Closeable
, AutoCloseable
AudioInputStream
, ByteArrayInputStream
, FileInputStream
, FilterInputStream
, ObjectInputStream
, PipedInputStream
, SequenceInputStream
, StringBufferInputStream
public abstract class InputStream extends Object implements Closeable
Applications that need to define a subclass of InputStream
must always provide a method that returns the next byte of input.
Constructor | Description |
---|---|
InputStream() |
Constructor for subclasses to call. |
Modifier and Type | Method | Description |
---|---|---|
int |
available() |
Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking, which may be 0, or 0 when end of stream is detected. |
void |
close() |
Closes this input stream and releases any system resources associated with the stream. |
void |
mark |
Marks the current position in this input stream. |
boolean |
markSupported() |
Tests if this input stream supports the mark and reset methods. |
static InputStream |
nullInputStream() |
Returns a new InputStream that reads no bytes. |
abstract int |
read() |
Reads the next byte of data from the input stream. |
int |
read |
Reads some number of bytes from the input stream and stores them into the buffer array b . |
int |
read |
Reads up to len bytes of data from the input stream into an array of bytes. |
byte[] |
readAllBytes() |
Reads all remaining bytes from the input stream. |
int |
readNBytes |
Reads the requested number of bytes from the input stream into the given byte array. |
byte[] |
readNBytes |
Reads up to a specified number of bytes from the input stream. |
void |
reset() |
Repositions this stream to the position at the time the mark method was last called on this input stream. |
long |
skip |
Skips over and discards n bytes of data from this input stream. |
void |
skipNBytes |
Skips over and discards exactly n bytes of data from this input stream. |
long |
transferTo |
Reads all bytes from this input stream and writes the bytes to the given output stream in the order that they are read. |
public InputStream()
public static InputStream nullInputStream()
InputStream
that reads no bytes. The returned stream is initially open. The stream is closed by calling the close()
method. Subsequent calls to close()
have no effect. While the stream is open, the available()
, read()
, read(byte[])
, read(byte[], int, int)
, readAllBytes()
, readNBytes(byte[], int, int)
, readNBytes(int)
, skip(long)
, skipNBytes(long)
, and transferTo()
methods all behave as if end of stream has been reached. After the stream has been closed, these methods all throw IOException
.
The markSupported()
method returns false
. The mark()
method does nothing, and the reset()
method throws IOException
.
InputStream
which contains no bytespublic abstract int read() throws IOException
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 input data is available, the end of the stream is detected, or an exception is thrown.-1
if the end of the stream is reached.IOException
- if an I/O error occurs.public int read(byte[] b) throws IOException
b
. The number of bytes actually read is returned as an integer. This method blocks until input data is available, end of file is detected, or an exception is thrown. If the length of b
is zero, then no bytes are read and 0
is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at the end of the file, the value -1
is returned; otherwise, at least one byte is read and stored into b
.
The first byte read is stored into element b[0]
, the next one into b[1]
, and so on. The number of bytes read is, at most, equal to the length of b
. Let k be the number of bytes actually read; these bytes will be stored in elements b[0]
through b[
k-1]
, leaving elements b[
k]
through b[b.length-1]
unaffected.
read(b)
method for class InputStream
has the same effect as: read(b, 0, b.length)
b
- the buffer into which the data is read.-1
if there is no more data because the end of the stream has been reached.IOException
- If the first byte cannot be read for any reason other than the end of the file, if the input stream has been closed, or if some other I/O error occurs.NullPointerException
- if b
is null
.public int read(byte[] b, int off, int len) throws IOException
len
bytes of data from the input stream into an array of bytes. An attempt is made to read as many as len
bytes, but a smaller number may be read. The number of bytes actually read is returned as an integer. This method blocks until input data is available, end of file is detected, or an exception is thrown.
If len
is zero, then no bytes are read and 0
is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1
is returned; otherwise, at least one byte is read and stored into b
.
The first byte read is stored into element b[off]
, the next one into b[off+1]
, and so on. The number of bytes read is, at most, equal to len
. Let k be the number of bytes actually read; these bytes will be stored in elements b[off]
through b[off+
k-1]
, leaving elements b[off+
k]
through b[off+len-1]
unaffected.
