Learning Java, 4th Edition

The NIO File API

We are now going to turn our attention from the original, “classic” Java File API to the new, NIO, File API introduced with Java 7. As we mentioned earlier, the NIO File API can be thought of as either a replacement for or a complement to the classic API. Included in the NIO package, the new API is nominally part of an effort to move Java toward a higher performance and more flexible style of I/O supporting selectable and asynchronously interruptable channels. However, in the context of working with files, the new API’s strength is that it provides a fuller abstraction of the filesystem in Java.

In addition to better support for existing, real world, filesystem types—including for the first time the ability to copy and move files, manage links, and get detailed file attributes like owners and permissions—the new File API allows entirely new types of filesystems to be implemented directly in Java. The best example of this is the new ZIP filesystem provider that makes it possible to “mount” a ZIP archive file as a filesystem and work with the files within it directly using the standard APIs, just like any other filesystem. Additionally, the NIO File package provides some utilities that would have saved Java developers a lot of repeated code over the years, including directory tree change monitoring, filesystem traversal (a visitor pattern), filename “globbing,” and convenience methods to read entire files directly into memory.

We’ll cover the basic File API in this ...