https://openjdk.java.net/ 
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package java.io;

import java.nio.charset.Charset;
import java.util.Arrays;
import java.util.Objects;


This class implements an output stream in which the data is written into a byte array. The buffer automatically grows as data is written to it. The data can be retrieved using toByteArray() and toString(). 
 Closing a ByteArrayOutputStream has no effect. The methods in this class can be called after the stream has been closed without generating an IOException. 
Author: Arthur van Hoff
Since:  1.0
/**
 * This class implements an output stream in which the data is
 * written into a byte array. The buffer automatically grows as data
 * is written to it.
 * The data can be retrieved using {@code toByteArray()} and
 * {@code toString()}.
 * <p>
 * Closing a {@code ByteArrayOutputStream} has no effect. The methods in
 * this class can be called after the stream has been closed without
 * generating an {@code IOException}.
 *
 * @author  Arthur van Hoff
 * @since   1.0
 */

public class ByteArrayOutputStream extends OutputStream {

    
The buffer where data is stored.

/**
     * The buffer where data is stored.
     */
    protected byte buf[];

    
The number of valid bytes in the buffer.

/**
     * The number of valid bytes in the buffer.
     */
    protected int count;

    
Creates a new ByteArrayOutputStream. The buffer capacity is initially 32 bytes, though its size increases if necessary. 
/**
     * Creates a new {@code ByteArrayOutputStream}. The buffer capacity is
     * initially 32 bytes, though its size increases if necessary.
     */
    public ByteArrayOutputStream() {
        this(32);
    }

    
Creates a new ByteArrayOutputStream, with a buffer capacity of the specified size, in bytes. 
Params:
  • size –   the initial size.
Throws:
/**
     * Creates a new {@code ByteArrayOutputStream}, with a buffer capacity of
     * the specified size, in bytes.
     *
     * @param  size   the initial size.
     * @throws IllegalArgumentException if size is negative.
     */
    public ByteArrayOutputStream(int size) {
        if (size < 0) {
            throw new IllegalArgumentException("Negative initial size: "
                                               + size);
        }
        buf = new byte[size];
    }

    
Increases the capacity if necessary to ensure that it can hold
at least the number of elements specified by the minimum
capacity argument.

Params:
  • minCapacity – the desired minimum capacity
Throws:
  • OutOfMemoryError – if minCapacity < 0. This is interpreted as a request for the unsatisfiably large capacity (long) Integer.MAX_VALUE + (minCapacity - Integer.MAX_VALUE).
/**
     * Increases the capacity if necessary to ensure that it can hold
     * at least the number of elements specified by the minimum
     * capacity argument.
     *
     * @param  minCapacity the desired minimum capacity
     * @throws OutOfMemoryError if {@code minCapacity < 0}.  This is
     * interpreted as a request for the unsatisfiably large capacity
     * {@code (long) Integer.MAX_VALUE + (minCapacity - Integer.MAX_VALUE)}.
     */
    private void ensureCapacity(int minCapacity) {
        // overflow-conscious code
        if (minCapacity - buf.length > 0)
            grow(minCapacity);
    }

    
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_ARRAY_SIZE = Integer.MAX_VALUE - 8;

    
Increases the capacity to ensure that it can hold at least the
number of elements specified by the minimum capacity argument.

Params:
  • minCapacity – the desired minimum capacity
/**
     * Increases the capacity to ensure that it can hold at least the
     * number of elements specified by the minimum capacity argument.
     *
     * @param minCapacity the desired minimum capacity
     */
    private void grow(int minCapacity) {
        // overflow-conscious code
        int oldCapacity = buf.length;
        int newCapacity = oldCapacity << 1;
        if (newCapacity - minCapacity < 0)
            newCapacity = minCapacity;
        if (newCapacity - MAX_ARRAY_SIZE > 0)
            newCapacity = hugeCapacity(minCapacity);
        buf = Arrays.copyOf(buf, newCapacity);
    }

    private static int hugeCapacity(int minCapacity) {
        if (minCapacity < 0) // overflow
            throw new OutOfMemoryError();
        return (minCapacity > MAX_ARRAY_SIZE) ?
            Integer.MAX_VALUE :
            MAX_ARRAY_SIZE;
    }

    
Writes the specified byte to this ByteArrayOutputStream. 
Params:
  • b –   the byte to be written.
/**
     * Writes the specified byte to this {@code ByteArrayOutputStream}.
     *
     * @param   b   the byte to be written.
     */
    public synchronized void write(int b) {
        ensureCapacity(count + 1);
        buf[count] = (byte) b;
        count += 1;
    }

