File	Doc	Category	Size	Date	Package
BufferedReader.java	API Doc	Java SE 6 API	14593	Tue Jun 10 00:25:32 BST 2008	java.io

BufferedReader

• java.lang.Object
  • java.io.Reader

BufferedReader in
= new BufferedReader(new FileReader("foo.in"));

Fields Summary
private Reader	in
private char[]	cb
private int	nChars
private int	nextChar
private static final int	INVALIDATED
private static final int	UNMARKED
private int	markedChar
private int	readAheadLimit
private boolean	skipLF If the next character is a line feed, skip it
private boolean	markedSkipLF The skipLF flag when the mark was set
private static int	defaultCharBufferSize
private static int	defaultExpectedLineLength

Constructors Summary
public BufferedReader(Reader in, int sz) Creates a buffering character-input stream that uses an input buffer of the specified size. param in A Reader param sz Input-buffer size exception IllegalArgumentException If sz is <= 0 super(in); if (sz <= 0) throw new IllegalArgumentException("Buffer size <= 0"); this.in = in; cb = new char[sz]; nextChar = nChars = 0;
public BufferedReader(Reader in) Creates a buffering character-input stream that uses a default-sized input buffer. param in A Reader this(in, defaultCharBufferSize);

Methods Summary
public void	close() synchronized (lock) { if (in == null) return; in.close(); in = null; cb = null; }
private void	ensureOpen() Checks to make sure that the stream has not been closed if (in == null) throw new IOException("Stream closed");
private void	fill() Fills the input buffer, taking the mark into account if it is valid. int dst; if (markedChar <= UNMARKED) { /* No mark */ dst = 0; } else { /* Marked */ int delta = nextChar - markedChar; if (delta >= readAheadLimit) { /* Gone past read-ahead limit: Invalidate mark */ markedChar = INVALIDATED; readAheadLimit = 0; dst = 0; } else { if (readAheadLimit <= cb.length) { /* Shuffle in the current buffer */ System.arraycopy(cb, markedChar, cb, 0, delta); markedChar = 0; dst = delta; } else { /* Reallocate buffer to accommodate read-ahead limit */ char ncb[] = new char[readAheadLimit]; System.arraycopy(cb, markedChar, ncb, 0, delta); cb = ncb; markedChar = 0; dst = delta; } nextChar = nChars = delta; } } int n; do { n = in.read(cb, dst, cb.length - dst); } while (n == 0); if (n > 0) { nChars = dst + n; nextChar = dst; }
public void	mark(int readAheadLimit) Marks the present position in the stream. Subsequent calls to reset() will attempt to reposition the stream to this point. param readAheadLimit Limit on the number of characters that may be read while still preserving the mark. An attempt to reset the stream after reading characters up to this limit or beyond may fail. A limit value larger than the size of the input buffer will cause a new buffer to be allocated whose size is no smaller than limit. Therefore large values should be used with care. exception IllegalArgumentException If readAheadLimit is < 0 exception IOException If an I/O error occurs if (readAheadLimit < 0) { throw new IllegalArgumentException("Read-ahead limit < 0"); } synchronized (lock) { ensureOpen(); this.readAheadLimit = readAheadLimit; markedChar = nextChar; markedSkipLF = skipLF; }
public boolean	markSupported() Tells whether this stream supports the mark() operation, which it does. return true;
public int	read() Reads a single character. 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 synchronized (lock) { ensureOpen(); for (;;) { if (nextChar >= nChars) { fill(); if (nextChar >= nChars) return -1; } if (skipLF) { skipLF = false; if (cb[nextChar] == '\n") { nextChar++; continue; } } return cb[nextChar++]; } }
public int	read(char[] cbuf, int off, int len) Reads characters into a portion of an array. This method implements the general contract of the corresponding {@link Reader#read(char[], int, int) read} method of the {@link Reader} class. As an additional convenience, it attempts to read as many characters as possible by repeatedly invoking the read method of the underlying stream. This iterated read continues until one of the following conditions becomes true: The specified number of characters have been read, The read method of the underlying stream returns -1, indicating end-of-file, or The ready method of the underlying stream returns false, indicating that further input requests would block. If the first read on the underlying stream returns -1 to indicate end-of-file then this method returns -1. Otherwise this method returns the number of characters actually read. Subclasses of this class are encouraged, but not required, to attempt to read as many characters as possible in the same fashion. Ordinarily this method takes characters from this stream's character buffer, filling it from the underlying stream as necessary. If, however, the buffer is empty, the mark is not valid, and the requested length is at least as large as the buffer, then this method will read characters directly from the underlying stream into the given array. Thus redundant BufferedReaders will not copy data unnecessarily. 