Java IO.pdf - Nguyen Dang Binh

Java I/O
When run, it creates files named mail30446.tem, mail30447.tem, etc. through mail30455.tem.
By default, temporary files are placed in the directory named by the java.io.tmpdir
property. On Unix, this is likely to be /tmp or /var/tmp. On Windows, it's probably C:\temp or
C:\Windows\Temp. On the Mac, it's probably the invisible Temporary Items folder on the
startup drive. You can specify a different directory using the third argument to
createTempFile(). For instance, to create a temporary file in the current working directory:
File cwd = new File(System.getProperty("user.dir"));
File temp = File.createTempFile("rus", ".tmp", cwd);
You often want to delete temporary files when your program exits. You can accomplish this
by passing them to the deleteOnExit() method:
public void deleteOnExit() // Java 2
For example:
File temp = File.createTempFile("mail", ".tem");
temp.deleteOnExit();
This method works on any File object, not just temporary files. Be careful, because there's no
good way to cancel a request to delete files when your program exits.
Temporary files are useful when you need to operate on a file in place. You can do this in two
passes. In the first pass, you read from the file you're converting and write into the temporary
file. In the second pass, you read from the temporary file and write into the file you're
converting. Here's an example:
try {
File infile = new File(args[2]);
File outfile = new File(args[3]);
boolean usingTempFile = false;
if (infile.getCanonicalPath().equals(outfile.getCanonicalPath())) {
outfile = File.createTempFile("temp", null);
outfile.deleteOnExit();
usingTempFile = true;
}
// perform operations as normal, then close both files...
if (usingTempFile) {
FileInputStream fin = new FileInputStream(outfile);
FileOutputStream fout = new FileOutputStream(infile);
StreamCopier.copy(fin, fout);
fin.close();
fout.close();
}
}
catch (IOException e) {System.err.println(e);}
12.3.6 Utility Methods
The File class also contains the usual equals(), hashCode(), and toString() methods,
which behave exactly as you would expect. It does not contain a clone() method.
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