In every case, elements b[0]
through b[off-1]
and elements b[off+len]
through b[b.length-1]
are unaffected.
read(b, off, len)
method for class InputStream
simply calls the method read()
repeatedly. If the first such call results in an IOException
, that exception is returned from the call to the read(b,
off,
len)
method. If any subsequent call to read()
results in a IOException
, the exception is caught and treated as if it were end of file; the bytes read up to that point are stored into b
and the number of bytes read before the exception occurred is returned. The default implementation of this method blocks until the requested amount of input data len
has been read, end of file is detected, or an exception is thrown. Subclasses are encouraged to provide a more efficient implementation of this method.b
- the buffer into which the data is read.off
- the start offset in array b
at which the data is written.len
- the maximum number of bytes to read.-1
if there is no more data because the end of the stream has been reached.IOException
- If the first byte cannot be read for any reason other than end of file, or if the input stream has been closed, or if some other I/O error occurs.NullPointerException
- If b
is null
.IndexOutOfBoundsException
- If off
is negative, len
is negative, or len
is greater than b.length - off
public byte[] readAllBytes() throws IOException
When this stream reaches end of stream, further invocations of this method will return an empty byte array.
Note that this method is intended for simple cases where it is convenient to read all bytes into a byte array. It is not intended for reading input streams with large amounts of data.
The behavior for the case where the input stream is asynchronously closed, or the thread interrupted during the read, is highly input stream specific, and therefore not specified.
If an I/O error occurs reading from the input stream, then it may do so after some, but not all, bytes have been read. Consequently the input stream may not be at end of stream and may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.
readNBytes(int)
with a length of Integer.MAX_VALUE
.IOException
- if an I/O error occursOutOfMemoryError
- if an array of the required size cannot be allocated.public byte[] readNBytes(int len) throws IOException
The length of the returned array equals the number of bytes read from the stream. If len
is zero, then no bytes are read and an empty byte array is returned. Otherwise, up to len
bytes are read from the stream. Fewer than len
bytes may be read if end of stream is encountered.
When this stream reaches end of stream, further invocations of this method will return an empty byte array.
Note that this method is intended for simple cases where it is convenient to read the specified number of bytes into a byte array. The total amount of memory allocated by this method is proportional to the number of bytes read from the stream which is bounded by len
. Therefore, the method may be safely called with very large values of len
provided sufficient memory is available.
The behavior for the case where the input stream is asynchronously closed, or the thread interrupted during the read, is highly input stream specific, and therefore not specified.
If an I/O error occurs reading from the input stream, then it may do so after some, but not all, bytes have been read. Consequently the input stream may not be at end of stream and may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.
2*(long)len
, inclusive.len
- the maximum number of bytes to readIllegalArgumentException
- if length
is negativeIOException
- if an I/O error occursOutOfMemoryError
- if an array of the required size cannot be allocated.public int readNBytes(byte[] b, int off, int len) throws IOException
len
bytes of input data have been read, end of stream is detected, or an exception is thrown. The number of bytes actually read, possibly zero, is returned. This method does not close the input stream. In the case where end of stream is reached before len
bytes have been read, then the actual number of bytes read will be returned. When this stream reaches end of stream, further invocations of this method will return zero.
If len
is zero, then no bytes are read and 0
is returned; otherwise, there is an attempt to read up to len
bytes.
The first byte read is stored into element b[off]
, the next one in to b[off+1]
, and so on. The number of bytes read is, at most, equal to len
. Let k be the number of bytes actually read; these bytes will be stored in elements b[off]
through b[off+
k-1]
, leaving elements b[off+
k ]
through b[off+len-1]
unaffected.
The behavior for the case where the input stream is asynchronously closed, or the thread interrupted during the read, is highly input stream specific, and therefore not specified.
If an I/O error occurs reading from the input stream, then it may do so after some, but not all, bytes of b
have been updated with data from the input stream. Consequently the input stream and b
may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.
b
- the byte array into which the data is readoff
- the start offset in b
at which the data is writtenlen
- the maximum number of bytes to readIOException
- if an I/O error occursNullPointerException
- if b
is null
IndexOutOfBoundsException
- If off
is negative, len
is negative, or len
is greater than b.length - off
public long skip(long n) throws IOException
n
bytes of data from this input stream. The skip
method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly 0
. This may result from any of a number of conditions; reaching end of file before n
bytes have been skipped is only one possibility. The actual number of bytes skipped is returned. If n
is negative, the skip
method for class InputStream
always returns 0, and no bytes are skipped. Subclasses may handle the negative value differently.skip
method implementation of this class creates a byte array and then repeatedly reads into it until n
bytes have been read or the end of the stream has been reached. Subclasses are encouraged to provide a more efficient implementation of this method. For instance, the implementation may depend on the ability to seek.n
- the number of bytes to be skipped.IOException
- if an I/O error occurs.public void skipNBytes(long n) throws IOException
n
bytes of data from this input stream. If n
is zero, then no bytes are skipped. If n
is negative, then no bytes are skipped. Subclasses may handle the negative value differently. This method blocks until the requested number of bytes has been skipped, end of file is reached, or an exception is thrown.
