Learning Java, 4th Edition

File I/O

In this chapter, we’re going to talk about the Java file I/O API. To be more precise, we are going to talk about two file APIs: first, there is the core java.io File I/O facility that has been part of Java since the beginning. Then there is the “new” java.nio.file API introduced in Java 7. In general the NIO packages, which we’ll cover in detail later and which touch upon not only files but all types of network and channel I/O, were introduced to add advanced features that make Java more scaleable and higher performance. However, in the case of file NIO, the new package is also just somewhat of a “do-over” on the original API. In movie terms, you can think of the two APIs as the “classic” and the “reboot” of the series. The new API completely duplicates the functionality of the original, but because the core API is so fundamental (and in some cases simpler), it is likely that many people will prefer to keep using it. We’ll start with the classic API centering on java.io.File and later we’ll cover the new API, which centers on the analogous java.nio.Path.

Working with files in Java is easy, but poses some conceptual problems. Real-world filesystems can vary widely in architecture and implementation: think of the differences between Mac, PC, and Unix systems when it comes to filenames. Java tries to mask some of these differences and provide information to help an application tailor itself to the local environment, but it leaves a lot of the details of file access implementation ...