Java I/O

Chapter 12. Working with Files

You’ve already learned how to read and write data in files using file input streams and file output streams. That’s not all there is to files. Files can be created, moved, renamed, copied, deleted, and otherwise manipulated without respect to their contents. Files are also often associated with meta-information that’s not strictly part of the contents of the file, such as the time the file was created, the icon for the file, the permissions that determine which users can read or write to the file, and even the name of the file.

While the abstraction of the contents of a file as an ordered sequence of bytes used by file input and output streams is almost standard across platforms, the meta-information is not. The java.io.File class attempts to provide a platform-independent abstraction for common file operations and meta-information. Unfortunately, this class really shows its Unix roots. It works well on Unix, adequately on Windows and OS/2—with a few caveats—and fails miserably on the Macintosh. Java 2 improves things, but there’s still a lot of history—and coming up with something that genuinely works on all platforms is an extremely difficult problem.

File manipulation is thus one of the real difficulties of cross-platform Java programming. Before you can hope to write truly cross-platform code, you need a solid understanding of the filesystem basics on all the target platforms. This chapter tries to cover those basics for the major platforms that ...