https://openjdk.java.net/ 
/*
 * Copyright (c) 1994, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * questions.
 */

package java.io;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;


This abstract class is the superclass of all classes representing
an input stream of bytes.

 Applications that need to define a subclass of InputStream
must always provide a method that returns the next byte of input.

Author: Arthur van Hoff
See Also:
Since:  1.0
/**
 * This abstract class is the superclass of all classes representing
 * an input stream of bytes.
 *
 * <p> Applications that need to define a subclass of <code>InputStream</code>
 * must always provide a method that returns the next byte of input.
 *
 * @author  Arthur van Hoff
 * @see     java.io.BufferedInputStream
 * @see     java.io.ByteArrayInputStream
 * @see     java.io.DataInputStream
 * @see     java.io.FilterInputStream
 * @see     java.io.InputStream#read()
 * @see     java.io.OutputStream
 * @see     java.io.PushbackInputStream
 * @since   1.0
 */
public abstract class InputStream implements Closeable {

    // MAX_SKIP_BUFFER_SIZE is used to determine the maximum buffer size to
    // use when skipping.
    private static final int MAX_SKIP_BUFFER_SIZE = 2048;

    private static final int DEFAULT_BUFFER_SIZE = 8192;

    
Returns a new 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), 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. 
Returns:an InputStream which contains no bytes
Since:11
/**
     * Returns a new {@code InputStream} that reads no bytes. The returned
     * stream is initially open.  The stream is closed by calling the
     * {@code close()} method.  Subsequent calls to {@code close()} have no
     * effect.
     *
     * <p> While the stream is open, the {@code available()}, {@code read()},
     * {@code read(byte[])}, {@code read(byte[], int, int)},
     * {@code readAllBytes()}, {@code readNBytes(byte[], int, int)},
     * {@code readNBytes(int)}, {@code skip(long)}, and
     * {@code transferTo()} methods all behave as if end of stream has been
     * reached.  After the stream has been closed, these methods all throw
     * {@code IOException}.
     *
     * <p> The {@code markSupported()} method returns {@code false}.  The
     * {@code mark()} method does nothing, and the {@code reset()} method
     * throws {@code IOException}.
     *
     * @return an {@code InputStream} which contains no bytes
     *
     * @since 11
     */
    public static InputStream nullInputStream() {
        return new InputStream() {
            private volatile boolean closed;

            private void ensureOpen() throws IOException {
                if (closed) {
                    throw new IOException("Stream closed");
                }
            }

            @Override
            public int available () throws IOException {
                ensureOpen();
                return 0;
            }

            @Override
            public int read() throws IOException {
                ensureOpen();
                return -1;
            }

            @Override
            public int read(byte[] b, int off, int len) throws IOException {
                Objects.checkFromIndexSize(off, len, b.length);
                if (len == 0) {
                    return 0;
                }
                ensureOpen();
                return -1;
            }

            @Override
            public byte[] readAllBytes() throws IOException {
                ensureOpen();
                return new byte[0];
            }

            @Override
            public int readNBytes(byte[] b, int off, int len)
                throws IOException {
                Objects.checkFromIndexSize(off, len, b.length);
                ensureOpen();
                return 0;
            }

            @Override
            public byte[] readNBytes(int len) throws IOException {
                if (len < 0) {
                    throw new IllegalArgumentException("len < 0");
                }
                ensureOpen();
                return new byte[0];
            }

            @Override
            public long skip(long n) throws IOException {
                ensureOpen();
                return 0L;
            }

            @Override
            public long transferTo(OutputStream out) throws IOException {
                Objects.requireNonNull(out);
                ensureOpen();
                return 0L;
            }

            @Override
            public void close() throws IOException {
                closed = true;
            }
        };
    }

    
Reads the next byte of data from the 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.

 A subclass must provide an implementation of this method.