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 synchronized (lock) { ensureOpen(); if ((off < 0) || (off > cbuf.length) || (len < 0) || ((off + len) > cbuf.length) || ((off + len) < 0)) { throw new IndexOutOfBoundsException(); } else if (len == 0) { return 0; } int n = read1(cbuf, off, len); if (n <= 0) return n; while ((n < len) && in.ready()) { int n1 = read1(cbuf, off + n, len - n); if (n1 <= 0) break; n += n1; } return n; }
private int	read1(char[] cbuf, int off, int len) Reads characters into a portion of an array, reading from the underlying stream if necessary. if (nextChar >= nChars) { /* If the requested length is at least as large as the buffer, and if there is no mark/reset activity, and if line feeds are not being skipped, do not bother to copy the characters into the local buffer. In this way buffered streams will cascade harmlessly. */ if (len >= cb.length && markedChar <= UNMARKED && !skipLF) { return in.read(cbuf, off, len); } fill(); } if (nextChar >= nChars) return -1; if (skipLF) { skipLF = false; if (cb[nextChar] == '\n") { nextChar++; if (nextChar >= nChars) fill(); if (nextChar >= nChars) return -1; } } int n = Math.min(len, nChars - nextChar); System.arraycopy(cb, nextChar, cbuf, off, n); nextChar += n; return n;
java.lang.String	readLine(boolean ignoreLF) Reads a line of text. A line is considered to be terminated by any one of a line feed ('\n'), a carriage return ('\r'), or a carriage return followed immediately by a linefeed. param ignoreLF If true, the next '\n' will be skipped return A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached see java.io.LineNumberReader#readLine() exception IOException If an I/O error occurs StringBuffer s = null; int startChar; synchronized (lock) { ensureOpen(); boolean omitLF = ignoreLF || skipLF; bufferLoop: for (;;) { if (nextChar >= nChars) fill(); if (nextChar >= nChars) { /* EOF */ if (s != null && s.length() > 0) return s.toString(); else return null; } boolean eol = false; char c = 0; int i; /* Skip a leftover '\n', if necessary */ if (omitLF && (cb[nextChar] == '\n")) nextChar++; skipLF = false; omitLF = false; charLoop: for (i = nextChar; i < nChars; i++) { c = cb[i]; if ((c == '\n") || (c == '\r")) { eol = true; break charLoop; } } startChar = nextChar; nextChar = i; if (eol) { String str; if (s == null) { str = new String(cb, startChar, i - startChar); } else { s.append(cb, startChar, i - startChar); str = s.toString(); } nextChar++; if (c == '\r") { skipLF = true; } return str; } if (s == null) s = new StringBuffer(defaultExpectedLineLength); s.append(cb, startChar, i - startChar); } }
public java.lang.String	readLine() Reads a line of text. A line is considered to be terminated by any one of a line feed ('\n'), a carriage return ('\r'), or a carriage return followed immediately by a linefeed. return A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached exception IOException If an I/O error occurs return readLine(false);
public boolean	ready() Tells whether this stream is ready to be read. A buffered character stream is ready if the buffer is not empty, or if the underlying character stream is ready. exception IOException If an I/O error occurs synchronized (lock) { ensureOpen(); /* * If newline needs to be skipped and the next char to be read * is a newline character, then just skip it right away. */ if (skipLF) { /* Note that in.ready() will return true if and only if the next * read on the stream will not block. */ if (nextChar >= nChars && in.ready()) { fill(); } if (nextChar < nChars) { if (cb[nextChar] == '\n") nextChar++; skipLF = false; } } return (nextChar < nChars) || in.ready(); }
public void	reset() Resets the stream to the most recent mark. exception IOException If the stream has never been marked, or if the mark has been invalidated synchronized (lock) { ensureOpen(); if (markedChar < 0) throw new IOException((markedChar == INVALIDATED) ? "Mark invalid" : "Stream not marked"); nextChar = markedChar; skipLF = markedSkipLF; }
public long	skip(long n) Skips characters. 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(); long r = n; while (r > 0) { if (nextChar >= nChars) fill(); if (nextChar >= nChars) /* EOF */ break; if (skipLF) { skipLF = false; if (cb[nextChar] == '\n") { nextChar++; } } long d = nChars - nextChar; if (r <= d) { nextChar += r; r = 0; break; } else { r -= d; nextChar = nChars; } } return n - r; }