NoWingsException
void GiveBirth()
void fly()
}
Which of the following code fragments are legal and
which are not? Explain.
public class
BaseClass {
BaseClass()
public void method() throws IOException
}
public
class CaseOne extends BaseClass
{
CaseOne()
public void method() throws IOException
}
public
class CaseTwo extends BaseClass
{
CaseTwo()
public void method()
}
public
class CaseThree extends BaseClass
{
CaseThree()
public void method() throws EOFException,MalformedURLException
}
public
class CaseFour extends BaseClass
{
CaseFour()
public void method() throws IOException, IllegalAccessException
}
public
class CaseFive extends BaseClass
{
CaseFive()
public void method() throws Exception
}
Which of the following code fragments are legal and which are not? Explain.
public
class StockServer {
public StockServer(String company, int Shares,double currentPrice, double cashOnHand)
public double buy(int numberOfShares,
double pricePerShare)
public float buy(int numberOfShares,
double pricePerShare)
}
public
class StockServer {
public StockServer(String company, int Shares,double currentPrice, double cashOnHand)
public double buy(int numberOfShares,
double pricePerShare)
public float buy(long numberOfShares, double pricePerShare)
}
public
class StockServer {
public StockServer(String company, int Shares,double currentPrice, double cashOnHand)
public double buy(int numberOfShares,
double pricePerShare)
public double buy(int numberOfShares,
float pricePerShare)
}
public
class StockServer {
public StockServer(String company, int Shares,double currentPrice, double cashOnHand)
public double buy(int numberOfShares,
double pricePerShare)
public double buy(double pricePerShare, int numberOfShares)
}
For each of the following code fragments, pleae indicate which has an overriden vs. overloaded method and explain why.
abstract class Shape
class Circle extends Shape
void draw(double x,double y, double radius)
}
abstract class Shape
class Circle extends Shape
void draw()
}
abstract class Mammal
class Dog extends Mammal {
public Dog ()
Dog giveBirth()
}
abstract class Mammal
class Dog extends Mammal {
public Dog ()
Dog giveBirth(int no_of_pups)
}
Which of the following code fragments are legal and which are not? Explain.
class
MusicWork
class ClassicalWork extends MusicWork
class
MusicWork
class ClassicalWork extends MusicWork
class
MusicWork
class ClassicalWork extends MusicWork
class
MusicWork
MusicWork(String name)
class
MusicWork
MusicWork(String name)
MusicWork(String composer)
class
MusicWork
MusicWork(String name)
If you create a non-default derived constructor and don't call the base class constructor will the compiler call the default base class constructor automatically? (Assume that the default constructor is defined for the base class). What about if it is not defined? What about the case of a default derived constructor, does the compiler call the default base class constructor (Eckel Chap 6).
Which of the following code fragments are legal and which are not? Explain.
public
class Outer
}
public void CreateInner()
}
public
class Outer
}
public void CreateInner()
}
public
class Outer
}
public void CreateInner()
}
public
class Outer
public class Inner
public void CreateInner()
}
Which of the following code fragments are legal and
which are not? Explain.
public class
Outer {
public static void main()
public void go(int w,final int z)
class Inner
}
Inner that=new Inner();
that.method;
}
}
Which of the following code fragments are legal and which are not? Explain.
public
class NewThread extends Thread
}
public
class SomeStuff
}
public
class SomeStuff
}
public
void DoStuff
}
public
class NewThread extends Thread
}
Which of the following code fragments are legal and which are not? Explain.
public void doMath
public void getMax
public void getTan
Which of the following code fragments are legal and which are not? Explain.
Character c= new Character("x");
int primitive=1234;
Integer wrappedInt=new Integer(primitive);
int primitiveInt=123;
Float wrappedFloat=new Float(primitiveInt);
Vector
v=new Vector();
for (int i=0;i<10;i++)
v[i]=i;
Long wLong=new Long("here");
Boolean wBoolean=new Boolean("junk");
Given the following code fragments, which of the following a,b,c,d are true?
String
s1="Compare me";
String s2="Compare me";
if (s1.equals(s2)) else
String
s1="Compare me";
String s2="Compare me";
if (s1==s2) else
a) Both I and
II print Failure
b) Both I and II print Success
c) I print Success, II prints Failure
d) I prints Failure, II prints Success
Given the following code fragments, which of the following a,b,c,d are true?