Throws:
Returns:    the next byte of data, or -1 if the end of the
            stream is reached.
/**
     * Reads the next byte of data from the input stream. The value byte is
     * returned as an <code>int</code> in the range <code>0</code> to
     * <code>255</code>. If no byte is available because the end of the stream
     * has been reached, the value <code>-1</code> is returned. This method
     * blocks until input data is available, the end of the stream is detected,
     * or an exception is thrown.
     *
     * <p> A subclass must provide an implementation of this method.
     *
     * @return     the next byte of data, or <code>-1</code> if the end of the
     *             stream is reached.
     * @exception  IOException  if an I/O error occurs.
     */
    public abstract int read() throws IOException;

    
Reads some number of bytes from the input stream and stores them into
the buffer array 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.

 The read(b) method for class InputStream
has the same effect as: 
 read(b, 0, b.length) 


Params:
  • b –   the buffer into which the data is read.
Throws:
  • 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.
See Also:
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.
/**
     * Reads some number of bytes from the input stream and stores them into
     * the buffer array <code>b</code>. 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.
     *
     * <p> If the length of <code>b</code> is zero, then no bytes are read and
     * <code>0</code> 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 <code>-1</code> is returned; otherwise, at
     * least one byte is read and stored into <code>b</code>.
     *
     * <p> The first byte read is stored into element <code>b[0]</code>, the
     * next one into <code>b[1]</code>, and so on. The number of bytes read is,
     * at most, equal to the length of <code>b</code>. Let <i>k</i> be the
     * number of bytes actually read; these bytes will be stored in elements
     * <code>b[0]</code> through <code>b[</code><i>k</i><code>-1]</code>,
     * leaving elements <code>b[</code><i>k</i><code>]</code> through
     * <code>b[b.length-1]</code> unaffected.
     *
     * <p> The <code>read(b)</code> method for class <code>InputStream</code>
     * has the same effect as: <pre><code> read(b, 0, b.length) </code></pre>
     *
     * @param      b   the buffer into which the data is read.
     * @return     the total number of bytes read into the buffer, or
     *             <code>-1</code> if there is no more data because the end of
     *             the stream has been reached.
     * @exception  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.
     * @exception  NullPointerException  if <code>b</code> is <code>null</code>.
     * @see        java.io.InputStream#read(byte[], int, int)
     */
    public int read(byte b[]) throws IOException {
        return read(b, 0, b.length);
    }

    
Reads up to 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] and elements b[off+len] through
b[b.length-1] are unaffected.

 The 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.

Params:
  • 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.
Throws:
  • 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
See Also:
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.
/**
     * Reads up to <code>len</code> bytes of data from the input stream into
     * an array of bytes.  An attempt is made to read as many as
     * <code>len</code> bytes, but a smaller number may be read.
     * The number of bytes actually read is returned as an integer.
     *
     * <p> This method blocks until input data is available, end of file is
     * detected, or an exception is thrown.
     *
     * <p> If <code>len</code> is zero, then no bytes are read and
     * <code>0</code> 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 <code>-1</code> is returned; otherwise, at least one
     * byte is read and stored into <code>b</code>.
     *
     * <p> The first byte read is stored into element <code>b[off]</code>, the
     * next one into <code>b[off+1]</code>, and so on. The number of bytes read
     * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of
     * bytes actually read; these bytes will be stored in elements
     * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,
     * leaving elements <code>b[off+</code><i>k</i><code>]</code> through
     * <code>b[off+len-1]</code> unaffected.
     *
     * <p> In every case, elements <code>b[0]</code> through
     * <code>b[off]</code> and elements <code>b[off+len]</code> through
     * <code>b[b.length-1]</code> are unaffected.
     *
     * <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method
     * for class <code>InputStream</code> simply calls the method
     * <code>read()</code> repeatedly. If the first such call results in an
     * <code>IOException</code>, that exception is returned from the call to
     * the <code>read(b,</code> <code>off,</code> <code>len)</code> method.  If
     * any subsequent call to <code>read()</code> results in a
     * <code>IOException</code>, the exception is caught and treated as if it
     * were end of file; the bytes read up to that point are stored into
     * <code>b</code> 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 <code>len</code> 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.
     *
     * @param      b     the buffer into which the data is read.
     * @param      off   the start offset in array <code>b</code>
     *                   at which the data is written.
     * @param      len   the maximum number of bytes to read.
     * @return     the total number of bytes read into the buffer, or
     *             <code>-1</code> if there is no more data because the end of
     *             the stream has been reached.
     * @exception  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.
     * @exception  NullPointerException If <code>b</code> is <code>null</code>.
     * @exception  IndexOutOfBoundsException If <code>off</code> is negative,
     * <code>len</code> is negative, or <code>len</code> is greater than
     * <code>b.length - off</code>
     * @see        java.io.InputStream#read()
     */
    public int read(byte b[], int off, int len) throws IOException {
        Objects.checkFromIndexSize(off, len, b.length);
        if (len == 0) {
            return 0;
        }