If end of stream is reached before the stream is at the desired position, then an EOFException
is thrown.
If an I/O error occurs, then the input stream may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.
n
is zero or negative, then no bytes are skipped. If n
is positive, the default implementation of this method invokes skip()
repeatedly with its parameter equal to the remaining number of bytes to skip until the requested number of bytes has been skipped or an error condition occurs. If at any point the return value of skip()
is negative or greater than the remaining number of bytes to be skipped, then an IOException
is thrown. If skip()
ever returns zero, then read()
is invoked to read a single byte, and if it returns -1
, then an EOFException
is thrown. Any exception thrown by skip()
or read()
will be propagated.n
- the number of bytes to be skipped.EOFException
- if end of stream is encountered before the stream can be positioned n
bytes beyond its position when this method was invoked.IOException
- if the stream cannot be positioned properly or if an I/O error occurs.public int available() throws IOException
Note that while some implementations of InputStream
will return the total number of bytes in the stream, many will not. It is never correct to use the return value of this method to allocate a buffer intended to hold all data in this stream.
A subclass's implementation of this method may choose to throw an IOException
if this input stream has been closed by invoking the close()
method.
available
method of InputStream
always returns 0
.0
when it reaches the end of the input stream.IOException
- if an I/O error occurs.public void close() throws IOException
close
in interface AutoCloseable
close
in interface Closeable
close
method of InputStream
does nothing.IOException
- if an I/O error occurs.public void mark(int readlimit)
reset
method repositions this stream at the last marked position so that subsequent reads re-read the same bytes. The readlimit
arguments tells this input stream to allow that many bytes to be read before the mark position gets invalidated.
The general contract of mark
is that, if the method markSupported
returns true
, the stream somehow remembers all the bytes read after the call to mark
and stands ready to supply those same bytes again if and whenever the method reset
is called. However, the stream is not required to remember any data at all if more than readlimit
bytes are read from the stream before reset
is called.
Marking a closed stream should not have any effect on the stream.
mark
method of InputStream
does nothing.readlimit
- the maximum limit of bytes that can be read before the mark position becomes invalid.public void reset() throws IOException
mark
method was last called on this input stream. The general contract of reset
is:
markSupported
returns true
, then: mark
has not been called since the stream was created, or the number of bytes read from the stream since mark
was last called is larger than the argument to mark
at that last call, then an IOException
might be thrown. IOException
is not thrown, then the stream is reset to a state such that all the bytes read since the most recent call to mark
(or since the start of the file, if mark
has not been called) will be resupplied to subsequent callers of the read
method, followed by any bytes that otherwise would have been the next input data as of the time of the call to reset
. markSupported
returns false
, then: reset
may throw an IOException
. IOException
is not thrown, then the stream is reset to a fixed state that depends on the particular type of the input stream and how it was created. The bytes that will be supplied to subsequent callers of the read
method depend on the particular type of the input stream. reset
for class InputStream
does nothing except throw an IOException
.IOException
- if this stream has not been marked or if the mark has been invalidated.public boolean markSupported()
mark
and reset
methods. Whether or not mark
and reset
are supported is an invariant property of a particular input stream instance.markSupported
method of InputStream
returns false
.true
if this stream instance supports the mark and reset methods; false
otherwise.public long transferTo(OutputStream out) throws IOException
This method may block indefinitely reading from the input stream, or writing to the output stream. The behavior for the case where the input and/or output stream is asynchronously closed, or the thread interrupted during the transfer, is highly input and output stream specific, and therefore not specified.
If the total number of bytes transferred is greater than Long.MAX_VALUE, then Long.MAX_VALUE
will be returned.
If an I/O error occurs reading from the input stream or writing to the output stream, then it may do so after some bytes have been read or written. Consequently the input stream may not be at end of stream and one, or both, streams may be in an inconsistent state. It is strongly recommended that both streams be promptly closed if an I/O error occurs.
out
- the output stream, non-nullIOException
- if an I/O error occurs when reading or writingNullPointerException
- if out
is null
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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/io/InputStream.html