Java I/O

General Techniques for Cross-Platform File Access Code

File manipulation vies with AWT for being the part of Java where it’s hardest to write truly cross-platform, robust code. Until Java 2, Sun really didn’t pay a lot of attention to differences between filesystems on different platforms. The situation is getting better, however. The java.io.File class does work much more reliably across Windows and Unix in Java 2 and has hooks to allow it to work more naturally on other platforms as well. Of course, Java 1.1 is still the primary delivery platform for most Java applications that work with files. To help you achieve greater serenity and overall cross-platform nirvana, I’ve summarized some basic rules from this chapter to help you write file manipulation code that’s robust across a multitude of platforms:

• Never, never, never hardcode pathnames in your application.

• Ask the user to name your files. If you must provide a name for a file, try to make it fit in an 8.3 DOS filename with only pure ASCII characters.

• Do not assume the file separator is “/” (or anything else). Use File.separatorChar instead.

• Do not parse pathnames to find directories. Use the methods of the java.io.File class instead.

• Do not use renameTo() for anything except renaming a file. In particular, do not use it to move a file.

• Try to avoid moving and copying files from within Java programs if at all possible.

• Do not use . to refer to the current directory. Use System.getProperty ("user.dir") instead.

• Do not use .. to refer ...