Chapter 10. File Input and Output

The ability to store data in files and retrieve it later is crucial to desktop and enterprise applications. In this chapter, we’ll look at some of the most popular classes in the and java.nio packages. These packages offer a rich set of tools for basic input and output (I/O) and also provide the framework on which all file and network communication in Java is built. Figure 10-1 shows the breadth of the package.

We’ll 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 data compression and serialization. Along the way, we introduce the java.nio package. The “new” I/O package (or NIO) adds significant functionality tailored for building high-performance services. NIO centers on working with buffers (where you store stuff to make more efficient use of other resources) and channels (where you can efficiently put stuff that can be just as efficiently picked up by others). In some cases, NIO also provides better APIs that can be used in place of some features.1

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Figure 10-1. The class hierarchy


Most I/O in Java is based on streams. Conceptually, a stream represents a flow of data with a writer ...

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