de.frame4j.io

Class SwitchedReader

java.lang.Object

java.io.Reader

de.frame4j.io.SwitchedReader

All Implemented Interfaces:

Closeable, AutoCloseable, Readable

@MinDoc(copyright="Copyright  2001 - 2002, 2009  A. Weinert",
        author="Albrecht Weinert",
        version="V.44",
        lastModified="6.05.2021",
        usage="use for unbloody replacement of a Reader chain\'s element",
        purpose="a no-op Reader filter / decorator that can switch its input")
public final class SwitchedReader
extends Reader

A (filter) reader that can switch its input reader.

This Reader just forwards all calls to its associated Reader. In this sense it is just a no-op filter or decorator.
Its special function is its ability to switch the decorated input Reader.
One exemplary use case is the changing of a input chain's character encoding. As the InputStreamReader can't change the encoding it was constructed with, that part of the chain has to be replaced in the process. With SwitchedReader in front of the InputStreamReader no one else is troubled.

Hint: In a certain sense this is a complement to TeeWriter that provides switching in an output chain.

© Copyright 2009 Albrecht Weinert.

See Also:

AppIO, Input

Field Summary

Fields

Modifier and Type	Field and Description
protected Reader	in The Reader to get input from.

Fields inherited from class java.io.Reader

lock

Constructor Summary

Constructors

Constructor and Description
SwitchedReader(Reader in) Make a new SwitchedReader.

Method Summary

Modifier and Type	Method and Description
void	close() Close the associated input reader.
void	mark(int readAheadLimit) Mark the present position in the associated input reader.
boolean	markSupported() Does the associated input reader support the mark() operation.
int	read() Read a single character.
int	read(char[] cbuf, int off, int len) Read some characters into an array.
boolean	ready() Try to tell if the associated input reader is ready.
void	reset() Reset the associated input reader to the last marked position.
long	skip(long n) Skip some characters.
void	switchInput(Reader in, boolean closeOld) Switch the Reader to get input from.

Methods inherited from class java.io.Reader

read, read

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

in

protected volatile Reader in

The Reader to get input from.

Constructor Detail

SwitchedReader

public SwitchedReader(Reader in)

Make a new SwitchedReader.

Parameters:

in - a Reader object providing the underlying input (not null).

Throws:

NullPointerException - if in is null

Method Detail

switchInput

public final void switchInput(Reader in,
                              boolean closeOld)
                       throws IOException

Switch the Reader to get input from.

Parameters:

in - the new Reader to get input from (null or actual has no effect)

closeOld - if true and if switched to in do close the old input

Throws:

IOException - file or stream problems

read

public int read()
         throws IOException

Read a single character.

Overrides:

read in class Reader

Throws:

IOException

read

public int read(char[] cbuf,
                int off,
                int len)
         throws IOException

Read some characters into an array.

Specified by:

read in class Reader

Throws:

IOException

skip

public long skip(long n)
          throws IOException

Skip some characters.

Overrides:

skip in class Reader

Throws:

IOException

ready

public boolean ready()
              throws IOException

Try to tell if the associated input reader is ready.

Overrides:

ready in class Reader

Throws:

IOException

markSupported

public boolean markSupported()

Does the associated input reader support the mark() operation.

Hint: marks and resets just get lost if the associated input reader is switched.

Overrides:

markSupported in class Reader

mark

public void mark(int readAheadLimit)
          throws IOException

Mark the present position in the associated input reader.

Hint: marks and resets just get lost if the associated input reader is switched.

Overrides:

mark in class Reader

Throws:

IOException

reset

public void reset()
           throws IOException

Reset the associated input reader to the last marked position.

Hint: marks and resets just get lost if the associated input reader is switched.

Overrides:

reset in class Reader

Throws:

IOException

close

public void close()
           throws IOException

Close the associated input reader.

Note: by switching to another non null input reader this SwitchedReader would be operable again. This might be an unwanted surprise.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Specified by:

close in class Reader

Throws:

IOException