Java Reference
In-Depth Information
The
File
class includes several overloaded constructors. For example, the
following instance of
File
refers to a file named
myfile.txt
in the current
directory where the JVM is running:
File file
=
new File (
"
myfile.txt
"
);
Again, the file
myfile.txt
may or may not exist in the file system. An attempt
to use a
File
object that refers to a file that does not exist will cause a
FileNot-
FoundException
to be thrown.
The next example creates a
File
object from a file name that includes the
full directory path:
File file = new File ("/tmp/myfile.txt");
Another overloaded constructor allows the separate specification of path and file
name:
File file = new File ("/tmp", "myfile.txt");
File
objects can also represent directories. For example,
File tmp
-
directory
=
new File (
"
/tmp
"
);
There are a number of useful methods in
File
such as the following:
Boolean exist ()
- indicates if the file referred to actually exists
Boolean canWrite ()
- can the file be written to
Boolean canRead ()
- can the file be read
Boolean isFile ()
- does the
File
object represent a file?
Boolean isDirectory ()
-oradirectory?
Given an instance of
File
, the class provides methods to obtain the file name and
path components, to make a directory, to get a listing of the files in a directory,
and so forth:
String getName ()
- get the name of the file (no path included)
String getPath ()
- get the abstract file path
String getCanonicalPath ()
- get the name of the file with path
String getAbsolutePath ()
- get the absolute file path
Java must run on different types of platforms, and file and directory systems differ
among platforms. For example, path names use different separator characters on
different hosts. Windows uses the backslash (“
\
”) and Unix uses the forward slash
(“
/
”). To obtain platform independence, instead of explicit separator characters,
you can use these static constants defined in the
File
class:
File.separator
-
String
with file separator
File.separatorChar
-
char
with file separator
File.pathSeparator
-
String
with path separator
File.pathSeparatorChar
-
char
with path separator
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