|Constructor and Description|
Constructs a new SequenceInputStream using the elements returned from Enumeration
Constructs a new
|Modifier and Type||Method and Description|
Returns an estimated number of bytes that can be read or skipped without blocking for more input.
Closes all streams in this sequence of input stream.
Reads a single byte from this sequence of input streams and returns it as an integer in the range from 0 to 255.
Reads at most
public SequenceInputStream(InputStream s1, InputStream s2)
SequenceInputStreamusing the two streams
s2as the sequence of streams to read from.
s1- the first stream to get bytes from.
s2- the second stream to get bytes from.
public SequenceInputStream(Enumeration<? extends InputStream> e)
eas the stream sequence. The instances returned by
e.nextElement()must be of type
e- the enumeration of
InputStreamsto get bytes from.
NullPointerException- if any of the elements in
public int available() throws IOException
Note that this method provides such a weak guarantee that it is not very useful in practice.
Firstly, the guarantee is "without blocking for more input" rather than "without blocking": a read may still block waiting for I/O to complete — the guarantee is merely that it won't have to wait indefinitely for data to be written. The result of this method should not be used as a license to do I/O on a thread that shouldn't be blocked.
Secondly, the result is a conservative estimate and may be significantly smaller than the actual number of bytes available. In particular, an implementation that always returns 0 would be correct. In general, callers should only use this method if they'd be satisfied with treating the result as a boolean yes or no answer to the question "is there definitely data ready?".
Thirdly, the fact that a given number of bytes is "available" does not guarantee that a read or skip will actually read or skip that many bytes: they may read or skip fewer.
It is particularly important to realize that you must not use this method to
size a container and assume that you can read the entirety of the stream without needing
to resize the container. Such callers should probably write everything they read to a
ByteArrayOutputStream and convert that to a byte array. Alternatively, if you're
reading from a file,
File.length() returns the current length of the file (though
assuming the file's length can't change may be incorrect, reading a file is inherently
The default implementation of this method in
InputStream always returns 0.
Subclasses should override this method if they are able to indicate the number of bytes
public void close() throws IOException
public int read() throws IOException
public int read(byte buffer, int offset, int count) throws IOException
countbytes from this sequence of input streams and stores them in the byte array
offset. Blocks only until at least 1 byte has been read, the end of the stream has been reached, or an exception is thrown.
This SequenceInputStream shows the same behavior as other InputStreams.
To do this it will read only as many bytes as a call to read on the
current substream returns. If that call does not return as many bytes as
count, it will not retry to read more on its own
because subsequent reads might block. This would violate the rule that
it will only block until at least one byte has been read.
If a substream has already reached the end when this call is made, it will close that substream and start with the next one. If there are no more substreams it will return -1.
buffer- the array in which to store the bytes read.
offset- the initial position in
bufferto store the bytes read from this stream.
count- the maximum number of bytes to store in
offset < 0or
count < 0, or if
offset + countis greater than the size of
IOException- if an I/O error occurs.