Deck 11: Exceptions

Question 1

Use the code below to answer the following questions. Note that the catch statements in the code are not implemented, but you will not need those details. Assume filename is a String, x is an int, a is a double array and i is an int. Use the comments i1, i2, i3, e1, e2, e3, e4, e5 to answer the questions (i for instruction, e for exception handler).
try
{
BufferedReader infile = new BufferedReader(new FileReader(filename)); // i1
int x = Integer.parseInt(infile.readLine( )); // i2
a[++i] = (double) (1 / x); // i3
}
catch (FileNotFoundException ex) {...} // e1
catch (NumberFormatException ex) {...} // e2
catch (ArithmeticException ex) {...} // e3
catch (ArrayIndexOutOfBounds ex) {...} // e4
catch (IOException ex) {...} // e5
An exception raised by the instruction in i1 would be caught by the catch statement labeled

A) e1
B) e2
C) e5
D) either e1 or e5
E) either e1, e4, or e5

Answer 1

D
Explanation: D) The BufferedReader instruction tries to open an input stream to a given file. If the filename is incorrect, a FileNotFoundException is thrown. If some other unexpected IO situation exists, such as no disk in the disk drive or invalid stream, then an IOException is thrown.

Question 2

For the questions below, use the following skeletal code.
public static void main(String[ ] args)
{
try
{
ExceptionThrowerCode etc = new ExceptionThrowerCode( );
etc.m1( );
etc.m2( );
}
catch (ArithmeticException ae) { ... }
}
public class ExceptionThrowerCode
{
...
public void m1( )
{
...
}
public void m2( )
{
try
{
m3( );
}
catch(ArithmeticException ae) {...}
catch(NullPointerException npe) {...}
}
public void m3( )
{
try
{
...
}
catch(ArithmeticException ae) {...}
}
}
If a NullPointerException arises in the try statement in m1

A) it is caught in main
B) it is caught in m1
C) it is caught in m2
D) it is caught in m3
E) it is not caught leading to the program terminating

Answer 2

E
Explanation: E) The method m1 has no catch statements at all, so any exception is propagated to the calling method, main. The method main only has a catch statement for an ArithmeticException, so the NullPointerException is not caught resulting in the program terminating.

Question 3

In order to have some code throw an exception, you would use which of the following reserved words?

A) throw
B) throws
C) try
D) Throwable
E) goto

Answer 3

A
Explanation: A) The reserved word throw is used to throw an exception when the exception is detected, as in: if (score < 0) throw new IllegalTestScoreException("Input score " + score + " is negative");

Question 4

NullPointerException and ArithmeticException are both derived from which class?

A) Error
B) Exception
C) RuntimeException
D) IllegalAccessException
E) CheckedException

Question 5

System.err is a(n)

A) input stream
B) GUI dialog box that indicates when an error has arisen
C) object
D) Error subclass
E) RuntimeException subclass

Question 6

Which of the following messages passed to the String str could throw a StringIndexOutOfBoundsException?

A) str.length( )
B) str.charAt(2);
C) str.replace('a', 'A');
D) str.equals(str);
E) any of the above could throw a StringIndexOutOfBoundsException

Question 7

A processing stream is a data stream that

A) can manage both input streams and output streams at the same time
B) performs some manipulation or process on the data
C) can only manage input streams
D) operates on input and output devices but not files
E) can manage byte streams and character streams at the same time

Question 8

An exception can produce a "call stack trace" which lists

A) the active methods in the order that they were invoked
B) the active methods in the opposite order that they were invoked
C) the values of all instance data of the object where the exception was raised
D) the values of all instance data of the object where the exception was raised and all local variables and parameters of the method where the exception was raised
E) the name of the exception thrown

Question 9

The idea that an object can exist separate from the executing program that creates it is called

A) transience
B) static
C) persistence
D) serialization
E) finality

Question 10

For the questions below, use the following skeletal code.
public static void main(String[ ] args)
{
try
{
ExceptionThrowerCode etc = new ExceptionThrowerCode( );
etc.m1( );
etc.m2( );
}
catch (ArithmeticException ae) { ... }
}
public class ExceptionThrowerCode
{
...
public void m1( )
{
...
}
public void m2( )
{
try
{
m3( );
}
catch(ArithmeticException ae) {...}
catch(NullPointerException npe) {...}
}
public void m3( )
{
try
{
...
}
catch(ArithmeticException ae) {...}
}
}
If an ArithmeticException arises in the try statement in m3

A) it is caught in main
B) it is caught in m1
C) it is caught in m2
D) it is caught in m3
E) it is not caught leading to the program terminating