String
s1=new String("Compare me");
String s2=new String("Compare me");
if (s1.equals(s2)) else {
System.out.println("Failure");
String
s1=new String("Compare me");
String s2=new String("Compare me");
if (s1==s2) else
a) Both I and
II print Failure
b) Both I and II print Success
c) I print Success, II prints Failure
d) I prints Failure, II prints Success
List the 6(8) component methods you should know for the exam, and explain what they do.
Is a CheckBoxGroup a component? If not, what is it?
List the 4 elements that can populate a menu.
Which component is the only one allowed to contain a menu bar?
For a newly constructed frame, list the methods to be called to make it visible, in order.
List the 4 non-superclass container classes.
List the steps needed to create a menu bar containing a pull-down menu in order.
If the foreground and background color of a component is not set, what colors does it take on?
List the 11 visual components there are.
Explain how fonts are displayed in TextField and TextArea.
How do you release the non-memry resources of a frame?
Draw the inheritance diagram for Applet, Frame and Panel inheriting from Container.
What are the default Layout Managers for
Applet
Panel
Frame ?
Does calling setBounds ) have any effect on a component? Give a reason why or why not.
Define the behavior of each of the Layout maangers FlowLayout, GridLayout and BorderLayout wrt. the preferred size of a component.
Define the interface for the constructor of each of these Layout managers:
FlowLayout
GridLayout
BorderLayout
Define the strategy for adding a listener to a component and give an example.
Define the strategy for explicitly enabling events for a component and give an example.
State the circumstances under which the GUI thread spontaneously calls paint(), with no impetus from the program.
Why is there a need for the repaint(0 method and what does it do?
Topics
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Exceptions
The need for an exception specification when an exception is thrown from a method, even within the confines of a trycatch block.
No need for an exception specification when the exception thrown is a RuntimeException.
Need to specify an exception specification for Throwable for any calling method in the call stack above a method that throws an exception object using fillInStackTrace()
Exceptions.
Correct form of output when System.out.println(), e.printStackTrace() is called, also if a Runtime Exception
gets all the way to main without being called, printStackTrace()
is called for that exception as the program exits.
Exception Restrictions
Method in derived class not in base class that throws exception.
Method in derived class choosing not to throw any exceptions, even if base class version does
Derived method in derived class/interface trying to add to exception interface from that of base class.
Constructor in derived class/interface throwing additional exceptions to that in the base class.
Constructor in derived class/interface throwing additional exceptions to that in the base class, but not declaring base-class exceptions in exception specification.
Derived Class Method that uses an exception derived from that used by the base-class version.
If you're dealing with a derived class object, which exceptions are you forced to catch? What if the derived class object is upcast to the base type?
Exceptions
Objects and Classes
The return type of an method is not sufficinet enough to guarantee overloading. The arguments
must be of different type/order.
Objects and Classes.
An overloaded method must be strict. For a subclass method that overrides a
method in its parent class, is it legal to return a type which is the subtype
of the class that is returned by the overriden method
in the parent class?
Objects and Classes
Constructors - non-default derived class constructors.
Objects and Classes
Constructors - non-default derived class constructors.
Inner classes
this reference and the construction of inner classes.
""
Accessibility of enclosing class variables from within static inner class.
""
Inner classes and the final keyword.
Formal parameter, non-final
Formal parameter, final
Local variable, non-final
Local variable, final
Threads
java.lang.Math class
java.lang wrapper classes.
...
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Components
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Layout Managers
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Events
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Painting
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Oleg Melnikov Questions
Given the following definition:
String s = null;
Which code fragment will cause an object of type NullPointerException
to be constructed:
A. [ ] if ((s != null) & (s.length)>0));
B. [ ] if ((s != null) && (s.length)>0));
C. [ ] if ((s != null) | (s.length)>0));
D. [ ] if ((s != null) || (s.length)>0));
In Heller's book, it states that for object reference
casting, the new typemust be a superclass/interface
of the class being converted, otherwise a runtime class cast exception will
result. But consider the following code fragment:
abstract class Shape
class Circle extends Shape {
public Circle()
void draw()
}
class Square extends Shape {
public Square()
void draw()
}
class Triangle extends Shape {
public Triangle()
void draw()
}
public class MyShapes
public BaseClass(String s)
}
Then I define a subclass of the above class:
public
Subclass extends BaseClass
My question is this:
Am I compelled to make the call to super(s) in the above constructor for SubClass(String s)? If not, and I do not make the call,
will the compiler on its own, call the default base constructor super() for me, since I have defined it?
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