OpenJDK 27 · java.io.PushbackInputStream · APIdia, the JavaDoc alternative

Modifier and Type	Field and Description
protected byte[]	buf The pushback buffer.
protected int	pos The position within the pushback buffer from which the next byte will be read.

Access	Constructor and Description
public	PushbackInputStream(InputStream the input stream from which bytes will be read. in, int the size of the pushback buffer. size) Creates a `PushbackInputStream` with a pushback buffer of the specified `size`, and saves its argument, the input stream `in`, for later use.
public	PushbackInputStream(InputStream the input stream from which bytes will be read. in) Creates a `PushbackInputStream` with a 1-byte pushback buffer, and saves its argument, the input stream `in`, for later use.

Method Summary

Modifier and Type	Method and Description
public int	Returns: the number of bytes that can be read (or skipped over) from the input stream without blocking. available() Overrides java.io.FilterInputStream.available. Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream.
public synchronized void	close() Overrides java.io.FilterInputStream.close. Implements java.io.Closeable.close. Closes this input stream and releases any system resources associated with the stream.
private void	ensureOpen() Check to make sure that this stream has not been closed
public void	mark(int the maximum limit of bytes that can be read before the mark position becomes invalid. readlimit) Overrides java.io.FilterInputStream.mark. Marks the current position in this input stream.
public boolean	Returns: `false`, since this class does not support the `mark` and `reset` methods. markSupported() Overrides java.io.FilterInputStream.markSupported. Tests if this input stream supports the `mark` and `reset` methods, which it does not.
public int	Returns: the next byte of data, or `-1` if the end of the stream has been reached. read() Overrides java.io.FilterInputStream.read. Reads the next byte of data from this input stream.
public int	Returns: the total number of bytes read into the buffer, or `-1` if there is no more data because the end of the stream has been reached. read(byte[] the buffer into which the data is read. b, int the start offset in the destination array `b` off, int the maximum number of bytes read. len) Overrides java.io.FilterInputStream.read. Reads up to `len` bytes of data from this input stream into an array of bytes.
public void	reset() Overrides java.io.FilterInputStream.reset. Repositions this stream to the position at the time the `mark` method was last called on this input stream.
public long	skip(long n) Overrides java.io.FilterInputStream.skip. Skips over and discards `n` bytes of data from this input stream.
public long	transferTo(OutputStream out) Overrides java.io.InputStream.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 void	unread(int the `int` value whose low-order byte is to be pushed back. b) Pushes back a byte by copying it to the front of the pushback buffer.
public void	unread(byte[] the byte array to push back. b, int the start offset of the data. off, int the number of bytes to push back. len) Pushes back a portion of an array of bytes by copying it to the front of the pushback buffer.
public void	unread(byte[] the byte array to push back b) Pushes back an array of bytes by copying it to the front of the pushback buffer.

Inherited from java.io.FilterInputStream:: read

buf	back to summary
protected byte[] buf The pushback buffer. Since 1.1

pos	back to summary
protected int pos The position within the pushback buffer from which the next byte will be read. When the buffer is empty, `pos` is equal to `buf.length`; when the buffer is full, `pos` is equal to zero. Since 1.1

PushbackInputStream	back to summary
public PushbackInputStream(InputStream in, int size) Creates a `PushbackInputStream` with a pushback buffer of the specified `size`, and saves its argument, the input stream `in`, for later use. Initially, the pushback buffer is empty. Parameters in:InputStream the input stream from which bytes will be read. size:int the size of the pushback buffer. Exceptions IllegalArgumentException: if `size <= 0` Since 1.1

PushbackInputStream	back to summary
public PushbackInputStream(InputStream in) Creates a `PushbackInputStream` with a 1-byte pushback buffer, and saves its argument, the input stream `in`, for later use. Initially, the pushback buffer is empty. Parameters in:InputStream the input stream from which bytes will be read.

Method Detail

available back to summary

available	back to summary
public int available() throws IOException Overrides java.io.FilterInputStream.available. Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream. The next invocation might be the same thread or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes. The method returns the sum of the number of bytes that have been pushed back and the value returned by `available`. Returns:int the number of bytes that can be read (or skipped over) from the input stream without blocking. Exceptions IOException: if this input stream has been closed by invoking its `close()` method, or an I/O error occurs. See Also `java.io.FilterInputStream#in`, `java.io.InputStream#available()`

public int available() throws IOException

Overrides java.io.FilterInputStream.available.

Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream. The next invocation might be the same thread or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes.

The method returns the sum of the number of bytes that have been pushed back and the value returned by available.

Returns:int

the number of bytes that can be read (or skipped over) from the input stream without blocking.

