Learning Java, 4th Edition

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 and output, reading or writing files, or communicating through sockets in Java, you are using various types of streams. Later in this chapter, we’ll look at the NIO package, which introduces a similar concept called a channel. One difference betwen the two is that streams are oriented around bytes or characters while channels are oriented around “buffers” containing those data types—yet they perform roughly the same job. Let’s start by summarizing the available 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 define the basic functionality for reading or writing a sequence of character data, with support for Unicode. All other character streams in Java are built on top of Reader and Writer.

InputStreamReader, OutputStreamWriter

Classes that bridge byte and character streams by converting according to a specific character encoding scheme. (Remember: in Unicode, a character is not a byte!)

DataInputStream, DataOutputStream

Specialized stream filters that add the ability to read and write multibyte data types, such as numeric ...