22.12 The Class java.io.LineNumberInputStream

A LineNumberInputStream adds functionality to another input stream, namely the ability to count lines. When the LineNumberInputStream is created, the line number counter is set to zero. As bytes from the stream are read or skipped, the counter is incremented whenever a line terminator (\n, \r, or \r\n) is encountered. Such line terminators are also converted to a single '\n' character. The method getLineNumber returns the current value of the counter, and the method setLineNumber sets the counter to a given integer value. If the contained input stream supports the mark operation, then so does the LineNumberInputStream; the mark operation remembers the line number counter and the reset operation sets the counter to the value remembered by the mark operation.

public class LineNumberInputStream extends FilterInputStream {
	public LineNumberInputStream(InputStream in);
	public int read() throws IOException;
	public int read(byte[] b)
		throws IOException, NullPointerException;
	public int read(byte[] b, int off, int len)

		throws IOException, NullPointerException,
			IndexOutOfBoundsException;
	public long skip(long n) throws IOException;
	public int available() throws IOException;
	public void mark(int readlimit);
	public void reset() throws IOException;
	public int getLineNumber();
	public void setLineNumber(int lineNumber);
}

22.12.1 public LineNumberInputStream(InputStream in)

This constructor initializes a newly created LineNumberInputStream by saving its argument, the input stream in, for later use.

22.12.2 public int read() throws IOException

See the general contract of the read method of InputStream (§22.3.1).

As bytes are read from the contained input stream, line terminators are recognized and counted. For each line terminator recognized in the contained input stream, a single character '\n' is returned.

Overrides the read method of FilterInputStream (§22.9.3).

22.12.3 public int read(byte[] b)
throws IOException, NullPointerException

See the general contract of the read method of InputStream (§22.3.2).

As bytes are read from the contained input stream, line terminators are recognized and counted. For each line terminator recognized in the contained input stream, a single character '\n' is returned.

Overrides the read method of FilterInputStream (§22.9.4).

22.12.4 public int read(byte[] b, int off, int len)
throws IOException, NullPointerException, IndexOutOfBoundsException

See the general contract of the read method of InputStream (§22.3.3).

As bytes are read from the contained input stream, line terminators are recognized and counted. For each line terminator recognized in the contained input stream, a single character '\n' is returned.

Overrides the read method of FilterInputStream (§22.9.5).

22.12.5 public long skip(long n) throws IOException

See the general contract of the skip method of InputStream (§22.3.4).

As bytes are read from the contained input stream, line terminators are recognized and counted. Each line terminator recognized in the contained input stream is considered to be a single byte skipped, even if it is the sequence \r\n.

Overrides the skip method of FilterInputStream (§22.9.6).

22.12.6 public int available() throws IOException

See the general contract of the available method of InputStream (§22.3.5).

Note that if the contained input stream is able to supply k input characters without blocking, the LineNumberInputStream can guarantee only to provide characters without blocking, because the k characters from the contained input stream might consist of \r\n pairs, which will be converted to just '\n' characters.

Overrides the available method of FilterInputStream (§22.9.7).

22.12.7 public void mark(int readlimit)

See the general contract of the mark method of InputStream (§22.3.7).

Marking a point in the input stream remembers the current line number as it would be returned by getLineNumber (§22.12.9).

Overrides the mark method of FilterInputStream (§22.9.9).

22.12.8 public void reset() throws IOException

See the general contract of the reset method of InputStream (§22.3.8).

Resetting the input stream to a previous point also resets the line number to the value it had at the marked point.

Overrides the reset method of FilterInputStream (§22.9.10).

22.12.9 public int getLineNumber()

The current line number is returned. This quantity depends on k, the number of line terminators encountered since the most recent occurrence of one of the following three kinds of events:

• If a call to the setLineNumber method was most recent, let n be the argument that was given to setLineNumber; then the current line number is .
• If a call to the reset method was most recent, let m be the line number that had been remembered by mark; then the current line number is .
• If creation of the LineNumberInputStream was most recent (that is, neither of the other kinds of event have occurred), then the current line number is k.

These rules imply that the current line number is 0 as the characters of the first line are read, and becomes 1 after the line terminator for the first line has been read.

22.12.10 public void setLineNumber(int lineNumber)

The current line number is set equal to the argument.