Chapter 12. Input/Output Facilities

In this chapter, we continue our exploration of the Java API by looking at many of the classes in the and java.nio packages. These packages offer a rich set of tools for basic I/O and also provide the framework on which all file and network communication in Java is built.

Figure 12-1 shows the class hierarchy of these packages.

We start by looking at the stream classes in, which are subclasses of the basic InputStream, OutputStream, Reader, and Writer classes. Then we’ll examine the File class and discuss how you can read and write files using classes in We also take a quick look at the data compression classes provided in Finally, we begin our investigation of the java.nio package. The NIO, or “new” I/O, package (introduced in Java 1.4) adds significant new functionality for building high-performance services.


Most fundamental I/O in Java is based on streams . A stream represents a flow of data, or a channel of communication with (at least conceptually) a writer at one end and a reader at the other. When you are working with the package to perform terminal input and output, reading or writing files, or communicating through sockets in Java, you are using various types of streams. Later in this chapter, we look at the NIO package, which introduces a similar concept called a channel. But for now, let’s summarize the available types of streams:


Abstract classes ...

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