java.lang.Object | |
↳ | java.io.InputStream |
Known Direct Subclasses |
A readable source of bytes.
Most clients will use input streams that read data from the file system
(FileInputStream
), the network (getInputStream()
/getInputStream()
), or from an in-memory byte
array (ByteArrayInputStream
).
Use InputStreamReader
to adapt a byte stream like this one into a
character stream.
Most clients should wrap their input stream with BufferedInputStream
. Callers that do only bulk reads may omit buffering.
Some implementations support marking a position in the input stream and
resetting back to this position later. Implementations that don't return
false from markSupported()
and throw an IOException
when
reset()
is called.
FilterInputStream
, which delegates all calls to the source input
stream.
All input stream subclasses should override both read()
and read(byte[],int,int)
. The
three argument overload is necessary for bulk access to the data. This is
much more efficient than byte-by-byte access.
Public Constructors | |||||||||||
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This constructor does nothing.
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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 this stream.
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Sets a mark position in this InputStream.
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Indicates whether this stream supports the
mark() and
reset() methods. | |||||||||||
Equivalent to
read(buffer, 0, buffer.length) . | |||||||||||
Reads a single byte from this stream and returns it as an integer in the
range from 0 to 255.
| |||||||||||
Reads up to
byteCount bytes from this stream and stores them in
the byte array buffer starting at byteOffset . | |||||||||||
Resets this stream to the last marked location.
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Skips at most
byteCount bytes in this stream. |
[Expand]
Inherited Methods | |||||||||||
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From class
java.lang.Object
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From interface
java.io.Closeable
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From interface
java.lang.AutoCloseable
|
This constructor does nothing. It is provided for signature compatibility.
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 | if this stream is closed or an error occurs |
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Closes this stream. Concrete implementations of this class should free any resources during close. This implementation does nothing.
IOException | if an error occurs while closing this stream. |
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Sets a mark position in this InputStream. The parameter readlimit
indicates how many bytes can be read before the mark is invalidated.
Sending reset()
will reposition the stream back to the marked
position provided readLimit
has not been surpassed.
This default implementation does nothing and concrete subclasses must provide their own implementation.
readlimit | the number of bytes that can be read from this stream before the mark is invalidated. |
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Equivalent to read(buffer, 0, buffer.length)
.
IOException |
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Reads a single byte from this stream and returns it as an integer in the range from 0 to 255. Returns -1 if the end of the stream has been reached. Blocks until one byte has been read, the end of the source stream is detected or an exception is thrown.
IOException | if the stream is closed or another IOException occurs. |
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Reads up to byteCount
bytes from this stream and stores them in
the byte array buffer
starting at byteOffset
.
Returns the number of bytes actually read or -1 if the end of the stream
has been reached.
IndexOutOfBoundsException | if byteOffset < 0 || byteCount < 0 || byteOffset + byteCount > buffer.length . |
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IOException | if the stream is closed or another IOException occurs. |
Resets this stream to the last marked location. Throws an
IOException
if the number of bytes read since the mark has been
set is greater than the limit provided to mark
, or if no mark
has been set.
This implementation always throws an IOException
and concrete
subclasses should provide the proper implementation.
IOException | if this stream is closed or another IOException occurs. |
---|
Skips at most byteCount
bytes in this stream. The number of actual
bytes skipped may be anywhere between 0 and byteCount
. If
byteCount
is negative, this method does nothing and returns 0, but
some subclasses may throw.
Note the "at most" in the description of this method: this method may choose to skip fewer bytes than requested. Callers should always check the return value.
This default implementation reads bytes into a temporary buffer. Concrete subclasses should provide their own implementation.
IOException | if this stream is closed or another IOException occurs. |
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