Java Reference
In-Depth Information
•A
SequenceInputStream
concatenates several
InputStream
s. When the program reaches the end
of an input stream, that stream closes, and the next stream in the sequence opens.
•The
Reader
(p. 675) and
Writer
(p. 675)
abstract
classes are Unicode character-based streams.
Most byte-based streams have corresponding character-based concrete
Reader
or
Writer
classes.
• Classes
BufferedReader
(p. 675) and
BufferedWriter
(p. 675) buffer character-based streams.
• Classes
CharArrayReader
(p. 676) and
CharArrayWriter
(p. 676) manipulate
char
arrays.
•A
LineNumberReader
(p. 676) is a buffered character stream that tracks the number of lines read.
• Classes
FileReader
(p. 676) and
FileWriter
(p. 676) perform character-based file I/O.
• Class
PipedReader
(p. 676) and class
PipedWriter
(p. 676) implement piped-character streams
for transferring data between threads.
• Class
StringReader
(p. 676) and
StringWriter
(p. 676) read characters from and write charac-
ters to
String
s, respectively. A
PrintWriter
(p. 654) writes characters to a stream.
Self-Review Exercises
15.1
Determine whether each of the following statements is
true
or
false
. If
false
, explain why.
a) You must explicitly create the stream objects
System.in
,
System.out
and
System.err
.
b) When reading data from a file using class
Scanner
, if you wish to read data in the file mul-
tiple times, the file must be closed and reopened to read from the beginning of the file.
c)
Files
static
method
exists
receives a
Path
and determines whether it exists (either as
a file or as a directory) on disk
d)
Binary files are human readable in a text editor.
e)
An absolute path contains all the directories, starting with the root directory, that lead
to a specific file or directory.
f)
Class
Formatter
contains method
printf
, which enables formatted data to be output
to the screen or to a file.
15.2
Complete the following tasks, assuming that each applies to the same program:
a)
Write a statement that opens file
"oldmast.txt"
for input—use
Scanner
variable
in-
OldMaster
.
b)
Write a statement that opens file
"trans.txt"
for input—use
Scanner
variable
in-
Transaction
.
c)
Write a statement that opens file
"newmast.txt"
for output (and creation)—use
for-
matter
variable
outNewMaster
.
d)
Write the statements needed to read a record from the file
"oldmast.txt"
. Use the data
to create an object of class
Account
—use
Scanner
variable
inOldMaster
. Assume that
class
Account
is the same as the
Account
class in Fig. 15.9.
e)
Write the statements needed to read a record from the file
"trans.txt"
. The record is
an object of class
TransactionRecord
—use
Scanner
variable
inTransaction
. Assume
that class
TransactionRecord
contains method
setAccount
(which takes an
int
) to set
the account number and method
setAmount
(which takes a
double
) to set the amount
of the transaction.
f)
Write a statement that outputs a record to the file
"newmast.txt"
. The record is an ob-
ject of type
Account
—use
Formatter
variable
outNewMaster
.
15.3
Complete the following tasks, assuming that each applies to the same program:
a)
Write a statement that opens file
"oldmast.ser"
for input—use
ObjectInputStream
variable
inOldMaster
to wrap an
InputStream
object.
b)
Write a statement that opens file
"trans.ser"
for input—use
ObjectInputStream
vari-
able
inTransaction
to wrap an
InputStream
object.
