Java Reference
In-Depth Information
K.3
The
java.io
and
java.nio.file
packages
The
java.io
and
java.nio.file
packages contain classes that support input and output
and access to the file system. Many of the input/output classes in
java.io
are distinguished
by whether they are
stream-based
(operating on binary data) or
readers
and
writers (
operating
on characters). The
java.nio.file
package supplies several classes that support convenient
access to the file system.
package java.io.file-Summary of the most important classes and interfaces
interface
Serializable
The
Serializable
interface is an empty interface requiring no code to be
written in an implementing class. Classes implement this interface in order to
be able to participate in the serialization process.
Serializable
objects
may be written and read as a whole to and from sources of output and input.
This makes storage and retrieval of persistent data a relatively simple pro-
cess in Java. See the
ObjectInputStream
and
ObjectOutputStream
classes for further information.
class
BufferedReader
BufferedReader
is a class that provides buffered character-based access
to a source of input. Buffered input is often more efficient than unbuffered,
particularly if the source of input is in the external file system. Because it buff-
ers input, it is able to offer a
readLine
method that is not available in most
other input classes. Key methods are
close
,
read
, and
readLine
.
class
BufferedWriter
BufferedWriter
is a class that provides buffered character-based output.
Buffered output is often more efficient than unbuffered, particularly if the des-
tination of the output is in the external file system. Key methods are
close
,
flush
, and
write
.
class
File
The
File
class provides an object representation for files and folders (directo-
ries) in an external file system. Methods exist to indicate whether a file is read-
able and/or writeable, and whether it is a file or a folder. A
File
object can be
created for a nonexistent file, which may be a first step in creating a physical
file on the file system. Key methods are
canRead
,
canWrite
,
createNew-
File
,
createTempFile
,
getName
,
getParent
,
getPath
,
isDirec-
tory
,
isFile
, and
listFiles
.
class
FileReader
The
FileReader
class is used to open an external file ready for reading its
contents as characters. A
FileReader
object is often passed to the con-
structor of another reader class (such as a
BufferedReader
) rather than
being used directly. Key methods are
close
and
read
.
class
FileWriter
The
FileWriter
class is used to open an external file ready for writing
character-based data. Pairs of constructors determine whether an existing
file will be appended or its existing contents discarded. A
FileWriter
ob-
ject is often passed to the constructor of another
Writer
class (such as a
BufferedWriter
) rather than being used directly. Key methods are
close
,
flush
, and
write
.
class
IOException
IOException
is a checked exception class that is at the root of the excep-
tion hierarchy of most input/output exceptions.
interface
Path
The
Path
interface provides the key methods for accessing information about
a file in the file system.
Path
is, in effect, a replacement for the older
File
class of the
java.io
package.
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