File	Doc	Category	Size	Date	Package
Reader.java	API Doc	Java SE 5 API	8199	Fri Aug 26 14:57:00 BST 2005	java.io

Reader

• java.lang.Object

Fields Summary
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.
private static final int	maxSkipBufferSize Maximum skip-buffer size
private char[]	skipBuffer Skip buffer, null until allocated

Constructors Summary
protected Reader() Create a new character-stream reader whose critical sections will synchronize on the reader itself. this.lock = this;
protected Reader(Object lock) Create a new character-stream reader whose critical sections will synchronize on the given object. param lock The Object to synchronize on. if (lock == null) { throw new NullPointerException(); } this.lock = lock;

Methods Summary
public abstract void	close() Close the stream. Once a stream has been closed, further read(), ready(), mark(), or reset() invocations will throw an IOException. Closing a previously-closed stream, however, has no effect. exception IOException If an I/O error occurs
public void	mark(int readAheadLimit) Mark 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. param 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. exception IOException If the stream does not support mark(), or if some other I/O error occurs throw new IOException("mark() not supported");
public boolean	markSupported() Tell whether this stream supports the mark() operation. The default implementation always returns false. Subclasses should override this method. return true if and only if this stream supports the mark operation. return false;
public int	read(java.nio.CharBuffer target) 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. param target the buffer to read characters into return 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 throws NullPointerException if target is null throws ReadOnlyBufferException if target is a read only buffer int len = target.remaining(); char[] cbuf = new char[len]; int n = read(cbuf, 0, len); if (n > 0) target.put(cbuf, 0, n); return n;
public int	read() Read 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. return 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 exception IOException If an I/O error occurs char cb[] = new char[1]; if (read(cb, 0, 1) == -1) return -1; else return cb[0];
public int	read(char[] cbuf) Read 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. param cbuf Destination buffer return The number of characters read, or -1 if the end of the stream has been reached exception IOException If an I/O error occurs return read(cbuf, 0, cbuf.length);
public abstract int	read(char[] cbuf, int off, int len) Read 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. param cbuf Destination buffer param off Offset at which to start storing characters param len Maximum number of characters to read return The number of characters read, or -1 if the end of the stream has been reached exception IOException If an I/O error occurs
public boolean	ready() Tell whether this stream is ready to be read. return 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. exception IOException If an I/O error occurs return false;
public void	reset() Reset 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(). exception 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 throw new IOException("reset() not supported");
public long	skip(long n) Skip characters. This method will block until some characters are available, an I/O error occurs, or the end of the stream is reached. param n The number of characters to skip return The number of characters actually skipped exception IllegalArgumentException If n is negative. exception IOException If an I/O error occurs if (n < 0L) throw new IllegalArgumentException("skip value is negative"); int nn = (int) Math.min(n, maxSkipBufferSize); synchronized (lock) { if ((skipBuffer == null) || (skipBuffer.length < nn)) skipBuffer = new char[nn]; long r = n; while (r > 0) { int nc = read(skipBuffer, 0, (int)Math.min(r, nn)); if (nc == -1) break; r -= nc; } return n - r; }