By default, line numbering begins at 0. This number increments at every * line terminator as the data is read, and at the end of the * stream if the last character in the stream is not a line terminator. This * number can be changed with a call to {@code setLineNumber(int)}. Note * however, that {@code setLineNumber(int)} does not actually change the current * position in the stream; it only changes the value that will be returned by * {@code getLineNumber()}. * *
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. * * @author Mark Reinhold * @since 1.1 */ public class LineNumberReader extends BufferedReader { /** Previous character types */ private static final int NONE = 0; // no previous character private static final int CHAR = 1; // non-line terminator private static final int EOL = 2; // line terminator private static final int EOF = 3; // end-of-file /** The previous character type */ private int prevChar = NONE; /** The current line number */ private int lineNumber = 0; /** The line number of the mark, if any */ private int markedLineNumber; // Defaults to 0 /** If the next character is a line feed, skip it */ private boolean skipLF; /** The skipLF flag when the mark was set */ private boolean markedSkipLF; /** * Create a new line-numbering reader, using the default input-buffer * size. * * @param in * A Reader object to provide the underlying stream */ public LineNumberReader(Reader in) { super(in); } /** * Create a new line-numbering reader, reading characters into a buffer of * the given size. * * @param in * A Reader object to provide the underlying stream * * @param sz * An int specifying the size of the buffer */ public LineNumberReader(Reader in, int sz) { super(in, sz); } /** * Set the current line number. * * @param lineNumber * An int specifying the line number * * @see #getLineNumber */ public void setLineNumber(int lineNumber) { this.lineNumber = lineNumber; } /** * Get the current line number. * * @return The current line number * * @see #setLineNumber */ public int getLineNumber() { return lineNumber; } /** * Read a single character. Line terminators are * compressed into single newline ('\n') characters. The current line * number is incremented whenever a line terminator is read, or when the * end of the stream is reached and the last character in the stream is * not a line terminator. * * @return The character read, or -1 if the end of the stream has been * reached * * @throws IOException * If an I/O error occurs */ @SuppressWarnings("fallthrough") public int read() throws IOException { synchronized (lock) { int c = super.read(); if (skipLF) { if (c == '\n') c = super.read(); skipLF = false; } switch (c) { case '\r': skipLF = true; case '\n': /* Fall through */ lineNumber++; prevChar = EOL; return '\n'; case -1: if (prevChar == CHAR) lineNumber++; prevChar = EOF; break; default: prevChar = CHAR; break; } return c; } } /** * Read characters into a portion of an array. The current line * number is incremented whenever a line terminator is read, or when the * end of the stream is reached and the last character in the stream is * not a line terminator. * * @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 bytes read, or -1 if the end of the stream has * already been reached * * @throws IOException * If an I/O error occurs * * @throws IndexOutOfBoundsException {@inheritDoc} */ @SuppressWarnings("fallthrough") public int read(char cbuf[], int off, int len) throws IOException { synchronized (lock) { int n = super.read(cbuf, off, len); if (n == -1) { if (prevChar == CHAR) lineNumber++; prevChar = EOF; return -1; } for (int i = off; i < off + n; i++) { int c = cbuf[i]; if (skipLF) { skipLF = false; if (c == '\n') continue; } switch (c) { case '\r': skipLF = true; case '\n': /* Fall through */ lineNumber++; break; } } if (n > 0) { switch ((int)cbuf[off + n - 1]) { case '\r': case '\n': /* Fall through */ prevChar = EOL; break; default: prevChar = CHAR; break; } } return n; } } /** * Read a line of text. The current line number is incremented whenever * a line terminator is read, or when the end of the stream is reached and * the last character in the stream is not a line terminator. * * @return A String containing the contents of the line, not including * any line termination characters, or * {@code null} if the end of the stream has been reached * * @throws IOException * If an I/O error occurs */ public String readLine() throws IOException { synchronized (lock) { boolean[] term = new boolean[1]; String l = super.readLine(skipLF, term); skipLF = false; if (l != null) { lineNumber++; prevChar = term[0] ? EOL : EOF; } else { // l == null if (prevChar == CHAR) lineNumber++; prevChar = EOF; } return l; } } /** Maximum skip-buffer size */ private static final int maxSkipBufferSize = 8192; /** Skip buffer, null until allocated */ private char skipBuffer[] = null; /** * Skip characters. * * @param n * The number of characters to skip * * @return The number of characters actually skipped * * @throws IOException * If an I/O error occurs * * @throws IllegalArgumentException * If {@code n} is negative */ public long skip(long n) throws IOException { if (n < 0) 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; } if (n - r > 0) { prevChar = NONE; } return n - r; } } /** * Mark the present position in the stream. Subsequent calls to reset() * will attempt to reposition the stream to this point, and will also reset * the line number appropriately. * * @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. * * @throws IOException * If an I/O error occurs */ public void mark(int readAheadLimit) throws IOException { synchronized (lock) { // If the most recently read character is '\r', then increment the // read ahead limit as in this case if the next character is '\n', // two characters would actually be read by the next read(). if (skipLF) readAheadLimit++; super.mark(readAheadLimit); markedLineNumber = lineNumber; markedSkipLF = skipLF; } } /** * Reset the stream to the most recent mark. * * @throws IOException * If the stream has not been marked, or if the mark has been * invalidated */ public void reset() throws IOException { synchronized (lock) { super.reset(); lineNumber = markedLineNumber; skipLF = markedSkipLF; } } }