        int c = read();
        if (c == -1) {
            return -1;
        }
        b[off] = (byte)c;

        int i = 1;
        try {
            for (; i < len ; i++) {
                c = read();
                if (c == -1) {
                    break;
                }
                b[off + i] = (byte)c;
            }
        } catch (IOException ee) {
        }
        return i;
    }

    
The maximum size of array to allocate.
Some VMs reserve some header words in an array.
Attempts to allocate larger arrays may result in
OutOfMemoryError: Requested array size exceeds VM limit

/**
     * The maximum size of array to allocate.
     * Some VMs reserve some header words in an array.
     * Attempts to allocate larger arrays may result in
     * OutOfMemoryError: Requested array size exceeds VM limit
     */
    private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;

    
Reads all remaining bytes from the input stream. This method blocks until
all remaining bytes have been read and end of stream is detected, or an
exception is thrown. This method does not close the input stream.

 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.

Throws:
Implementation Requirements: This method invokes readNBytes(int) with a length of Integer.MAX_VALUE.
Returns:a byte array containing the bytes read from this input stream
Since:9
/**
     * Reads all remaining bytes from the input stream. This method blocks until
     * all remaining bytes have been read and end of stream is detected, or an
     * exception is thrown. This method does not close the input stream.
     *
     * <p> When this stream reaches end of stream, further invocations of this
     * method will return an empty byte array.
     *
     * <p> 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.
     *
     * <p> The behavior for the case where the input stream is <i>asynchronously
     * closed</i>, or the thread interrupted during the read, is highly input
     * stream specific, and therefore not specified.
     *
     * <p> 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.
     *
     * @implSpec
     * This method invokes {@link #readNBytes(int)} with a length of
     * {@link Integer#MAX_VALUE}.
     *
     * @return a byte array containing the bytes read from this input stream
     * @throws IOException if an I/O error occurs
     * @throws OutOfMemoryError if an array of the required size cannot be
     *         allocated.
     *
     * @since 9
     */
    public byte[] readAllBytes() throws IOException {
        return readNBytes(Integer.MAX_VALUE);
    }

    
Reads up to a specified number of bytes from the input stream. This
method blocks until the requested number of bytes have been read, end
of stream is detected, or an exception is thrown. This method does not
close the input stream.

 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.

Params:
  • len – the maximum number of bytes to read
Throws:
Implementation Note: The number of bytes allocated to read data from this stream and return the result is bounded by 2*(long)len, inclusive.
Returns:a byte array containing the bytes read from this input stream
Since:11
/**
     * Reads up to a specified number of bytes from the input stream. This
     * method blocks until the requested number of bytes have been read, end
     * of stream is detected, or an exception is thrown. This method does not
     * close the input stream.
     *
     * <p> The length of the returned array equals the number of bytes read
     * from the stream. If {@code len} is zero, then no bytes are read and
     * an empty byte array is returned. Otherwise, up to {@code len} bytes
     * are read from the stream. Fewer than {@code len} bytes may be read if
     * end of stream is encountered.
     *
     * <p> When this stream reaches end of stream, further invocations of this
     * method will return an empty byte array.
     *
     * <p> 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 {@code len}.
     * Therefore, the method may be safely called with very large values of
     * {@code len} provided sufficient memory is available.
     *
     * <p> The behavior for the case where the input stream is <i>asynchronously
     * closed</i>, or the thread interrupted during the read, is highly input
     * stream specific, and therefore not specified.
     *
     * <p> 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.
     *
     * @implNote
     * The number of bytes allocated to read data from this stream and return
     * the result is bounded by {@code 2*(long)len}, inclusive.
     *
     * @param len the maximum number of bytes to read
     * @return a byte array containing the bytes read from this input stream
     * @throws IllegalArgumentException if {@code length} is negative
     * @throws IOException if an I/O error occurs
     * @throws OutOfMemoryError if an array of the required size cannot be
     *         allocated.
     *
     * @since 11
     */
    public byte[] readNBytes(int len) throws IOException {
        if (len < 0) {
            throw new IllegalArgumentException("len < 0");
        }

