File	Doc	Category	Size	Date	Package
PushbackReader.java	API Doc	Java SE 5 API	7762	Fri Aug 26 14:57:00 BST 2005	java.io

PushbackReader

• java.lang.Object
  • java.io.Reader
    • java.io.FilterReader

Fields Summary
private char[]	buf Pushback buffer
private int	pos Current position in buffer

Constructors Summary
public PushbackReader(Reader in, int size) Create a new pushback reader with a pushback buffer of the given size. param in The reader from which characters will be read param size The size of the pushback buffer exception IllegalArgumentException if size is <= 0 super(in); if (size <= 0) { throw new IllegalArgumentException("size <= 0"); } this.buf = new char[size]; this.pos = size;
public PushbackReader(Reader in) Create a new pushback reader with a one-character pushback buffer. param in The reader from which characters will be read this(in, 1);

Methods Summary
public void	close() Close the stream. exception IOException If an I/O error occurs super.close(); buf = null;
private void	ensureOpen() Check to make sure that the stream has not been closed. if (buf == null) throw new IOException("Stream closed");
public void	mark(int readAheadLimit) Mark the present position in the stream. The mark for class PushbackReader always throws an exception. exception IOException Always, since mark is not supported throw new IOException("mark/reset not supported");
public boolean	markSupported() Tell whether this stream supports the mark() operation, which it does not. return false;
public int	read() Read a single character. return The character read, or -1 if the end of the stream has been reached exception IOException If an I/O error occurs synchronized (lock) { ensureOpen(); if (pos < buf.length) return buf[pos++]; else return super.read(); }
public int	read(char[] cbuf, int off, int len) Read characters into a portion of an array. param cbuf Destination buffer param off Offset at which to start writing 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 synchronized (lock) { ensureOpen(); try { if (len <= 0) { if (len < 0) { throw new IndexOutOfBoundsException(); } else if ((off < 0) || (off > cbuf.length)) { throw new IndexOutOfBoundsException(); } return 0; } int avail = buf.length - pos; if (avail > 0) { if (len < avail) avail = len; System.arraycopy(buf, pos, cbuf, off, avail); pos += avail; off += avail; len -= avail; } if (len > 0) { len = super.read(cbuf, off, len); if (len == -1) { return (avail == 0) ? -1 : avail; } return avail + len; } return avail; } catch (ArrayIndexOutOfBoundsException e) { throw new IndexOutOfBoundsException(); } }
public boolean	ready() Tell whether this stream is ready to be read. exception IOException If an I/O error occurs synchronized (lock) { ensureOpen(); return (pos < buf.length) || super.ready(); }
public void	reset() Reset the stream. The reset method of PushbackReader always throws an exception. exception IOException Always, since reset is not supported throw new IOException("mark/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"); synchronized (lock) { ensureOpen(); int avail = buf.length - pos; if (avail > 0) { if (n <= avail) { pos += n; return n; } else { pos = buf.length; n -= avail; } } return avail + super.skip(n); }
public void	unread(int c) Push back a single character. param c The character to push back exception IOException If the pushback buffer is full, or if some other I/O error occurs synchronized (lock) { ensureOpen(); if (pos == 0) throw new IOException("Pushback buffer overflow"); buf[--pos] = (char) c; }
public void	unread(char[] cbuf, int off, int len) Push back a portion of an array of characters by copying it to the front of the pushback buffer. After this method returns, the next character to be read will have the value cbuf[off], the character after that will have the value cbuf[off+1], and so forth. param cbuf Character array param off Offset of first character to push back param len Number of characters to push back exception IOException If there is insufficient room in the pushback buffer, or if some other I/O error occurs synchronized (lock) { ensureOpen(); if (len > pos) throw new IOException("Pushback buffer overflow"); pos -= len; System.arraycopy(cbuf, off, buf, pos, len); }
public void	unread(char[] cbuf) Push back an array of characters by copying it to the front of the pushback buffer. After this method returns, the next character to be read will have the value cbuf[0], the character after that will have the value cbuf[1], and so forth. param cbuf Character array to push back exception IOException If there is insufficient room in the pushback buffer, or if some other I/O error occurs unread(cbuf, 0, cbuf.length);