Reading and Writing |
Character Streams
Reader
andWriter
are the abstract superclasses for character streams injava.io
.Reader
provides the API and partial implementation for readers--streams that read 16-bit characters--andWriter
provides the API and partial implementation for writers--streams that write 16-bit characters.Subclasses of
Reader
andWriter
implement specialized streams and are divided into two categories: those that read from or write to data sinks (shown in gray in the following figures) and those that perform some sort of processing (shown in white). The figure shows the class hierarchies for theReader
andWriter
classes.[PENDING: get two figures from book]
Most programs should use readers and writers to read and write information. This is because they both can handle any character in the Unicode character set (while the byte streams are limited to ISO-Latin-1 8-bit bytes).
Byte Streams
Programs should use the byte streams, descendants ofInputStream
andOutputStream
, to read and write 8-bit bytes.InputStream
andOutputStream
provide the API and some implementation for input streams (streams that read 8-bit bytes) and output streams (streams that write 8-bit bytes). These streams are typically used to read and write binary data such as images and sounds.As with
Reader
andWriter
, subclasses ofInputStream
andOutputStream
provide specialized I/O that falls into two categories: data sink streams and processing streams. Figure 56 shows the class hierarchies for the byte streams.[PENDING: get two figures from book]
As mentioned, two of the byte stream classes,
ObjectInputStream
andObjectOutputStream
, are used for object serialization. These classes are fully covered in Object Serialization.Understanding the I/O Superclasses
Reader
andInputStream
define similar APIs but for different data types. For example,Reader
contains these methods for reading characters and arrays of characters:int read() int read(char cbuf[]) int read(char cbuf[], int offset, int length)InputStream
defines the same methods but for reading bytes and arrays of bytes:Also, bothint read() int read(byte cbuf[]) int read(byte cbuf[], int offset, int length)Reader
andInputStream
provide methods for marking a location in the stream, skipping input, and resetting the current position.
Writer
andOutputStream
are similarly parallel.Writer
defines these methods for writing characters and arrays of characters:Andint write(int c) int write(char cbuf[]) int write(char cbuf[], int offset, int length)OutputStream
defines the same methods but for bytes:All of the streams--readers, writers, input streams, and output streams--are automatically opened when created. You can close any stream explicitly by calling itsint write(int c) int write(byte cbuf[]) int write(byte cbuf[], int offset, int length)close
method. Or the garbage collector can implicitly close it, which occurs when the object is no longer referenced.Learn how to use a selected assortment of these two types of streams in the next two sections:
Reading and Writing |