Question 11

Use the code below to answer the following questions. Note that the catch statements in the code are not implemented, but you will not need those details. Assume filename is a String, x is an int, a is a double array and i is an int. Use the comments i1, i2, i3, e1, e2, e3, e4, e5 to answer the questions (i for instruction, e for exception handler).
try
{
BufferedReader infile = new BufferedReader(new FileReader(filename)); // i1
int x = Integer.parseInt(infile.readLine( )); // i2
a[++i] = (double) (1 / x); // i3
}
catch (FileNotFoundException ex) {...} // e1
catch (NumberFormatException ex) {...} // e2
catch (ArithmeticException ex) {...} // e3
catch (ArrayIndexOutOfBounds ex) {...} // e4
catch (IOException ex) {...} // e5
An exception raised by the instruction in i2 would be caught by the catch statement labeled

A) e1
B) e2
C) e3
D) e5
E) either e2 or e5

Question 12

Which of the following is not True of the RuntimeExceptions class?

A) All RuntimeExceptions throw checked exceptions
B) All RuntimeExceptions are Throwable objects
C) RuntimeException has child classes ArithmeticException and NullPointerException
D) RuntimeException objects are not Error objects
E) All of the above are True

Question 13

Character streams manage

A) byte-sized data
B) binary data
C) Unicode characters
D) ASCII characters
E) compressed data

Question 14

The Scanner class provides an abstraction for input operations by

A) using try and catch statements to catch any IOException instead of throwing the Exception elsewhere
B) parsing input lines into individual tokens
C) performing conversion operations from String to the appropriate type as specified in the Scanner message
D) inputting from the standard input stream if create is called using System.in
E) all of the above

Question 15

A Java program can handle an exception in several different ways. Which of the following is not a way that a Java program could handle an exception?

A) ignore the exception
B) handle the exception where it arose using try and catch statements
C) propagate the exception to another method where it can be handled
D) throw the exception to a pre-defined Exception class to be handled
E) all of the above are ways that a Java program could handle an exception

Question 16

Use the code below to answer the following questions. Note that the catch statements in the code are not implemented, but you will not need those details. Assume filename is a String, x is an int, a is a double array and i is an int. Use the comments i1, i2, i3, e1, e2, e3, e4, e5 to answer the questions (i for instruction, e for exception handler).
try
{
BufferedReader infile = new BufferedReader(new FileReader(filename)); // i1
int x = Integer.parseInt(infile.readLine( )); // i2
a[++i] = (double) (1 / x); // i3
}
catch (FileNotFoundException ex) {...} // e1
catch (NumberFormatException ex) {...} // e2
catch (ArithmeticException ex) {...} // e3
catch (ArrayIndexOutOfBounds ex) {...} // e4
catch (IOException ex) {...} // e5
An exception that could also arise in the try statement that does not have an associated catch statement is

A) ClassNotFoundException
B) IllegalArgumentException
C) NegativeArraySizeException
D) NullPointException
E) OutOfMemoryException

Question 17

For the questions below, use the following skeletal code.
public static void main(String[ ] args)
{
try
{
ExceptionThrowerCode etc = new ExceptionThrowerCode( );
etc.m1( );
etc.m2( );
}
catch (ArithmeticException ae) { ... }
}
public class ExceptionThrowerCode
{
...
public void m1( )
{
...
}
public void m2( )
{
try
{
m3( );
}
catch(ArithmeticException ae) {...}
catch(NullPointerException npe) {...}
}
public void m3( )
{
try
{
...
}
catch(ArithmeticException ae) {...}
}
}
If a NullPointerException arises in the try statement in m3

A) it is caught in main
B) it is caught in m1
C) it is caught in m2
D) it is caught in m3
E) it is not caught leading to the program terminating

Question 18

Assume Exceptionname is a checked exception. If a method uses a class that can generate Exceptionname, then either the method must include try and catch statements where a catch statement catches Exceptionname, or the method header must include the statement

A) throw Exceptionname
B) throws Exceptioname
C) catch Exceptionname
D) catches Exceptionname
E) implements Exceptionname

Question 19

Use the code below to answer the following questions. Note that the catch statements in the code are not implemented, but you will not need those details. Assume filename is a String, x is an int, a is a double array and i is an int. Use the comments i1, i2, i3, e1, e2, e3, e4, e5 to answer the questions (i for instruction, e for exception handler).
try
{
BufferedReader infile = new BufferedReader(new FileReader(filename)); // i1
int x = Integer.parseInt(infile.readLine( )); // i2
a[++i] = (double) (1 / x); // i3
}
catch (FileNotFoundException ex) {...} // e1
catch (NumberFormatException ex) {...} // e2
catch (ArithmeticException ex) {...} // e3
catch (ArrayIndexOutOfBounds ex) {...} // e4
catch (IOException ex) {...} // e5
An exception raised by the instruction in i3 would be caught by the catch statement labeled