        List<byte[]> bufs = null;
        byte[] result = null;
        int total = 0;
        int remaining = len;
        int n;
        do {
            byte[] buf = new byte[Math.min(remaining, DEFAULT_BUFFER_SIZE)];
            int nread = 0;

            // read to EOF which may read more or less than buffer size
            while ((n = read(buf, nread,
                    Math.min(buf.length - nread, remaining))) > 0) {
                nread += n;
                remaining -= n;
            }

            if (nread > 0) {
                if (MAX_BUFFER_SIZE - total < nread) {
                    throw new OutOfMemoryError("Required array size too large");
                }
                total += nread;
                if (result == null) {
                    result = buf;
                } else {
                    if (bufs == null) {
                        bufs = new ArrayList<>();
                        bufs.add(result);
                    }
                    bufs.add(buf);
                }
            }
            // if the last call to read returned -1 or the number of bytes
            // requested have been read then break
        } while (n >= 0 && remaining > 0);

        if (bufs == null) {
            if (result == null) {
                return new byte[0];
            }
            return result.length == total ?
                result : Arrays.copyOf(result, total);
        }

        result = new byte[total];
        int offset = 0;
        remaining = total;
        for (byte[] b : bufs) {
            int count = Math.min(b.length, remaining);
            System.arraycopy(b, 0, result, offset, count);
            offset += count;
            remaining -= count;
        }

        return result;
    }

    
Reads the requested number of bytes from the input stream into the given byte array. This method blocks until 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. 
Params:
  • b – the byte array into which the data is read
  • off – the start offset in b at which the data is written
  • len – the maximum number of bytes to read
Throws:
Returns:the actual number of bytes read into the buffer
Since:9
/**
     * Reads the requested number of bytes from the input stream into the given
     * byte array. This method blocks until {@code 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.
     *
     * <p> In the case where end of stream is reached before {@code 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.
     *
     * <p> If {@code len} is zero, then no bytes are read and {@code 0} is
     * returned; otherwise, there is an attempt to read up to {@code len} bytes.
     *
     * <p> The first byte read is stored into element {@code b[off]}, the next
     * one in to {@code b[off+1]}, and so on. The number of bytes read is, at
     * most, equal to {@code len}. Let <i>k</i> be the number of bytes actually
     * read; these bytes will be stored in elements {@code b[off]} through
     * {@code b[off+}<i>k</i>{@code -1]}, leaving elements {@code b[off+}<i>k</i>
     * {@code ]} through {@code b[off+len-1]} unaffected.
     *
     * <p> The behavior for the case where the input stream is <i>asynchronously
     * closed</i>, or the thread interrupted during the read, is highly input
     * stream specific, and therefore not specified.
     *
     * <p> If an I/O error occurs reading from the input stream, then it may do
     * so after some, but not all, bytes of {@code b} have been updated with
     * data from the input stream. Consequently the input stream and {@code b}
     * may be in an inconsistent state. It is strongly recommended that the
     * stream be promptly closed if an I/O error occurs.
     *
     * @param  b the byte array into which the data is read
     * @param  off the start offset in {@code b} at which the data is written
     * @param  len the maximum number of bytes to read
     * @return the actual number of bytes read into the buffer
     * @throws IOException if an I/O error occurs
     * @throws NullPointerException if {@code b} is {@code null}
     * @throws IndexOutOfBoundsException If {@code off} is negative, {@code len}
     *         is negative, or {@code len} is greater than {@code b.length - off}
     *
     * @since 9
     */
    public int readNBytes(byte[] b, int off, int len) throws IOException {
        Objects.checkFromIndexSize(off, len, b.length);

        int n = 0;
        while (n < len) {
            int count = read(b, off + n, len - n);
            if (count < 0)
                break;
            n += count;
        }
        return n;
    }

    
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 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. 
 The 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.

