Java Quick Reference - java.io Package

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The java.io Package

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The java.io Package - Filters

Filters sit between input and output streams, processing the bytes being transferred
FilterInputStream extends InputStream and FilterOutputStream extends OutputStream
this means a FilterInputStream, and any of it's subclasses, can take any InputStream as an argument and a FilterOutputStream can take any OutputStream
this allows the chaining of filter streams ie a FilterInputStream can take another FilterInputStream; the original source can be an object that is not a filter stream as long as it isn't reading from another input stream
Output filters can also be chained, you can have as many filters as you like but the last in the chain must be an OutpuStream
both methods simply override all their inherited methods, passing all their processing along to the underlying Input or Output stream

FilterInputStream Subclasses
Subclass	Constructors
BufferedInputStream	BufferedInputStream(InputStream in) BufferedInputStream(InputStream in, int size)
DataInputStream	DataInputStream(InputStream in)
LineNumberInputStream	LineNumberInputStream(InputStream in)
PushbackInputStream	PushbackInputStream(InputStream in) PushbackInputStream(InputStream in, int size)

FilterOutputStream Subclasses
Subclass	Constructors
BufferedOutputStream	BufferedOutputStream(OutputStream out) BufferedOutputStream(OutputStream out, int size)
DataOutputStream	DataOutputStream(OutputStream out)
PrintStream	PrintStream(OutputStream out) PrintStream(OutputStream out, boolean autoflush)

technically, you should use PrintWriter when doing character related I/O , PrintStream is included for historical reasons. It should only be used with System.in as it assumes Latin-1 character encoding.
most Reader and Writer classes can also act as filters as most of them already have constructors which take another character stream
to create your own filter streams
1. Create subclasses of FilterInputStream and FilterOutputStream
2. Override the read() and write() methods
3. Override any other methods you might need
4. Make sure the input and output streams work together

	Pkg Overview	Data Streams	Character Streams	Byte Streams	File Class	Readers & Writers
	Filter Streams	Data Input/Output	Reading & Writing Files	Serialization