Class FilterReader

java.lang.Object
java.io.Reader
java.io.FilterReader
All Implemented Interfaces:
Closeable, AutoCloseable, Readable
Direct Known Subclasses:
PushbackReader
public abstract class FilterReader extends Reader
Abstract class for reading filtered character streams. The abstract class FilterReader itself provides default methods that pass all requests to the contained stream. Subclasses of FilterReader should override some of these methods and may also provide additional methods and fields.
Since:
1.1

Field Summary

Modifier and Type Field Description
protected Reader in
The underlying character-input stream.

Fields declared in class java.io.Reader

lock

Constructor Summary

FilterReader(Reader in)
Modifier Constructor Description
protected
Creates a new filtered reader.

Method Summary

Modifier and Type Method Description
void close()
Closes the stream and releases any system resources associated with it.
void mark(int readAheadLimit)
Marks the present position in the stream.
boolean markSupported()
Tells whether this stream supports the mark() operation.
int read()
Reads a single character.
int read(char[] cbuf, int off, int len)
Reads characters into a portion of an array.
boolean ready()
Tells whether this stream is ready to be read.
void reset()
Resets the stream.
long skip(long n)
Skips characters.

Methods declared in class java.io.Reader

nullReader, read, read, transferTo

Methods declared in class java.lang.Object

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

Field Details

in

protected Reader in
The underlying character-input stream.

Constructor Details

FilterReader

protected FilterReader(Reader in)
Creates a new filtered reader.
Parameters:
in - a Reader object providing the underlying stream.
Throws:
NullPointerException - if in is null

Method Details

read

public int read() throws IOException
Reads a single character.
Overrides:
read in class Reader
Returns:
The character read, as an integer in the range 0 to 65535 (0x00-0xffff), or -1 if the end of the stream has been reached
Throws:
IOException - If an I/O error occurs

read

public int read(char[] cbuf, int off, int len) throws IOException
Reads characters into a portion of an array. This method will block until some input is available, an I/O error occurs, or the end of the stream is reached.

If len is zero, then no characters are read and 0 is returned; otherwise, there is an attempt to read at least one character. If no character is available because the stream is at its end, the value -1 is returned; otherwise, at least one character is read and stored into cbuf.

Specified by:
read in class Reader
Parameters:
cbuf - Destination buffer
off - Offset at which to start storing characters
len - Maximum number of characters to read
Returns:
The number of characters read, or -1 if the end of the stream has been reached
Throws:
IndexOutOfBoundsException - If off is negative, or len is negative, or len is greater than cbuf.length - off
IOException - If an I/O error occurs

skip

public long skip(long n) throws IOException
Skips characters. This method will block until some characters are available, an I/O error occurs, or the end of the stream is reached. If the stream is already at its end before this method is invoked, then no characters are skipped and zero is returned.
Overrides:
skip in class Reader
Parameters:
n - The number of characters to skip
Returns:
The number of characters actually skipped
Throws:
IllegalArgumentException - If n is negative and the contained Reader's skip method throws an IllegalArgumentException for a negative parameter
IOException - If an I/O error occurs

ready

public boolean ready() throws IOException
Tells whether this stream is ready to be read.
Overrides:
ready in class Reader
Returns:
True if the next read() is guaranteed not to block for input, false otherwise. Note that returning false does not guarantee that the next read will block.
Throws:
IOException - If an I/O error occurs

markSupported

public boolean markSupported()
Tells whether this stream supports the mark() operation.
Overrides:
markSupported in class Reader
Returns:
true if and only if this stream supports the mark operation.

mark

public void mark(int readAheadLimit) throws IOException
Marks the present position in the stream.
Overrides:
mark in class Reader
Parameters:
readAheadLimit - Limit on the number of characters that may be read while still preserving the mark. After reading this many characters, attempting to reset the stream may fail.
Throws:
IOException - If an I/O error occurs

reset

public void reset() throws IOException
Resets the stream.
Overrides:
reset in class Reader
Throws:
IOException - If an I/O error occurs

close

public void close() throws IOException
Description copied from class: Reader
Closes the stream and releases any system resources associated with it. Once the stream has been closed, further read(), ready(), mark(), reset(), or skip() invocations will throw an IOException. Closing a previously closed stream has no effect.
Specified by:
close in interface AutoCloseable
Specified by:
close in interface Closeable
Specified by:
close in class Reader
Throws:
IOException - If an I/O error occurs

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/io/FilterReader.html