Streams (Overview)

A stream is a flow of characters to and from a program. The other end of the stream can be anything that can accept or generate a stream of characters, including a console window, a printer, a file on a disk drive, or even another program.

The two basic types of streams in Java are

Character streams: Character streams read and write text characters that represent strings. You can connect a character stream to a text file to store text data on a hard drive. Typically, text files use special characters called delimiters — such as commas or Tabs — to separate elements of the file.

Binary streams: Binary streams read and write individual bytes that represent primitive data types. You can connect a binary stream to a binary file to store binary data on a hard drive. The contents of binary files make perfect sense to the programs that read and write them, but if you try to open a binary file in a text editor, the file’s contents look like gibberish.

Many of the classes described in this part are designed to facilitate stream I/O. For character streams, these classes are

Reader : An abstract class that the other reader classes extend.

FileReader : Provides basic methods for reading data from a character stream that originates from a file. This class reads data one character at a time. You don’t usually work with this class directly. Instead, you use it to connect to a BufferedReader object, which can read the data more efficiently.

BufferedReader : Provides more efficient input from a file-based character stream.

Scanner : Reads characters from a stream and parses it into meaningful data.

Writer : An abstract class that the other writer classes extend.

FileWriter : Connects to a File object and provides basic writing capabilities.

BufferedWriter : Provides more-efficient file-writing capabilities than the basic FileWriter class.

PrintWriter : Writes data to a text file one line at a time. This class typically connects to a FileWriter or BufferedWriter class.

For binary streams, the relevant classes are

InputStream : An abstract class that the other input stream classes extend.

FileInputStream : Connects a binary input stream to a file.

BufferedInputStream : Adds buffering abilities to FileInputStream for more-efficient input.

DataInputStream : Reads primitive data types from a binary input stream.

OutputStream : An abstract class that the other output stream classes extend.

FileOutputStream : Connects a binary output stream to a file.

BufferedOutputStream : Adds buffering to FileOutputStream.

DataOutputStream : Writes primitive data types to a binary output stream.