All Implemented Interfaces:

Closeable, AutoCloseable, Readable

Direct Known Subclasses:

BufferedReader, CharArrayReader, FilterReader, InputStreamReader, PipedReader, StringReader

public abstract class Reader
extends Object
implements Readable, Closeable 

Since:

JDK1.1

See Also:

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

• Field Summary

  Fields

  Modifier and Type	Field	Description
  protected Object	lock	The object used to synchronize operations on this stream.

• Constructor Summary

  Constructors

  Modifier	Constructor	Description
  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

  All Methods

  Modifier and Type	Method	Description
  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

    Specified by:

    close in interface AutoCloseable

    Throws:

    IOException - If an I/O error occurs