Params:
  • n –   the number of bytes to be skipped.
Throws:
Returns:    the actual number of bytes skipped.
/**
     * Skips over and discards <code>n</code> bytes of data from this input
     * stream. The <code>skip</code> method may, for a variety of reasons, end
     * up skipping over some smaller number of bytes, possibly <code>0</code>.
     * This may result from any of a number of conditions; reaching end of file
     * before <code>n</code> bytes have been skipped is only one possibility.
     * The actual number of bytes skipped is returned. If {@code n} is
     * negative, the {@code skip} method for class {@code InputStream} always
     * returns 0, and no bytes are skipped. Subclasses may handle the negative
     * value differently.
     *
     * <p> The <code>skip</code> method implementation of this class creates a
     * byte array and then repeatedly reads into it until <code>n</code> 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.
     *
     * @param      n   the number of bytes to be skipped.
     * @return     the actual number of bytes skipped.
     * @throws     IOException  if an I/O error occurs.
     */
    public long skip(long n) throws IOException {

        long remaining = n;
        int nr;

        if (n <= 0) {
            return 0;
        }

        int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining);
        byte[] skipBuffer = new byte[size];
        while (remaining > 0) {
            nr = read(skipBuffer, 0, (int)Math.min(size, remaining));
            if (nr < 0) {
                break;
            }
            remaining -= nr;
        }

        return n - remaining;
    }

    
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.  The read might be on 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.

 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. 
 The available method of InputStream always returns 0. 
 This method should be overridden by subclasses.

Throws:
Returns: an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking or 0 when it reaches the end of the input stream.
/**
     * 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.  The read might be on 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.
     *
     * <p> Note that while some implementations of {@code 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.
     *
     * <p> A subclass's implementation of this method may choose to throw an
     * {@link IOException} if this input stream has been closed by invoking the
     * {@link #close()} method.
     *
     * <p> The {@code available} method of {@code InputStream} always returns
     * {@code 0}.
     *
     * <p> This method should be overridden by subclasses.
     *
     * @return     an estimate of the number of bytes that can be read (or
     *             skipped over) from this input stream without blocking or
     *             {@code 0} when it reaches the end of the input stream.
     * @exception  IOException if an I/O error occurs.
     */
    public int available() throws IOException {
        return 0;
    }

    
Closes this input stream and releases any system resources associated
with the stream.

 The close method of InputStream does
nothing.

Throws:
  • IOException –  if an I/O error occurs.
/**
     * Closes this input stream and releases any system resources associated
     * with the stream.
     *
     * <p> The <code>close</code> method of <code>InputStream</code> does
     * nothing.
     *
     * @exception  IOException  if an I/O error occurs.
     */
    public void close() throws IOException {}

    
Marks the current position in this input stream. A subsequent call to
the 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.

 The mark method of InputStream does
nothing.

Params:
  • readlimit –   the maximum limit of bytes that can be read before
                     the mark position becomes invalid.
See Also:
/**
     * Marks the current position in this input stream. A subsequent call to
     * the <code>reset</code> method repositions this stream at the last marked
     * position so that subsequent reads re-read the same bytes.
     *
     * <p> The <code>readlimit</code> arguments tells this input stream to
     * allow that many bytes to be read before the mark position gets
     * invalidated.
     *
     * <p> The general contract of <code>mark</code> is that, if the method
     * <code>markSupported</code> returns <code>true</code>, the stream somehow
     * remembers all the bytes read after the call to <code>mark</code> and
     * stands ready to supply those same bytes again if and whenever the method
     * <code>reset</code> is called.  However, the stream is not required to
     * remember any data at all if more than <code>readlimit</code> bytes are
     * read from the stream before <code>reset</code> is called.
     *
     * <p> Marking a closed stream should not have any effect on the stream.
     *
     * <p> The <code>mark</code> method of <code>InputStream</code> does
     * nothing.
     *
     * @param   readlimit   the maximum limit of bytes that can be read before
     *                      the mark position becomes invalid.
     * @see     java.io.InputStream#reset()
     */
    public synchronized void mark(int readlimit) {}

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

 The general contract of reset is:

    

  •  If the method markSupported returns
true, then:
    
    •  If the method 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.
    
