Chapter 11
The java.io Package

LineNumberInputStream

Name

Synopsis

Class Name:

java.io.LineNumberInputStream

Superclass:

java.io.FilterInputStream

Immediate Subclasses:

None

Interfaces Implemented:

None

Availability:

Deprecated as of JDK 1.1

The LineNumberInputStream class is an InputStream that keeps track of line numbers. The line number starts at 0 and is incremented each time an end-of-line character is encountered. LineNumberInputStream recognizes "\n", "\r", or "\r\n" as the end of a line. Regardless of the end-of-line character it reads, LineNumberInputStream returns only "\n". The current line number is returned by getLineNumber(). The mark() and reset() methods are supported, but only work if the underlying stream supports mark() and reset().

The LineNumberInputStream class is deprecated as of JDK 1.1 because it does not perform any byte to character conversions. Incoming bytes are directly compared to end-of-line characters. If you are developing new code, you should use LineNumberReader instead.

Class Summary

public class java.io.LineNumberInputStream 
             extends java.io.FilterInputStream {
  // Constructors
  public LineNumberInputStream(InputStream in);
  // Instance Methods
  public int available();
  public int getLineNumber();
  public void mark(int readlimit);
  public int read();
  public int read(byte[] b, int off, int len);
  public void reset();
  public void setLineNumber(int lineNumber);
  public long skip(long n);
}

Constructors

LineNumberInputStream

public LineNumberInputStream(InputStream in)

Parameters

in: The input stream to use.

Description

This constructor creates a LineNumberInputStream that gets its data from in.

Instance Methods

available

public int available() throws IOException

Returns

The number of bytes that can be read without blocking.

Throws

IOException: If any kind of I/O error occurs.

Overrides

FilterInputStream.available()

Description

This method returns the number of bytes of input that can be read without having to wait for more input to become available.

getLineNumber

public int getLineNumber()

Returns

The current line number.

Description

This method returns the current line number.

mark

public void mark(int readlimit)

Parameters

readlimit: The maximum number of bytes that can be read before the saved position becomes invalid.

Overrides

FilterInputStream.mark()

Description

This method tells the LineNumberInputStream to remember its current position. A subsequent call to reset() causes the object to return to that saved position and thus reread a portion of the input. The method calls the mark() method of the underlying stream, so it only works if the underlying stream supports mark() and reset().

read

public int read() throws IOException

Returns

The next byte of data or -1 if the end of the stream is encountered.

Throws

IOException: If any kind of I/O error occurs.

Overrides

FilterInputStream.read()

Description

This method reads a byte of input from the underlying stream. If "\n", "\r", or "\r\n" is read from the stream, "\n" is returned. Otherwise, the byte read from the underlying stream is returned verbatim. The method blocks until the byte is read, the end of stream is encountered, or an exception is thrown.

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

Parameters

b

An array of bytes to be filled from the stream.

off

An offset into the byte array.

len

The number of bytes to read.

Returns

The actual number of bytes read or -1 if the end of the stream is encountered immediately.

Throws

IOException: If any kind of I/O error occurs.

Overrides

FilterInputStream.read(byte[], int, int)

Description

This method reads up to len bytes of input into the given array starting at index off. If "\n", "\r", or "\r\n" is read from the stream, "\n" is returned. The method does this by repeatedly calling read(), which is not efficient, especially if the underlying stream is not buffered. The method blocks until some data is available.

reset

public void reset() throws IOException

Throws

IOException: If there was no previous call to this FilterInputStream's mark() method or the saved position has been invalidated.

Overrides

FilterInputStream.reset()

Description

This method calls the reset() method of the underlying stream. If the underlying stream supports mark() and reset(), this method sets the position of the stream to a position that was saved by a previous call to mark(). Subsequent bytes read from this stream will begin from the saved position and continue normally. The method also restores the line number to its correct value for the mark location. The method only works if the underlying stream supports mark() and reset().

setLineNumber

public void setLineNumber(int lineNumber)

Parameters

lineNumber: The new line number.

Description

This method sets the current line number of the LineNumberInputStream. The method does not change the position of the stream.

skip

public long skip(long n) throws IOException

Parameters

n: The number of bytes to skip.

Returns

The actual number of bytes skipped.

Throws

IOException: If any kind of I/O error occurs.

Overrides

FilterInputStream.skip()

Description

This method skips n bytes of input. Note that since LineNumberInputStream returns "\r\n" as a single character, "\n", this method may skip over more bytes than you expect.

Inherited Methods

Method	Inherited From	Method	Inherited From
`clone()`	`Object`	`close()`	`FilterInputStream`
`equals(Object)`	`Object`	`finalize()`	`Object`
`getClass()`	`Object`	`hashCode()`	`Object`
`markSupported()`	`FilterInputStream`	`notify()`	`Object`
`notifyAll()`	`Object`	`read(byte[])`	`FilterInputStream`
`toString()`	`Object`	`wait()`	`Object`
`wait(long)`	`Object`	`wait(long, int)`	`Object`