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You attach a filtered stream to another stream to filter the data as it's read from or written to the original stream. Thejava.io
package contains these filtered streams which are subclasses of eitherFilterInputStream
or
FilterOutputStream
:
This section shows you how to use filtered streams through an example that uses a
DataInputStream
andDataOutputStream
BufferedInputStream
andBufferedOutputStream
LineNumberInputStream
PushbackInputStream
PrintStream
(this is an output stream)DataInputStream
and aDataOutputStream
. In addition, this section shows you how to write your own filtered streams.
[PENDING: readLine has been deprecated. UPdate this section as per book, and book in new psuedo-code here]To use a filtered input or output stream, attach the filtered stream to another input or output stream. For example, you can attach a
DataInputStream
to the standard input stream as in the following code:You might do this so that you can use the more convenientDataInputStream dis = new DataInputStream(System.in); String input; while ((input = dis.readLine()) != null) { . . . // do something interesting here }readXXX
methods, such asreadLine
, implemented byDataInputStream
.
This page provides and explains an example of usingDataInputStream
andDataOutputStream
, two filtered streams that can read and write primitive Java data types.
Many programmers find that they need to implement their own streams that filter or process data as it is being written to or read from the stream. Sometimes the processing is independent of the format of the data, such as counting various items in the stream, and sometimes the processing is directly related to the data itself or the format of the data, such as reading and writing data that is contained in rows and columns. Often, these programmers subclassFilterOutputStream
andFilterInputStream
to achieve their goals. This section describes an example of how to subclassFileInputStream
andFilterOutputStream
to create your own filtered streams.
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