java.lang.Object | ||
↳ | java.io.InputStream | |
↳ | java.io.SequenceInputStream |
Concatenates two or more existing InputStream
s. Reads are taken from
the first stream until it ends, then the next stream is used, until the last
stream returns end of file.
Public Constructors | |||||||||||
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Constructs a new
SequenceInputStream using the two streams
s1 and s2 as the sequence of streams to read from. | |||||||||||
Constructs a new SequenceInputStream using the elements returned from
Enumeration
e as the stream sequence. |
Public Methods | |||||||||||
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Returns an estimated number of bytes that can be read or skipped without blocking for more
input.
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Closes all streams in this sequence of input stream.
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Reads at most
count bytes from this sequence of input streams and
stores them in the byte array buffer starting at offset . | |||||||||||
Reads a single byte from this sequence of input streams and returns it as
an integer in the range from 0 to 255.
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Inherited Methods | |||||||||||
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From class java.io.InputStream
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From class java.lang.Object
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From interface java.io.Closeable
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Constructs a new SequenceInputStream
using the two streams
s1
and s2
as the sequence of streams to read from.
s1 | the first stream to get bytes from. |
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s2 | the second stream to get bytes from. |
NullPointerException | if s1 is null .
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Constructs a new SequenceInputStream using the elements returned from
Enumeration e
as the stream sequence. The instances returned by
e.nextElement()
must be of type InputStream
.
e | the enumeration of InputStreams to get bytes from. |
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NullPointerException | if any of the elements in e is null .
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Returns an estimated number of bytes that can be read or skipped without blocking for more input.
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, 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
racy).
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
available.
IOException |
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Closes all streams in this sequence of input stream.
IOException | if an error occurs while closing any of the input streams. |
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Reads at most count
bytes from this sequence of input streams and
stores them in the byte array buffer
starting at 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
requested by 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. |
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offset | the initial position in buffer to store the bytes read
from this stream. |
count | the maximum number of bytes to store in buffer . |
IndexOutOfBoundsException | if offset < 0 or count < 0 , or if offset + count is greater than the size of buffer . |
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IOException | if an I/O error occurs. |
NullPointerException | if buffer is null .
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Reads a single byte from this sequence of input streams and returns it as an integer in the range from 0 to 255. It tries to read from the current stream first; if the end of this stream has been reached, it reads from the next one. Blocks until one byte has been read, the end of the last input stream in the sequence has been reached, or an exception is thrown.
IOException | if an error occurs while reading the current source input stream. |
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