Java Reference
In-Depth Information
Answers to Self-Test Exercises
1.
With an input stream, data flows from a file or input device to your program.
With an output stream, data flows from your program to a file or output device.
2.
A binary file contains data that is processed as binary data. A text file allows your
program and editor to view the file as if it contained a sequence of characters. A
text file can be viewed with an editor, whereas a binary file cannot.
3.
A
FileNotFoundException
would be thrown if the file cannot be opened
because, for example, there is already a directory (folder) named
stuff.txt
.
Note that if the file does not exist but can be created, then no exception
is thrown. If you answered
IOException
, you are not wrong, because a
FileNotFoundException
is an
IOException
. However, the better answer is
the more specific exception class, namely
FileNotFoundException
.
4.
No. That is why we use an object of the class
FileOutputStream
as an argument.
The correct way to
express
the code displayed in the question is as follows:
PrintWriter outputStream =
new
PrintWriter(
new
FileOutputStream("stuff.txt"));
5.
PrintWriter outputStream =
new
PrintWriter(
new
FileOutputStream("sam");
6.
PrintWriter outStream =
new
PrintWriter(
new
FileOutputStream("sam",
true
));
7. Yes, it will send suitable output to the text file because the class
Person
has a
well-defined
toString()
method.
8.
Scanner fileIn =
new
Scanner(
new
FileInputStream("sally"));
9. It throws a
NoSuchElementException
if there are no more tokens. It throws an
InputMismatchException
if the next token is not a well-formed string representation
of an
int
. It throws an
IllegalStateException
if the
Scanner
stream is closed.
10. No. Reading may have reached the end of the file, but another possibility is that
the next token may not be a well-formed string representation of an
int
value.
11. The
FileInputStream
constructor, and thus the
Scanner
constructor invocation,
can throw a
FileNotFoundException
, and this exception needs to be caught or
declared in a
throws
clause.
12.
BufferedReader fileIn =
new
BufferedReader(
new
FileReader("joe"));
13.
The method
readLine
returns a value of type
String
. The method
read
reads a
single
character
, but it returns it as a value of type
int
. To get the value to be of
type
char
, you need to do a type cast.