    
Writes len bytes from the specified byte array starting at offset off to this ByteArrayOutputStream. 
Params:
  • b –     the data.
  • off –   the start offset in the data.
  • len –   the number of bytes to write.
Throws:
/**
     * Writes {@code len} bytes from the specified byte array
     * starting at offset {@code off} to this {@code ByteArrayOutputStream}.
     *
     * @param   b     the data.
     * @param   off   the start offset in the data.
     * @param   len   the number of bytes to write.
     * @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}
     */
    public synchronized void write(byte b[], int off, int len) {
        Objects.checkFromIndexSize(off, len, b.length);
        ensureCapacity(count + len);
        System.arraycopy(b, off, buf, count, len);
        count += len;
    }

    
Writes the complete contents of the specified byte array to this ByteArrayOutputStream. 
Params:
  • b –     the data.
Throws:
API Note: This method is equivalent to 
write(b, 0, b.length).
Since:  11
/**
     * Writes the complete contents of the specified byte array
     * to this {@code ByteArrayOutputStream}.
     *
     * @apiNote
     * This method is equivalent to {@link #write(byte[],int,int)
     * write(b, 0, b.length)}.
     *
     * @param   b     the data.
     * @throws  NullPointerException if {@code b} is {@code null}.
     * @since   11
     */
    public void writeBytes(byte b[]) {
        write(b, 0, b.length);
    }

    
Writes the complete contents of this ByteArrayOutputStream to the specified output stream argument, as if by calling the output stream's write method using out.write(buf, 0, count). 
Params:
  • out –   the output stream to which to write the data.
Throws:
/**
     * Writes the complete contents of this {@code ByteArrayOutputStream} to
     * the specified output stream argument, as if by calling the output
     * stream's write method using {@code out.write(buf, 0, count)}.
     *
     * @param   out   the output stream to which to write the data.
     * @throws  NullPointerException if {@code out} is {@code null}.
     * @throws  IOException if an I/O error occurs.
     */
    public synchronized void writeTo(OutputStream out) throws IOException {
        out.write(buf, 0, count);
    }

    
Resets the count field of this ByteArrayOutputStream to zero, so that all currently accumulated output in the output stream is discarded. The output stream can be used again, reusing the already allocated buffer space. 
See Also:
/**
     * Resets the {@code count} field of this {@code ByteArrayOutputStream}
     * to zero, so that all currently accumulated output in the
     * output stream is discarded. The output stream can be used again,
     * reusing the already allocated buffer space.
     *
     * @see     java.io.ByteArrayInputStream#count
     */
    public synchronized void reset() {
        count = 0;
    }

    
Creates a newly allocated byte array. Its size is the current
size of this output stream and the valid contents of the buffer
have been copied into it.

See Also:
Returns: the current contents of this output stream, as a byte array.
/**
     * Creates a newly allocated byte array. Its size is the current
     * size of this output stream and the valid contents of the buffer
     * have been copied into it.
     *
     * @return  the current contents of this output stream, as a byte array.
     * @see     java.io.ByteArrayOutputStream#size()
     */
    public synchronized byte[] toByteArray() {
        return Arrays.copyOf(buf, count);
    }

    
Returns the current size of the buffer.

See Also:
Returns: the value of the count field, which is the number of valid bytes in this output stream.
/**
     * Returns the current size of the buffer.
     *
     * @return  the value of the {@code count} field, which is the number
     *          of valid bytes in this output stream.
     * @see     java.io.ByteArrayOutputStream#count
     */
    public synchronized int size() {
        return count;
    }

    
Converts the buffer's contents into a string decoding bytes using the platform's default character set. The length of the new String is a function of the character set, and hence may not be equal to the size of the buffer. 
 This method always replaces malformed-input and unmappable-character sequences with the default replacement string for the platform's default character set. The CharsetDecoder class should be used when more control over the decoding process is required. 
Returns:String decoded from the buffer's contents.
Since: 1.1
/**
     * Converts the buffer's contents into a string decoding bytes using the
     * platform's default character set. The length of the new {@code String}
     * is a function of the character set, and hence may not be equal to the
     * size of the buffer.
     *
     * <p> This method always replaces malformed-input and unmappable-character
     * sequences with the default replacement string for the platform's
     * default character set. The {@linkplain java.nio.charset.CharsetDecoder}
     * class should be used when more control over the decoding process is
     * required.
     *
     * @return String decoded from the buffer's contents.
     * @since  1.1
     */
    public synchronized String toString() {
        return new String(buf, 0, count);
    }

    
Converts the buffer's contents into a string by decoding the bytes using the named charset. 
 This method is equivalent to #toString(charset) that takes a charset. 
 An invocation of this method of the form

