java.io

Class Reader

Implemented Interfaces:
AutoCloseable, Closeable, Readable
Known Direct Subclasses:
BufferedReader, CharArrayReader, FilterReader, InputStreamReader, PipedReader, StringReader

public abstract class Reader
extends Object
implements Closeable, Readable

This abstract class forms the base of the hierarchy of classes that read input as a stream of characters. It provides a common set of methods for reading characters from streams. Subclasses implement and extend these methods to read characters from a particular input source such as a file or network connection.

Field Summary

protected Object
lock
This is the Object used for synchronizing critical code sections.

Constructor Summary

Reader()
Unitializes a Reader that will use the object itself for synchronization of critical code sections.
Reader(Object lock)
Initializes a Reader that will use the specified Object for synchronization of critical code sections.

Method Summary

abstract void
close()
Closes the stream.
void
mark(int readLimit)
Marks a position in the input to which the stream can be "reset" by calling the reset() method.
boolean
markSupported()
Returns a boolean that indicates whether the mark/reset methods are supported in this class.
int
read()
Reads an char from the input stream and returns it as an int in the range of 0-65535.
int
read(buf[] )
Reads chars from a stream and stores them into a caller supplied buffer.
abstract int
read(buf[] , int offset, int count)
Read chars from a stream and stores them into a caller supplied buffer.
int
read(CharBuffer buffer)
boolean
ready()
Determines whether or not this stream is ready to be read.
void
reset()
Resets a stream to the point where the mark() method was called.
long
skip(long count)
Skips the specified number of chars in the stream.

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

lock

protected Object lock
This is the Object used for synchronizing critical code sections. Subclasses should use this variable instead of a synchronized method or an explicit synchronization on this

Constructor Details

Reader

protected Reader()
Unitializes a Reader that will use the object itself for synchronization of critical code sections.

Reader

protected Reader(Object lock)
Initializes a Reader that will use the specified Object for synchronization of critical code sections.
Parameters:
lock - The Object to use for synchronization

Method Details

close

public abstract void close()
            throws IOException
Closes the stream. Any futher attempts to read from the stream may generate an IOException.
Specified by:
close in interface Closeable
close in interface AutoCloseable
Throws:
IOException - If an error occurs

mark

public void mark(int readLimit)
            throws IOException
Marks a position in the input to which the stream can be "reset" by calling the reset() method. The parameter readlimit is the number of chars that can be read from the stream after setting the mark before the mark becomes invalid. For example, if mark() is called with a read limit of 10, then when 11 chars of data are read from the stream before the reset() method is called, then the mark is invalid and the stream object instance is not required to remember the mark.
Parameters:
readLimit - The number of chars that can be read before the mark becomes invalid
Throws:
IOException - If an error occurs such as mark not being supported for this class

markSupported

public boolean markSupported()
Returns a boolean that indicates whether the mark/reset methods are supported in this class. Those methods can be used to remember a specific point in the stream and reset the stream to that point.

This method always returns false in this class, but subclasses can override this method to return true if they support mark/reset functionality.

Returns:
true if mark/reset functionality is supported, false otherwise

read

public int read()
            throws IOException
Reads an char from the input stream and returns it as an int in the range of 0-65535. This method also will return -1 if the end of the stream has been reached.

This method will block until the char can be read.

Returns:
The char read or -1 if end of stream
Throws:
IOException - If an error occurs

read

public int read(buf[] )
            throws IOException
Reads chars from a stream and stores them into a caller supplied buffer. This method attempts to completely fill the buffer, but can return before doing so. The actual number of chars read is returned as an int. A -1 is returned to indicate the end of the stream.

This method will block until some data can be read.

This method operates by calling an overloaded read method like so: read(buf, 0, buf.length)

Parameters:
Returns:
The number of chars read or -1 if end of stream.
Throws:
IOException - If an error occurs.

read

public abstract int read(buf[] ,
                         int offset,
                         int count)
            throws IOException
Read chars from a stream and stores them into a caller supplied buffer. It starts storing the data at index offset into the buffer and attempts to read len chars. This method can return before reading the number of chars requested. The actual number of chars read is returned as an int. A -1 is returned to indicate the end of the stream.

This method will block until some data can be read.

This method operates by calling the single char read() method in a loop until the desired number of chars are read. The read loop stops short if the end of the stream is encountered or if an IOException is encountered on any read operation except the first. If the first attempt to read a chars fails, the IOException is allowed to propagate upward. And subsequent IOException is caught and treated identically to an end of stream condition. Subclasses can (and should if possible) override this method to provide a more efficient implementation.

Parameters:
offset - The offset into the array to start storing chars
count - The requested number of chars to read
Returns:
The actual number of chars read, or -1 if end of stream.
Throws:
IOException - If an error occurs.

read

public int read(CharBuffer buffer)
            throws IOException
Specified by:
read in interface Readable
Since:
1.5

ready

public boolean ready()
            throws IOException
Determines whether or not this stream is ready to be read. If it returns false the stream may block if a read is attempted, but it is not guaranteed to do so.

This method always returns false in this class

Returns:
true if the stream is ready to be read, false otherwise.
Throws:
IOException - If an error occurs

reset

public void reset()
            throws IOException
Resets a stream to the point where the mark() method was called. Any chars that were read after the mark point was set will be re-read during subsequent reads.

This method always throws an IOException in this class, but subclasses can override this method if they provide mark/reset functionality.

Throws:
IOException - Always thrown for this class

skip

public long skip(long count)
            throws IOException
Skips the specified number of chars in the stream. It returns the actual number of chars skipped, which may be less than the requested amount.

This method reads and discards chars into a 256 char array until the specified number of chars were skipped or until either the end of stream is reached or a read attempt returns a short count. Subclasses can override this method to provide a more efficient implementation where one exists.

Parameters:
count - The requested number of chars to skip
Returns:
The actual number of chars skipped.
Throws:
IOException - If an error occurs

Reader.java -- base class of classes that read input as a stream of chars Copyright (C) 1998, 1999, 2000, 2003, 2004, 2005 Free Software Foundation This file is part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GNU Classpath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; see the file COPYING. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.