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Question 1: Given the following
class definition:
class A {
protected int i;
A(int i) {
this.i = i;
}
}
Which of the following would be a
valid inner class for this class?
Select all valid answers.
a)
class B {
}
b)
class B extends A {
}
c)
class B {
B() {
System.out.println("i = " + i);
}
}
d)
class B {
class A {
}
}
e)
class A {
}
Question 2: What statements are true concerning
the method notify() that is used in conjunction with wait()?
Select all valid answers.
a) if there is more than one thread
waiting on a condition, only the thread that has been waiting the longest is
notified
b) if there is more than one thread
waiting on a condition,there is no way to predict which thread will be notifed
c) notify() is defined in the Thread
class
d) it is not strictly necessary to
own the lock for the object you invoke notify() for
e) notify() should only be invoked
from within a while loop
Question 3: Given the following class:
class Counter {
public int
startHere = 1;
public int endHere
= 100;
public static void
main(String[] args) {
new
Counter().go();
}
void go() {
// A
Thread t = new
Thread(a);
t.start();
}
}
What block of code can you replace
at line A above so that this program will count from startHere to endHere?
Select all valid answers.
a)
Runnable a = new Runnable() {
public void run() {
for (int i =
startHere; i <= endHere; i++) {
System.out.println(i);
}
}
};
b)
a implements Runnable {
public void run() {
for (int i =
startHere; i <= endHere; i++) {
System.out.println(i);
}
}
};
c)
Thread a = new Thread() {
public void run() {
for (int i =
startHere; i <= endHere; i++) {
System.out.println(i);
}
}
};
Question 4: What is written to the standard output
given the following statement:
System.out.println(4 | 7);
Select the one right answer.
a) 4
b) 5
c) 6
d) 7
e) 0
Question 5: Given the following class:
class Counter {
public static void
main(String[] args) {
Thread t = new
Thread(new CounterBehavior());
t.start();
}
}
Which of the following is a valid
definition of CounterBehavior that would make Counter’s main() method count
from 1 to 100, counting once per second?
Select the one right answer.
a)This class is an inner class to Counter:
class CounterBehavior {
for (int i = 1; i
<= 100; i++);
try {
System.out.println(i);
Thread.sleep(1000);
} catch
(InterruptedException x) {}
}
}
b) This class is an inner class to Counter:
class CounterBehavior implements Runnable {
public void run() {
for (int i = 1;
i <= 100; i++);
try {
System.out.println(i);
Thread.sleep(1000);
} catch
(InterruptedException x) {}
}
}
}
c) This class is a top-level class:
static class CounterBehavior implements Runnable {
public void run() {
try {
for (int i =
1; i <= 100; i++) {
System.out.println(i);
Thread.sleep(1000);
}
} catch
(InterruptedException x) {}
}
}
Question 6: Given the following class definition:
class A {
public int x;
private int y;
class B {
protected void
method1() {
}
class C {
private void
method2() {
}
}
}
}
class D extends A {
public float z;
}
What can method2() access directly,
without a reference to another instance?
Select all valid answers.
a) the variable x defined in A
b) the variable y defined in A
c) method1 defined in B
d) the variable z defined in D
Question 7: You have an 8-bit file using the
character set defined by ISO 8859-8. You are writing an application to display
this file in a TextArea. The local encoding is already set to 8859-8. How can
you write a chunk of code to read the first line from this file?
You have three variables accessible
to you:
myfile
is the name of the file you want to read
stream
is an InputStream object associated with this file
s is
a String object
Select all valid answers.
a)
InputStreamReader reader = new InputStreamReader(stream,
"8859-8");
BufferedReader buffer = new BufferedReader(reader);
s = buffer.readLine();
b)
InputStreamReader reader = new InputStreamReader(stream);
BufferedReader buffer = new BufferedReader(reader);
s = buffer.readLine();
c)
InputStreamReader reader = new InputStreamReader(myfile,
"8859-8");
BufferedReader buffer = new BufferedReader(reader);
s = buffer.readLine();
d)
InputStreamReader reader = new InputStreamReader(myfile);
BufferedReader buffer = new BufferedReader(reader);
s = buffer.readLine();
e)
FileReader reader = new FileReader(myfile);
BufferedReader buffer = new BufferedReader(reader);
s = buffer.readLine();
Question 8: How can you write a line of code for
an applet’s init() method that determines how wide the applet is?
Select all valid answers.
a) int width = this.getY();
b) int width = this.getSize().w;
c) int width = getSize();
d) int width = getSize().w;
e) int width = getWidth();
Question 9: For a variable width font, how
"wide" is a TextField created using the expression:
new TextField(20)
Select the one right answer.
a) 20 times the average of all the
characters in the font used for this TextField object
b) 20 times the width of the letter
M
c) 20 times the width of the letter
a
d) 20 inches
e) 20 picas
Question 10: Given this interface definition:
interface A {
int method1(int i);
int method2(int j);
}
which of the following classes
implement this interface and is not abstract?
Select all valid answers.
a)
class B implements A {
int method1() { }
int method2() { }
}
b)
class B {
int method1(int i)
{ }
int method2(int j)
{ }
}
c)
class B implements A {
int method1(int i)
{ }
int method2(int j)
{ }
}
d)
class B extends A {
int method1(int i)
{ }
int method2(int j)
{ }
}
e)
class B implements A {
int method2(int j)
{ }
int method1(int i)
{ }
}
Question 11: Given the following code:
import java.awt.*;
import java.awt.event.*;
public class MyApplet extends java.applet.Applet {
public void init()
{
Button b = new
Button("Button1");
b.addMouseListener(new ClickHandler());
add(b);
}
class ClickHandler
extends MouseAdapter {
public void
mouseClicked(MouseEvent evt) {
// A
}
}
}
What line of code at A writes the
mouse’s horizontal location to the standard output at the time of the event?
