Java IO.pdf - Nguyen Dang Binh

File f = new File("tmp/");
f.mkdir();
Java I/O
The trailing slash is optional, but it helps you to remember that you're dealing with a directory
rather than a plain file. If the security manager does not allow the directory to be created, a
security exception is thrown. If the directory cannot be created for any other reason, mkdir()
returns false. The mkdir() method only works for single directories. Trying to create a
directory like com/macfaq/io/ with mkdir() only works if com/macfaq already exists.
The mkdirs() method creates every directory in a path that doesn't already exist:
public boolean mkdirs()
For example:
File f = new File("com/macfaq/io/");
f.mkdirs();
mkdirs() returns true if all directories in this path are created or already exist and false if
only some or none of them are created. If mkdirs() returns false, you need to test each
directory in the path to see whether it was created, because the invocation could have been
partially successful.
One reason mkdir() and mkdirs() may return false (fail to create a directory) is that a file
already exists with the name the directory has. Neither mkdir() nor mkdirs() will overwrite
an existing file or directory.
12.3.7.2 Listing directories
The list() method returns an array of strings containing the names of each file in the
directory referred to by the File object:
public String[] list()
This method returns null if the File object doesn't point to a directory. It throws a security
exception if the program isn't allowed to read the directory being listed. An alternative version
of list() uses a FilenameFilter object (discussed later in the chapter) to restrict which
files are included in the list:
public String[] list(FilenameFilter filter)
Example 12.5 is a simple character-mode program that recursively lists all the files in a
directory, and all the files in directories in the directory, and all the files in directories in the
directory, and so on. Files are indented two spaces for each level deep they are in the
hierarchy.
Example 12.5. The DirList Program
import java.io.*;
import java.util.*;
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