A) e2
B) e3
C) e4
D) either e3 or e4
E) either e2, e3, or e4

Question 20

A finally clause will execute

A) only if the try statement that precedes it does not throw an exception
B) only if the try statement that precedes it throws an exception that is caught
C) only if the try statement that precedes it throws an exception that is not caught
D) only if the try statement that precedes it throws an exception, whether it is caught or not
E) in any circumstance

Question 21

A disabled component is

A) one that is grayed out
B) one that no longer is active
C) one that is still visually apparent, but no longer functions if clicked
D) provides an indication of functionality that is not currently available
E) all of the above

Question 22

Which statement is True about BufferedWriters

A) BufferedWriters are used because they improve runtime efficiency
B) BufferedWriters are used because they improve compile time efficiency
C) BufferedWriters can be used with input streams as well as with output streams
D) using a BufferedWriter obviates the necessity for catching IOExceptions
E) none of the above

Question 23

Which of the following classes would you use to open a GUI dialog box, which is then used to select a file to open?

A) JOptionPane
B) JTextArea
C) showOpenDialog
D) JFileChooser
E) JFileReader

Question 24

All run-time Errors throw Exceptions.

Question 25

When a program terminates because a thrown exception is not handled, the program

A) starts up again automatically
B) opens a dialog box, which asks the user whether the program should start again, end, or enter a debugging mode
C) saves all output to a disk file called the "runStackTrace.txt"
D) opens a dialog box for the user to specify a disk file name, and all output is stored to that disk file
E) outputs a message indicating what and where the exception was thrown

Question 26

If an exception is thrown and is not caught anywhere in the program, then the program terminates.

Question 27

The difference between a checked and an unchecked exception is

A) checked exceptions need not be listed in a throws clause
B) unchecked exceptions must be listed in a throws clause
C) neither kind of exception follows the rules of exception propagation
D) an unchecked exception requires no throws clause
E) a checked exception always must be caught by a try block; an unchecked exception does not

Question 28

Programmers can define their own Exceptions by extending the Exception class or one of the descendants of the Exception class.

Question 29

The showDialog method is part of which class?

A) JOptionPane
B) JColorChooser
C) JTextArea
D) Scanner
E) all of the above

Question 30

PrintWriter is a better output stream class that PrintStream because PrintWriter

A) has both print and println methods and PrintStream only has print
B) can output both byte and character streams and PrintStream can only output byte streams
C) has error checking mechanisms as part of the class and PrintStream does not
D) will not throw checked exceptions and PrintStream will
E) all of the above

Question 31

The term "exception propagation" means

A) an exception is caught by the first catch clause
B) an exception not caught by the first catch clause is caught by an outer (enclosing) catch clause
C) exceptions are caught, sequentially, by catch clauses in the current try block
D) exceptions always are caught by the outermost try block
E) none of the above

Question 32

A Timer object generates ________ at regular intervals.

A) ActionEvents
B) MouseEvents
C) RuntimeExceptions
D) non-throwable Exception
E) KeyEvents

Question 33

A try statement must have at least one catch statement, but could have many catch statements, and may or may not have a finally clause.

Question 34

A mnemonic is

A) always a single character
B) can be a collection of characters and/or other keys
C) represents an inactive or disabled component
D) can be used instead of a tool tip
E) none of the above

Question 35

A Swing tool tip is

A) a mechanism to aid the programmer during the creation of the source code for a program
B) a short line of text that appears momentarily when the cursor is rested momentarily on a component
C) a graphic that appears when the cursor is rested momentarily on a component
D) available to AWT components as well as to Swing components
E) none of the above

Question 36

Assume infile is a BufferedReader for a textfile and that the textfile is empty. What is returned from the message infile.readLine( ); ?

A) 0
B) null
C) a special character known as the End-of-file marker (EOF)
D) none of the above, the message causes a NullPointerException to be thrown
E) none of the above, the message causes a EndOfFileException to be thrown

Question 37

A method that uses the Scanner class to obtain input does not require either catching or throwing an IOException. This is because

A) the Scanner class does not call upon any classes that throw checked exceptions
B) the Scanner class' methods call input methods in try statements and catch IOExceptions so that they are handled directly in the Scanner class
C) the Scanner class uses JOptionPane dialog boxes instead of java.io classes so that it does not have to deal with IOExceptions
D) the Scanner class overrides the class IOException making it an unchecked exception
E) none of the above, methods do require handling IOException even if thrown by a method in a Scanner class

Question 38

In order to define a keyboard input object, keyboard, you could use the instruction:
BufferedReader keyboard = new BufferedReader(System.in);

Question 39

The Timer object should be used to support which of the following types of applications?

