This chapter is largely devoted to one class:
class gives you the ability to list directories, obtain file status,
rename and delete files on disk, create directories, and perform
other filesystem operations. Many of these would be considered
“system programming” functions on some operating systems.
Java makes them all as portable as possible.
Note that many of the methods of this class attempt to modify the
permanent file store, or disk filesystem, of the computer you run
them on. Naturally, you might not have permission to change certain
files in certain ways. This can be detected by the Java Virtual
Machine’s (or the browser’s, in an applet)
SecurityManager, which will throw an instance of
the unchecked exception
failure can also be detected by the underlying operating system: if
the security manager approves it but the user running your program
lacks permissions on the directory, for example, then you will either
get back an indication (such as false), or an instance of the checked
IOException. This must be caught (or
declared in the
throws clause) in any code that
calls any method that tries to change the filesystem.