Exceptions

IOException:: if this input stream has been closed by invoking its close() method, or an I/O error occurs.

close	back to summary
public synchronized void close() throws IOException Overrides java.io.FilterInputStream.close. Implements java.io.Closeable.close. Closes this input stream and releases any system resources associated with the stream. Once the stream has been closed, further read(), unread(), available(), reset(), or skip() invocations will throw an IOException. Closing a previously closed stream has no effect. Exceptions IOException: if an I/O error occurs.

back to summary

public synchronized void close() throws IOException

Overrides java.io.FilterInputStream.close.

Implements java.io.Closeable.close.

Closes this input stream and releases any system resources associated with the stream. Once the stream has been closed, further read(), unread(), available(), reset(), or skip() invocations will throw an IOException. Closing a previously closed stream has no effect.

Exceptions

IOException:: if an I/O error occurs.

ensureOpen	back to summary
private void ensureOpen() throws IOException Check to make sure that this stream has not been closed

mark back to summary

mark	back to summary
public void mark(int readlimit) Overrides java.io.FilterInputStream.mark. Marks the current position in this input stream. The `mark` method of `PushbackInputStream` does nothing. Parameters readlimit:int the maximum limit of bytes that can be read before the mark position becomes invalid. See Also `java.io.InputStream#reset()`

public void mark(int readlimit)

Overrides java.io.FilterInputStream.mark.

Marks the current position in this input stream.

The mark method of PushbackInputStream does nothing.

Parameters

readlimit:int: the maximum limit of bytes that can be read before the mark position becomes invalid.

See Also

java.io.InputStream#reset()

markSupported back to summary

markSupported	back to summary
public boolean markSupported() Overrides java.io.FilterInputStream.markSupported. Tests if this input stream supports the `mark` and `reset` methods, which it does not. Returns:boolean `false`, since this class does not support the `mark` and `reset` methods. See Also `java.io.InputStream#mark(int)`, `java.io.InputStream#reset()`

public boolean markSupported()

Overrides java.io.FilterInputStream.markSupported.

Tests if this input stream supports the mark and reset methods, which it does not.

Returns:boolean: false, since this class does not support the mark and reset methods.
See Also: java.io.InputStream#mark(int), java.io.InputStream#reset()

read back to summary

read	back to summary
public int read() throws IOException Overrides java.io.FilterInputStream.read. Reads the next byte of data from this input stream. The value byte is returned as an `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. This method returns the most recently pushed-back byte, if there is one, and otherwise calls the `read` method of its underlying input stream and returns whatever value that method returns. Returns:int the next byte of data, or `-1` if the end of the stream has been reached. Exceptions IOException: if this input stream has been closed by invoking its `close()` method, or an I/O error occurs. See Also `java.io.InputStream#read()`

public int read() throws IOException

Overrides java.io.FilterInputStream.read.

Reads the next byte of data from this input stream. The value byte is returned as an 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.

This method returns the most recently pushed-back byte, if there is one, and otherwise calls the read method of its underlying input stream and returns whatever value that method returns.

Returns:int

the next byte of data, or -1 if the end of the stream has been reached.

Exceptions

IOException:: if this input stream has been closed by invoking its close() method, or an I/O error occurs.

See Also

java.io.InputStream#read()

read back to summary

read	back to summary
public int read(byte[] b, int off, int len) throws IOException Overrides java.io.FilterInputStream.read. Reads up to `len` bytes of data from this input stream into an array of bytes. This method first reads any pushed-back bytes; after that, if fewer than `len` bytes have been read then it reads from the underlying input stream. If `len` is not zero, the method blocks until at least 1 byte of input is available; otherwise, no bytes are read and `0` is returned. Parameters b:byte[] the buffer into which the data is read. off:int the start offset in the destination array `b` len:int the maximum number of bytes read. Returns:int the total number of bytes read into the buffer, or `-1` if there is no more data because the end of the stream has been reached. Exceptions IOException: if this input stream has been closed by invoking its `close()` method, or an 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` See Also `java.io.InputStream#read(byte[], int, int)`

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

Overrides java.io.FilterInputStream.read.

Reads up to len bytes of data from this input stream into an array of bytes. This method first reads any pushed-back bytes; after that, if fewer than len bytes have been read then it reads from the underlying input stream. If len is not zero, the method blocks until at least 1 byte of input is available; otherwise, no bytes are read and 0 is returned.

Parameters

b:byte[]: the buffer into which the data is read.
off:int: the start offset in the destination array b
len:int: the maximum number of bytes read.

Returns:int

the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.

Exceptions

IOException:: if this input stream has been closed by invoking its close() method, or an 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

reset back to summary

reset	back to summary
public void reset() throws IOException Overrides java.io.FilterInputStream.reset. Repositions this stream to the position at the time the `mark` method was last called on this input stream. The method `reset` for class `PushbackInputStream` does nothing except throw an `IOException`. Exceptions IOException: if this method is invoked. See Also `java.io.InputStream#mark(int)`, `java.io.IOException`

public void reset() throws IOException

Overrides java.io.FilterInputStream.reset.

Repositions this stream to the position at the time the mark method was last called on this input stream.

