---

Overview Package Class Use Tree Deprecated Index Help		Java™ Platform Standard Ed. 6
PREV CLASS NEXT CLASS	FRAMES NO FRAMES All Classes
SUMMARY: NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

---

java.io
Class Reader

java.lang.Object
 extended by java.io.Reader

All Implemented Interfaces:

Closeable, Readable

Direct Known Subclasses:

BufferedReader, CharArrayReader, FilterReader, InputStreamReader, PipedReader, StringReader

---

public abstract class Reader
extends Object
implements Readable, Closeable

Abstract class for reading character streams. The only methods that a subclass must implement are read(char[], int, int) and close(). Most subclasses, however, will override some of the methods defined here in order to provide higher efficiency, additional functionality, or both.

Since:

JDK1.1

See Also:

BufferedReader, LineNumberReader, CharArrayReader, InputStreamReader, FileReader, FilterReader, PushbackReader, PipedReader, StringReader, Writer

---

Field Summary
protected Object	lock The object used to synchronize operations on this stream.

Constructor Summary
protected	Reader() Creates a new character-stream reader whose critical sections will synchronize on the reader itself.
protected	Reader(Object lock) Creates a new character-stream reader whose critical sections will synchronize on the given object.

Method Summary
abstract 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) Reads characters into an array.
abstract int	read(char[] cbuf, int off, int len) Reads characters into a portion of an array.
int	read(CharBuffer target) Attempts to read characters into the specified character buffer.
boolean	ready() Tells whether this stream is ready to be read.
void	reset() Resets the stream.
long	skip(long n) Skips characters.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

lock

protected Object lock

The object used to synchronize operations on this stream. For efficiency, a character-stream object may use an object other than itself to protect critical sections. A subclass should therefore use the object in this field rather than this or a synchronized method.

Constructor Detail

Reader

protected Reader()

Creates a new character-stream reader whose critical sections will synchronize on the reader itself.

---

Reader

protected Reader(Object lock)

Creates a new character-stream reader whose critical sections will synchronize on the given object.

Parameters:

lock - The Object to synchronize on.

Method Detail

read

public int read(CharBuffer target)
 throws IOException

Attempts to read characters into the specified character buffer. The buffer is used as a repository of characters as-is: the only changes made are the results of a put operation. No flipping or rewinding of the buffer is performed.

Specified by:

read in interface Readable

Parameters:

target - the buffer to read characters into

Returns:

The number of characters added to the buffer, or -1 if this source of characters is at its end

Throws:

IOException - if an I/O error occurs

NullPointerException - if target is null

ReadOnlyBufferException - if target is a read only buffer

Since:

1.5

---

read

public int read()
 throws IOException

Reads a single character. This method will block until a character is available, an I/O error occurs, or the end of the stream is reached.

Subclasses that intend to support efficient single-character input should override this method.

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)
 throws IOException

Reads characters into an array. This method will block until some input is available, an I/O error occurs, or the end of the stream is reached.

Parameters:

cbuf - Destination buffer

Returns:

The number of characters read, or -1 if the end of the stream has been reached

Throws:

IOException - If an I/O error occurs

---

read

public abstract 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.

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:

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.

Parameters:

n - The number of characters to skip

Returns:

The number of characters actually skipped

Throws:

IllegalArgumentException - If n is negative.

IOException - If an I/O error occurs

---

ready

public boolean ready()
 throws IOException

Tells whether this stream is ready to be read.

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. The default implementation always returns false. Subclasses should override this method.

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. Subsequent calls to reset() will attempt to reposition the stream to this point. Not all character-input streams support the mark() operation.

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 the stream does not support mark(), or if some other I/O error occurs

---

reset

public void reset()
 throws IOException

Resets the stream. If the stream has been marked, then attempt to reposition it at the mark. If the stream has not been marked, then attempt to reset it in some way appropriate to the particular stream, for example by repositioning it to its starting point. Not all character-input streams support the reset() operation, and some support reset() without supporting mark().

Throws:

IOException - If the stream has not been marked, or if the mark has been invalidated, or if the stream does not support reset(), or if some other I/O error occurs

---

close

public abstract void close()
 throws IOException

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 Closeable

Throws:

IOException - If an I/O error occurs

---

Overview Package Class Use Tree Deprecated Index Help		Java™ Platform Standard Ed. 6
PREV CLASS NEXT CLASS	FRAMES NO FRAMES All Classes
SUMMARY: NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

---

Submit a bug or feature
For further API reference and developer documentation, see Java SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright © 1993, 2015, Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.

Scripting on this page tracks web page traffic, but does not change the content in any way.