java.io

Class SequenceInputStream

java.lang.Object

java.io.InputStream

java.io.SequenceInputStream

All Implemented Interfaces:

Closeable

public class SequenceInputStream
extends InputStream

This class merges a sequence of multiple InputStream's in order to form a single logical stream that can be read by applications that expect only one stream.

The streams passed to the constructor method are read in order until they return -1 to indicate they are at end of stream. When a stream reports end of stream, it is closed, then the next stream is read. When the last stream is closed, the next attempt to read from this stream will return a -1 to indicate it is at end of stream.

If this stream is closed prior to all subordinate streams being read to completion, all subordinate streams are closed.

Author:

Aaron M. Renn (arenn@urbanophile.com), Warren Levy (warrenl@cygnus.com)

Constructor Summary

Constructors

Constructor and Description
SequenceInputStream(Enumeration<? extends InputStream> e) This method creates a new SequenceInputStream that obtains its list of subordinate InputStreams from the specified Enumeration
SequenceInputStream(InputStream s1, InputStream s2) This method creates a new SequenceInputStream that will read the two specified subordinate InputStreams in sequence.

Method Summary

Modifier and Type	Method and Description
int	available() This method returns the number of bytes than can be read from the currently being read subordinate stream before that stream could block.
void	close() Closes this stream.
int	read() This method reads an unsigned byte from the input stream and returns it as an int in the range of 0-255.
int	read(byte[] b, int off, int len) This method reads bytes from a stream and stores them into a caller supplied buffer.

Methods inherited from class java.io.InputStream

mark, markSupported, read, reset, skip

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SequenceInputStream

public SequenceInputStream(Enumeration<? extends InputStream> e)

This method creates a new SequenceInputStream that obtains its list of subordinate InputStreams from the specified Enumeration

Parameters:

e - An Enumeration that will return a list of InputStreams to read in sequence

SequenceInputStream

public SequenceInputStream(InputStream s1,
                           InputStream s2)

This method creates a new SequenceInputStream that will read the two specified subordinate InputStreams in sequence.

Parameters:

s1 - The first InputStream to read

s2 - The second InputStream to read

Method Detail

available

public int available()
              throws IOException

This method returns the number of bytes than can be read from the currently being read subordinate stream before that stream could block. Note that it is possible more bytes than this can actually be read without the stream blocking. If a 0 is returned, then the stream could block on the very next read.

Overrides:

available in class InputStream

Returns:

The number of bytes that can be read before blocking could occur

Throws:

IOException - If an error occurs

close

public void close()
           throws IOException

Closes this stream. This will cause any remaining unclosed subordinate InputStream's to be closed as well. Subsequent attempts to read from this stream may cause an exception.

Specified by:

close in interface Closeable

Overrides:

close in class InputStream

Throws:

IOException - If an error occurs

read

public int read()
         throws IOException

This method reads an unsigned byte from the input stream and returns it as an int in the range of 0-255. This method also will return -1 if the end of the stream has been reached. This will only happen when all of the subordinate streams have been read.

This method will block until the byte can be read.

Specified by:

read in class InputStream

Returns:

The byte read, or -1 if end of stream

Throws:

IOException - If an error occurs

read

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

This method reads bytes from a stream and stores them into a caller supplied buffer. It starts storing the data at index offset into the buffer and attempts to read len bytes. This method can return before reading the number of bytes requested. The actual number of bytes read is returned as an int. A -1 is returend to indicate the end of the stream. This will only happen when all of the subordinate streams have been read.

This method will block until at least one byte can be read.

Overrides:

read in class InputStream

Parameters:

b - The array into which bytes read should be stored

off - The offset into the array to start storing bytes

len - The requested number of bytes to read

Returns:

The actual number of bytes read, or -1 if end of stream

Throws:

IOException - If an error occurs