Learning Java, 5th Edition

Chapter 11. Networking and I/O

In this chapter, we continue our exploration of the Java API by looking at many of the classes in the java.io and java.nio packages. These packages offer a rich set of tools for basic I/O (input/output) and also provide the framework on which all file and network communication in Java is built. Figure 11-1 shows the class hierarchy of these packages. We’ll only cover a selection of this hierarchy, but you can see that it is quite broad. Once you have a handle on local file I/O, we’ll add the java.net package and look at some basic networking concepts. (We’ll tackle the most popular of networking environments—the web—in Chapter 12.)

We’ll start by looking at the stream classes in java.io, 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 java.io. We also take a quick look at data compression and serialization. Along the way, we’ll also introduce the java.nio package. The NIO package (or “new” I/O) adds significant functionality tailored for building high-performance services and in some cases simply provides newer, better APIs that can be used in place of some java.io features.¹

Streams

Most fundamental I/O in Java is based on streams. A stream represents a flow of data with (at least conceptually) a writer at one end and a reader at the other. When you are working with the java.io package to perform terminal input ...