 
     ByteArrayOutputStream b = ...
     b.toString("UTF-8")
      

behaves in exactly the same way as the expression

 
     ByteArrayOutputStream b = ...
     b.toString(StandardCharsets.UTF_8)
      


Params:
  • charsetName –  the name of a supported charset
Throws:
Returns:String decoded from the buffer's contents.
Since: 1.1
/**
     * Converts the buffer's contents into a string by decoding the bytes using
     * the named {@link java.nio.charset.Charset charset}.
     *
     * <p> This method is equivalent to {@code #toString(charset)} that takes a
     * {@link java.nio.charset.Charset charset}.
     *
     * <p> An invocation of this method of the form
     *
     * <pre> {@code
     *      ByteArrayOutputStream b = ...
     *      b.toString("UTF-8")
     *      }
     * </pre>
     *
     * behaves in exactly the same way as the expression
     *
     * <pre> {@code
     *      ByteArrayOutputStream b = ...
     *      b.toString(StandardCharsets.UTF_8)
     *      }
     * </pre>
     *
     *
     * @param  charsetName  the name of a supported
     *         {@link java.nio.charset.Charset charset}
     * @return String decoded from the buffer's contents.
     * @throws UnsupportedEncodingException
     *         If the named charset is not supported
     * @since  1.1
     */
    public synchronized String toString(String charsetName)
        throws UnsupportedEncodingException
    {
        return new String(buf, 0, count, charsetName);
    }

    
Converts the buffer's contents into a string by decoding the bytes using the specified charset. The length of the new String is a function of the charset, and hence may not be equal to the length of the byte array. 
 This method always replaces malformed-input and unmappable-character sequences with the charset's default replacement string. The CharsetDecoder class should be used when more control over the decoding process is required. 
Params:
  • charset –  the charset to be used to decode the bytes
Returns:    String decoded from the buffer's contents.
Since:     10
/**
     * Converts the buffer's contents into a string by decoding the bytes using
     * the specified {@link java.nio.charset.Charset charset}. The length of the new
     * {@code String} is a function of the charset, and hence may not be equal
     * to the length of the byte array.
     *
     * <p> This method always replaces malformed-input and unmappable-character
     * sequences with the charset's default replacement string. The {@link
     * java.nio.charset.CharsetDecoder} class should be used when more control
     * over the decoding process is required.
     *
     * @param      charset  the {@linkplain java.nio.charset.Charset charset}
     *             to be used to decode the {@code bytes}
     * @return     String decoded from the buffer's contents.
     * @since      10
     */
    public synchronized String toString(Charset charset) {
        return new String(buf, 0, count, charset);
    }

    
Creates a newly allocated string. Its size is the current size of
the output stream and the valid contents of the buffer have been
copied into it. Each character c in the resulting string is
constructed from the corresponding element b in the byte
array such that:


    c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))



Params:
  • hibyte –    the high byte of each resulting Unicode character.
See Also:
Deprecated:This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via the toString(String charsetName) or toString(Charset charset) method, which takes an encoding-name or charset argument, or the toString() method, which uses the platform's default character encoding.
Returns:    the current contents of the output stream, as a string.
/**
     * Creates a newly allocated string. Its size is the current size of
     * the output stream and the valid contents of the buffer have been
     * copied into it. Each character <i>c</i> in the resulting string is
     * constructed from the corresponding element <i>b</i> in the byte
     * array such that:
     * <blockquote><pre>{@code
     *     c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
     * }</pre></blockquote>
     *
     * @deprecated This method does not properly convert bytes into characters.
     * As of JDK&nbsp;1.1, the preferred way to do this is via the
     * {@link #toString(String charsetName)} or {@link #toString(Charset charset)}
     * method, which takes an encoding-name or charset argument,
     * or the {@code toString()} method, which uses the platform's default
     * character encoding.
     *
     * @param      hibyte    the high byte of each resulting Unicode character.
     * @return     the current contents of the output stream, as a string.
     * @see        java.io.ByteArrayOutputStream#size()
     * @see        java.io.ByteArrayOutputStream#toString(String)
     * @see        java.io.ByteArrayOutputStream#toString()
     */
    @Deprecated
    public synchronized String toString(int hibyte) {
        return new String(buf, hibyte, 0, count);
    }

    
Closing a ByteArrayOutputStream has no effect. The methods in this class can be called after the stream has been closed without generating an IOException. 
/**
     * Closing a {@code ByteArrayOutputStream} has no effect. The methods in
     * this class can be called after the stream has been closed without
     * generating an {@code IOException}.
     */
    public void close() throws IOException {
    }

}