A) animation
B) GUI input from the mouse
C) any applet application
D) input from and output to text files
E) any application that waits for user input via the keyboard

Question 40

To implement the KeyListener interface, you must implement all of the following methods except for which one?

A) keyEvent
B) keyPressed
C) keyTyped
D) keyReleased
E) all of the above methods must be implemented

Question 41

The difference between a scroll pane and a split pane is that the former includes a dividing line while the latter does not.

Question 42

Write a set of code that will allow a user to select a file through a JFileChooser, read each item of the file, outputting each item to the screen, and close the file at the end.

Question 43

If an exception arises in a catch statement, and the exception is of the type caught by the catch statement, then the catch statement catches the same exception. For instance, if the following catch statement first catches an ArithmeticException and, while executing, throws another ArithmeticException, it is able to catch the second ArithmeticException as well the first.
catch (ArithmeticException ex) {...}

Question 44

Explain or provide an example showing how each of the following Exceptions could arise.
a) ArithmeticException
b) NullPointerException
c) NumberFormatException
d) IndexOutOfBoundsException
e) IOException

Question 45

While the Exception class is part of java.lang, IOException is part of java.io.

Question 46

A combo box allows the user to select one of several options from a "drop down" menu.

Question 47

Write code with a try statement and proper catch statements to attempt to take the square root of an int value input using the BufferedReader keyboard. Catch all Exceptions that could possibly be thrown.

Question 48

A combo box generates an item event when the user makes a selection.

Question 49

A JTextArea can be used to display text, but not to edit text by the user.

Question 50

The difference between the throw reserved word and the throws reserved word is that throw is used within a method body, while throws is used within a method header.

Question 51

An image (such as a jpg or gif) can be added a JLabel and JButton but not a JTextArea.

Question 52

Assume that you will want to save, using object serialization, a Student's name, ssn, major and minor to a disk file. Write the instance data definitions for Student.

Question 53

Rewrite the following method using try and catch statements instead of the throws clause in the method's header.
public String getInput(String filename) throws IOException
{
BufferedReader infile = new BufferedReader(new FileReader(filename));
String response = infile.readLine( );
infile.close( );
return response;
}

Question 54

Write a save method that will save a given student to the String filename passed as a parameter.

Question 55

Test scores should fall between 0 and 100. Assume an Exception called TestScoreException has been implemented and imported. Write code to input 10 test scores, compute their average, but throw a TestScoreException in case any inputs violate the proper range. Assume keyboard is a BufferedReader, already instantiated.

Question 56

Rewrite the following code using try and catch statements, catching any exceptions that might be thrown. Assume keyboard is a BufferedReader.
for (j=0;j{
x = Integer.parseInt(keyboard.readLine( ));
y[j] = 1 / x;
}

Question 57

Scroll panes automatically will scroll vertically, but special code needs to be used if a scroll pane is to scroll horizontally.

Question 58

The following defines a new Exception called AnewException.
public Exception ANewException
{
public ANewException(String message)
{
super(message);
}
}

Question 59

Write code that will create a BufferedReader object to input from standard input (System.in) an int, a double and a char.

Question 60

Write a set of code that will allow a user to select a file through a JFileChooser and store all items in the String array list to the selected file, closing the file when done.

Question 61

By now you almost certainly have run a Java program that has experienced a NullPointerException. Explain the reason(s) that a NullPointerException may be generated.

Question 62

Explain how you would use a Timer to create animation in a JLabel.

Question 63

Write a set of code that will create 4 JButtons and add each of these to a JPanel so that they appear in a 2x2 grid. The JButtons will not have any text appear in them (i.e. no commands or names) but instead, will each appear as a color set by the user by using JColorChooser.

Question 64

Write code to display the contents of the String array stuff to a JTextArea where each element of the array is placed on individual lines. Assume that no String is more than 25 characters long.

Question 65

Why might you want to create your own exception class?
What purpose would it serve?

Question 66

Write a set of code that will allow a user to select an input image and then place this image in a JLabel lab1 and add lab1 to a JPanel as the northern component in a JFrame using BorderLayout. The JFrame has already been instantiated as jf and the BorderLayout already established. Hint: a JFileChooser returns a File and JLabel requires the String name of a file as an argument. A File can return its name using File class' method getAbsolutePath( )

Question 67

What is a mnemonic?
What are they used for?

Question 68

What are the three standard I/O streams and what purposes do they fulfill?