Java IO.pdf - Nguyen Dang Binh

Chapter 5
Java I/O
From its first days, Java has always had the network in mind, more so than any other
common programming language. Java is the first programming language to provide as
much support for network I/O as it does for file I/O, perhaps even more. Chapter 5
introduces Java's URL, URLConnection, Socket, and ServerSocket classes, all fertile
sources of streams. Typically the exact type of the stream used by a network
connection is hidden inside the undocumented sun classes. Thus network I/O relies
primarily on the basic InputStream and OutputStream methods. Examples in this
chapter include several simple web and email clients.
Part III: Filter Streams
Chapter 6
Chapter 7
Chapter 8
Chapter 6 introduces filter streams. Filter input streams read data from a preexisting
input stream like a FileInputStream, and have an opportunity to work with or
change the data before it is delivered to the client program. Filter output streams write
data to a preexisting output stream such as a FileOutputStream, and have an
opportunity to work with or change the data before it is written onto the underlying
stream. Multiple filters can be chained onto a single underlying stream to provide the
functionality offered by each filter. Filters streams are used for encryption,
compression, translation, buffering, and much more. At the end of this chapter, the
File Viewer program is redesigned around filter streams to make it more extensible.
Chapter 7 introduces data streams, which are useful for writing strings, integers,
floating-point numbers, and other data that's commonly presented at a level higher
than mere bytes. The DataInputStream and DataOutputStream classes read and
write the primitive Java data types (boolean, int, double, etc.) and strings in a
particular, well-defined, platform-independent format. Since DataInputStream and
DataOutputStream use the same formats, they're complementary. What a data output
stream writes, a data input stream can read, and vice versa. These classes are
especially useful when you need to move data between platforms that may use
different native formats for integers or floating-point numbers. Along the way, you'll
develop classes to read and write little-endian numbers, and you'll extend the File
Viewer program to handle big- and little-endian integers and floating-point numbers of
varying widths.
Chapter 8 shows you how streams can move data from one part of a running Java
program to another. There are three main ways to do this. Sequence input streams
chain several input streams together so that they appear as a single stream. Byte array
streams allow output to be stored in byte arrays and input to be read from byte arrays.
Finally, piped input and output streams allow output from one thread to become input
for another thread.
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