Fill in the blank.
Question 12: Given the same code as in question
10, how can you write a line of code at A that will place the Button object
into a variable named mybutton that is already defined to be a reference to a
Button object?
Fill in the blank.
Question 13: Which Listener interface can you
implement to be able to respond to the user hitting the enter key after typing
into a TextField object?
Fill in the blank.
Question 14: What is written to the standard
output as the result of executing the following statements?
Boolean b1 = new Boolean(true);
Boolean b2 = new Boolean(true);
if (b1 == b2)
if (b1.equals(b2))
System.out.println("a");
else
System.out.println("b");
else
if (b1.equals(b2))
System.out.println("c");
else
System.out.println("d");
Select the one right answer.
a) a
b) b
c) c
d) d
Question 15: Which Listener interfaces can you add
to a TextArea object?
a) TextListener
b) ActionListener
c) MouseMotionListener
d) MouseListener
e) ComponentListener
Question 16: What appears in the standard output
if the method named problem() in the code below throws an instance of class
Exception when the method named trythis() is invoked?
public void trythis() {
try {
System.out.println("1");
problem();
} catch
(RuntimeException x) {
System.out.println("2");
return;
} catch (Exception
x) {
System.out.println("3");
return;
} finally {
System.out.println("4");
}
System.out.println("5");
}
Select all valid answers.
a) "1"
b) "2"
c) "3"
d) "4"
e) "5"
Question 17: What is the type of the Event object
passed to the mouseDragged() method defined in a class that implements java.awt.event.MouseMotionListener
(that is, what is the class name for the argument)?
Fill in the blank.
Question 18: Examine the following switch block:
char mychar = 'c';
switch (mychar) {
default:
case 'a':
System.out.println("a"); break;
case 'b':
System.out.println("b"); break;
}
Which of the following questions are
definitely true?
Select all valid answers.
a) This switch block is illegal,
because only integers can be used in the switch statement.
b) This switch block is fine.
c) This switch block is illegal,
because the default statement must come last.
d) When this code runs, nothing is
written to the standard output.
e) When this code runs, the letter
"a" is written to the standard output.
Question 19: What keyword must appear in a method declaration
(followed by the name of the exception) when that method might cause an
exception to be thrown and that method does not handle the exception?
Fill in the blank.
Question 20: Which statements accurately describe
the following line of code?
Select all valid answers.
String[][] s = new String[10][];
a) This line of code is illegal.
b) s is a two-dimensional array
containing 10 rows and 10 columns
c) s is an array of 10 arrays.
d) Each element in s is set to
""
e) Each element in s is uninitialized
and must be initialized before it is referenced.
Question 21: What will happen if you try to
compile and run the following class?
class Test {
static int myArg =
1;
public static void
main(String[] args) {
int myArg;
System.out.println(myArg);
}
}
Select the one right answer.
a) This code compiles and displays 0
in the standard output when run.
b) This code compiles and displays 1
in the standard output when run.
c) This code does not compile
because you cannot define a local variable named the same as a static variable.
d) This code does not compile
because the local variable is used before it is initialized.
Question 22: Which declarations for the main()
method in a stand-alone program are NOT valid?
Select all valid answers.
a) public static void main()
b) public static void main(String[]
string)
c) public static void main(String
args)
d) static public int main(String[]
args)
e) static void main(String[] args)
Question 23: Which of the following identifiers
are ILLEGAL?
Select all valid answers.
a) #_pound
b) _underscore
c) 5Interstate
d) Interstate5
e) _5_
Question 24: If the user invokes a stand-alone
application by typing:
java YourApp 1 2 3
and the main() method defines its
String[] parameter as args, how can you access the number 2 using args?
Fill in the blank.
Question 25: Which interface implementations can
you add as listeners for a TextField object?
Select all valid answers.
a) ActionListener
b) FocusListener
c) MouseMotionListener
d) WindowListener
e) ContainerListener
Question 26: What must be true for the RunHandler
class so that instances of RunHandler can be used as written in the code below:
class Test {
public static void
main(String[] args) {
Thread t = new
Thread(new RunHandler());
t.start();
}
}
Select all valid answers.
a) RunHandler must implement the
java.lang.Runnable interface.
b) RunHandler must extend the Thread
class.
c) RunHandler must provide a run()
method declared as public and returning void.
d) RunHandler must provide an init()
method.
Question 27: To determine if you can invoke
addContainerListener() for a component referenced using a variable named c,
which expression(s) can you evaluate that will give you a true or false answer
to this questions?
Select all valid answers.
a) c == Container
b) c.equals(Class.Container)
c) c instanceof Container
d) c instanceof Component
e) c implements Container
Question 28: Write a statement for a constructor
that invokes the no-args, default constructor in its superclass.
Fill in the blank.
Question 29: What is written to the standard
output given the following statement:
System.out.println(4 & 7);
Select the one right answer.
a) 4
b) 5
c) 6
d) 7
e) 0
Question 30: What will the following block of code
write to the standard output when it is executed?
int i = 3;
int j = 0;
double k = 3.2;
if (i < k)