Package java.io

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Class LineNumberInputStream

public  class  java.io.LineNumberInputStream
    extends  java.io.FilterInputStream  
{
        // Constructors
    public LineNumberInputStream(InputStream  in);	

        // 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);	
}

This class is an input stream filter that provides the added functionality of keeping track of the current line number.

A line is a sequence of bytes ending with either a carriage return character ('\r'), a newline character ('\n'), or a carriage return character followed immediately by a line feed character. In all three cases the line terminating character(s) are returned as a single newline character.

The line number begins at zero, and is incremented by 1 when a read returns a newline character.

Constructors

LineNumberInputStream

public LineNumberInputStream(InputStream  in) 

Constructs a new line number input stream that reads its input from the specified input stream.

Parameter	Description
in	the underlying input stream

Methods

available

public int available() 

throws IOException 

Determines the number of bytes that can be read from this input stream without blocking.

Note that if the underlying input stream is able to supply k input characters without blocking, the LineNumberInputStream can guarantee only to provide k/2 characters without blocking, because the k characters from the underlyhing input stream might consist of k/2 pairs of '\r' and '\n', which are converted to just k/2 '\n' characters.

Return Value:

Returns the number of bytes that can be read from this input stream without blocking.

Throw:

IOException

If an I/O error occurs.

Overrides:

available in class FilterInputStream .

getLineNumber

public int getLineNumber() 

Return Value:

Returns the current line number.

mark

public void mark(int  readlimit) 

Marks the current position in this input stream. A subsequent call to the reset method repositions this stream at the last marked position so that subsequent reads re-read the same bytes.

The mark method of LineNumberInputStream remembers the current line number in a private variable, and then calls the mark method of the underlying input stream .

Parameter	Description
readlimit	the maximum limit of bytes that can be read before the mark position becomes invalid.

Overrides:

mark in class FilterInputStream .

read

public int read() 

throws IOException 

Reads the next byte of data from this input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until either input data is available, the end of the stream is detected, or an exception is thrown.

The read method of LineNumberInputStream calls the read method of the underlying input stream . It checks for carriage returns and newline characters in the input, and modifies the current line number as appropriate. A carriage return character or a carriage return followed by a newline character are both converted into a single newline character.

Return Value:

Returns the next byte of data, or -1 if the end of this stream is reached

Throw:

IOException

If an I/O error occurs.

Overrides:

read in class FilterInputStream .

read

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

throws IOException 

Reads up to len bytes of data from this input stream into an array of bytes. This method blocks until some input is available.

The read method of LineNumberInputStream repeatedly calls the read method of zero arguments to fill in the byte array.

Return Value:

Returns the total number of bytes read into the buffer, or -1 is there is no more data because the end of this stream has been reached.

Parameter	Description
b	the buffer into which the data is read
off	the start offset of the data
len	the maximum number of bytes read

Throw:

IOException

If an I/O error occurs.

Overrides:

read in class FilterInputStream .

reset

public void reset() 

throws IOException 

Repositions this stream to the position at the time the mark method was last called on this input stream.

The reset method of LineNumberInputStream resets the line number to be the line number at the time the mark method was called, and then calls the mark method of the underlying input stream .

Throw:

IOException

If an I/O error occurs.

Overrides:

reset in class FilterInputStream .

setLineNumber

public void setLineNumber(int  lineNumber) 

Sets the line number to the specified argument.

Parameter	Description
lineNumber	the new line number

skip

public long skip(long  n) 

throws IOException 

Skips over and discards n bytes of data from the input stream. The skip method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly zero. The actual number of bytes skipped is returned.

The skip method of LineNumberInputStream creates a byte array of length n and then reads into it until n bytes have been read or the end of the stream has been reached.

Return Value:

Returns the actual number of bytes skipped.

Parameter	Description
n	the number of bytes to be skipped

Throw:

IOException

If an I/O error occurs.

Overrides:

skip in class FilterInputStream .