    •  If such an 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. 
    

  •  If the method markSupported returns
false, then:
    
    •  The call to reset may throw an
    IOException.
    
    •  If an 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. 


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

Throws:
  • IOException –  if this stream has not been marked or if the
              mark has been invalidated.
See Also:
/**
     * Repositions this stream to the position at the time the
     * <code>mark</code> method was last called on this input stream.
     *
     * <p> The general contract of <code>reset</code> is:
     *
     * <ul>
     * <li> If the method <code>markSupported</code> returns
     * <code>true</code>, then:
     *
     *     <ul><li> If the method <code>mark</code> has not been called since
     *     the stream was created, or the number of bytes read from the stream
     *     since <code>mark</code> was last called is larger than the argument
     *     to <code>mark</code> at that last call, then an
     *     <code>IOException</code> might be thrown.
     *
     *     <li> If such an <code>IOException</code> is not thrown, then the
     *     stream is reset to a state such that all the bytes read since the
     *     most recent call to <code>mark</code> (or since the start of the
     *     file, if <code>mark</code> has not been called) will be resupplied
     *     to subsequent callers of the <code>read</code> method, followed by
     *     any bytes that otherwise would have been the next input data as of
     *     the time of the call to <code>reset</code>. </ul>
     *
     * <li> If the method <code>markSupported</code> returns
     * <code>false</code>, then:
     *
     *     <ul><li> The call to <code>reset</code> may throw an
     *     <code>IOException</code>.
     *
     *     <li> If an <code>IOException</code> 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 <code>read</code> method depend on the
     *     particular type of the input stream. </ul></ul>
     *
     * <p>The method <code>reset</code> for class <code>InputStream</code>
     * does nothing except throw an <code>IOException</code>.
     *
     * @exception  IOException  if this stream has not been marked or if the
     *               mark has been invalidated.
     * @see     java.io.InputStream#mark(int)
     * @see     java.io.IOException
     */
    public synchronized void reset() throws IOException {
        throw new IOException("mark/reset not supported");
    }

    
Tests if this input stream supports the mark and
reset methods. Whether or not mark and
reset are supported is an invariant property of a
particular input stream instance. The markSupported method
of InputStream returns false.

See Also:
Returns: true if this stream instance supports the mark
         and reset methods; false otherwise.
/**
     * Tests if this input stream supports the <code>mark</code> and
     * <code>reset</code> methods. Whether or not <code>mark</code> and
     * <code>reset</code> are supported is an invariant property of a
     * particular input stream instance. The <code>markSupported</code> method
     * of <code>InputStream</code> returns <code>false</code>.
     *
     * @return  <code>true</code> if this stream instance supports the mark
     *          and reset methods; <code>false</code> otherwise.
     * @see     java.io.InputStream#mark(int)
     * @see     java.io.InputStream#reset()
     */
    public boolean markSupported() {
        return false;
    }

    
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 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.

Params:
  • out – the output stream, non-null
Throws:
Returns:the number of bytes transferred
Since:9
/**
     * 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.
     * <p>
     * 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 <i>asynchronously closed</i>, or the thread
     * interrupted during the transfer, is highly input and output stream
     * specific, and therefore not specified.
     * <p>
     * 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.
     *
     * @param  out the output stream, non-null
     * @return the number of bytes transferred
     * @throws IOException if an I/O error occurs when reading or writing
     * @throws NullPointerException if {@code out} is {@code null}
     *
     * @since 9
     */
    public long transferTo(OutputStream out) throws IOException {
        Objects.requireNonNull(out, "out");
        long transferred = 0;
        byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
        int read;
        while ((read = this.read(buffer, 0, DEFAULT_BUFFER_SIZE)) >= 0) {
            out.write(buffer, 0, read);
            transferred += read;
        }
        return transferred;
    }
}