Learning Java

Chapter 10. Input/Output Facilities

In this chapter, we’ll continue our exploration of the Java API by looking at many of the classes in the java.io package. Figure 10.1 shows the class hierarchy of the java.io package.

Figure 10-1. The java.io package

We’ll start by looking at the stream classes in java.io; these classes are all subclasses of the basic InputStream, OutputStream, Reader, and Writer classes. Then we’ll examine the File class and discuss how you can interact with the filesystem using classes in java.io. Finally, we’ll take a quick look at the data compression classes provided in java.util.zip.

Streams

All 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 terminal input and output, reading or writing files, or communicating through sockets in Java, you are using a stream of one type or another. So that you can see the forest without being distracted by the trees, we’ll start by summarizing the classes involved with the different types of streams:

InputStream/OutputStream

Abstract classes that define the basic functionality for reading or writing an unstructured sequence of bytes. All other byte streams in Java are built on top of the basic InputStream and OutputStream.

Reader/Writer

Abstract classes that ...