Deck 11: Exceptions

Question 1

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

Answer 1

D
Explanation: D) A thrown exception is either caught by the current code if the code is contained inside a try statement and the appropriate catch statement is implemented, or else it is propagated to the method that invoked the method that caused the exception and caught there in an appropriate catch statement, or else it continues to be propagated through the methods in the opposite order that those methods were invoked. This process stops however once the main method is reached. If not caught there, the exception causes termination of the program (this would be answer a, the exception was ignored). However, an exception is not thrown to an Exception class.

Question 2

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 2

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 3

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

Answer 3

B
Explanation: B) The StringIndexOutOfBoundsException is thrown if a parameter of a String method references a position in the String that is beyond the bounds of the String (i.e. a negative int or an int greater than or equal to the number of characters in the String). This can occur in either charAt or substring methods.

Question 4

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 5

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 6

NullPointerException and ArithmeticException are both derived from which class?

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

Question 7

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 8

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 9

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 10

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 11

Character streams manage

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

Question 12

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 13

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 14

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 15

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 16

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

Question 17

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 18

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 19

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 20

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

Question 21

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 22

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 23

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

Question 24

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 25

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 26

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

Question 27

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 28

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 29

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 30

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 31

A Timer object generates ________ at regular intervals.

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

Question 32

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 33

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 34

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

Question 35

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 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 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 38

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 39

The showDialog method is part of which class?

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

Question 40

All run-time Errors throw Exceptions.

Question 41

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 42

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

Question 43

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 44

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 45

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 46

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

Question 47

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 48

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

Question 49

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 50

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

Question 51

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

Question 52

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 53

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

Question 54

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 55

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

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

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 58

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

Question 59

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

Question 60

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

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

What is a mnemonic?
What are they used for?

Question 63

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

Question 64

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 65

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

Question 66

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

Question 67

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 68

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.