The method reset for class PushbackInputStream does nothing except throw an IOException.

Exceptions

IOException:: if this method is invoked.

skip back to summary

skip	back to summary
public long skip(long n) throws IOException Overrides java.io.FilterInputStream.skip. Skips over and discards `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 zero. If `n` is negative, no bytes are skipped. The `skip` method of `PushbackInputStream` first skips over the bytes in the pushback buffer, if any. It then calls the `skip` method of the underlying input stream if more bytes need to be skipped. The actual number of bytes skipped is returned. Exceptions IOException: if the stream has been closed by invoking its `close()` method, `in.skip(n)` throws an IOException, or an I/O error occurs. Since 1.2 See Also `java.io.FilterInputStream#in`, `java.io.InputStream#skip(long n)`

public long skip(long n) throws IOException

Overrides java.io.FilterInputStream.skip.

Skips over and discards 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 zero. If n is negative, no bytes are skipped.

The skip method of PushbackInputStream first skips over the bytes in the pushback buffer, if any. It then calls the skip method of the underlying input stream if more bytes need to be skipped. The actual number of bytes skipped is returned.

Exceptions

IOException:: if the stream has been closed by invoking its close() method, in.skip(n) throws an IOException, or an I/O error occurs.

Since

1.2

transferTo back to summary

transferTo	back to summary
public long transferTo(OutputStream out) throws IOException Overrides java.io.InputStream.transferTo. Doc from java.io.InputStream.transferTo. Reads all bytes from this input stream and writes the bytes to the given output stream in the order that they are read. On return, this input stream will be at end of stream. This method does not close either stream. 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. Annotations @Override Exceptions IOException: if an I/O error occurs when reading or writing

public long transferTo(OutputStream out) throws IOException

Overrides java.io.InputStream.transferTo.

Doc from java.io.InputStream.transferTo.

Reads all bytes from this input stream and writes the bytes to the given output stream in the order that they are read. On return, this input stream will be at end of stream. This method does not close either stream.

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.

Annotations

@Override

Exceptions

IOException:: if an I/O error occurs when reading or writing

unread back to summary

unread	back to summary
public void unread(int b) throws IOException Pushes back a byte by copying it to the front of the pushback buffer. After this method returns, the next byte to be read will have the value `(byte)b`. Parameters b:int the `int` value whose low-order byte is to be pushed back. Exceptions IOException: If there is not enough room in the pushback buffer for the byte, or this input stream has been closed by invoking its `close()` method.

public void unread(int b) throws IOException

Pushes back a byte by copying it to the front of the pushback buffer. After this method returns, the next byte to be read will have the value (byte)b.

Parameters

b:int: the int value whose low-order byte is to be pushed back.

Exceptions

IOException:: If there is not enough room in the pushback buffer for the byte, or this input stream has been closed by invoking its close() method.

unread back to summary

unread	back to summary
public void unread(byte[] b, int off, int len) throws IOException Pushes back a portion of an array of bytes by copying it to the front of the pushback buffer. After this method returns, the next byte to be read will have the value `b[off]`, the byte after that will have the value `b[off+1]`, and so forth. Parameters b:byte[] the byte array to push back. off:int the start offset of the data. len:int the number of bytes to push back. Exceptions IOException: If there is not enough room in the pushback buffer for the specified number of bytes, or this input stream has been closed by invoking its `close()` method. NullPointerException: If `b` is `null`. Since 1.1

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

Pushes back a portion of an array of bytes by copying it to the front of the pushback buffer. After this method returns, the next byte to be read will have the value b[off], the byte after that will have the value b[off+1], and so forth.

Parameters

b:byte[]: the byte array to push back.
off:int: the start offset of the data.
len:int: the number of bytes to push back.

Exceptions

IOException:: If there is not enough room in the pushback buffer for the specified number of bytes, or this input stream has been closed by invoking its close() method.
NullPointerException:: If b is null.

Since

1.1

unread back to summary

unread	back to summary
public void unread(byte[] b) throws IOException Pushes back an array of bytes by copying it to the front of the pushback buffer. After this method returns, the next byte to be read will have the value `b[0]`, the byte after that will have the value `b[1]`, and so forth. Parameters b:byte[] the byte array to push back Exceptions IOException: If there is not enough room in the pushback buffer for the specified number of bytes, or this input stream has been closed by invoking its `close()` method. NullPointerException: If `b` is `null`. Since 1.1

public void unread(byte[] b) throws IOException

Pushes back an array of bytes by copying it to the front of the pushback buffer. After this method returns, the next byte to be read will have the value b[0], the byte after that will have the value b[1], and so forth.

Parameters

b:byte[]: the byte array to push back

Exceptions

IOException:: If there is not enough room in the pushback buffer for the specified number of bytes, or this input stream has been closed by invoking its close() method.
NullPointerException:: If b is null.

Since

1.1

public Class PushbackInputStream

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