Java IO.pdf - Nguyen Dang Binh

Java I/O
of its own parents, there's potential for infinite recursion. To avoid this possibility, all paths
are converted to canonical paths in the constructor, and these paths are stored in the static
vector seen. A directory is listed only if it has not yet been traversed by this program.
12.3.7.3 The listFiles() methods
The two list() methods return arrays of strings. The strings contain the names of files. You
can use these to construct File objects. Java 2 allows you to eliminate the intermediate step
of creating File objects by providing two listFiles() methods that return arrays of File
objects instead of arrays of strings.
public File[] listFiles() // Java 2
public File[] listFiles(FilenameFilter filter) // Java 2
public File[] listFiles(FileFilter filter) // Java 2
The no-argument variant of listFiles() simply returns an array of all the files in the given
directory. The other two variants return the files that pass through their filters. File and
filename filters will be discussed shortly.
12.3.8 File URLs
File URLs are used inside web browsers to refer to a file on the local hard drive. [3] They have
the basic form:
file:///
should be the fully qualified domain name of the system on which the is
found, though if it's omitted, the local host is assumed. is the hierarchical path to the
file, using a forward slash as a directory separator (regardless of host filename conventions)
and URL encoding of any special characters in filenames that would normally be encoded in a
URL. Examples of file URLs include:
file:///C|/docs/JCE%201.2%20beta%201/guide/API_users_guide.html
file:///usr/local/java/docs/JCE%201.2%20beta%201/guide/API_users_guide.html
file:///D%7C/JAVA/
file:///Macintosh%20HD/Java/Cafe%20%au%20%Lait/course/week4/01.5.html
Many web browsers allow other, nonstandard formats like:
file:///D:/JAVA/
file:///usr/local/java/docs/JCE 1.2 beta 1/guide/API_users_guide.html
file:///C|/jdk2beta4/docs/JCE 1.2 beta 1/guide/API_users_guide.html
file:///C:\jdk1.2beta4\docs\JCE 1.2 beta 1\guide\API_users_guide.html
file:/D:/Java/ioexamples/12/FileDialogApplet.html
Because of the differences between file, and directory names from one computer to the next,
the exact syntax of file URLs is unpredictable from platform to platform and web browser to
web browser. In Java 2 the File class has a toURL() method that returns a file URL that's
appropriate for the local platform:
public URL toURL() throws MalformedURLException // Java 2
3 Very early web browsers used file URLs to refer to FTP sites. However, that usage has mostly disappeared now.
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