[Chapter 11] ByteArrayOutputStream

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| Chapter 11 The java.io Package |

# ByteArrayOutputStream

## Name

ByteArrayOutputStream

## Synopsis

Class Name:

  `java.io.ByteArrayOutputStream`

Superclass:

  `java.io.FilterOutputStream`

Immediate Subclasses:

  None

Interfaces Implemented:

  None

Availability:

  JDK 1.0 or later

## Description

A `ByteArrayOutputStream` is a stream whose data is written to an internal byte array. None of the methods of this class throws an `IOException` because the data is written to an array instead of an actual I/O device.

The data for a `ByteArrayOutputStream` can be sent to another `OutputStream` using the `writeTo()` method. A copy of the array can be obtained using the `toCharArray()` method.

## Class Summary

    public class java.io.ByteArrayOutputStream extends java.io.OutputStream {
      // Variables
      protected byte[] buf;
      protected int count;

      // Constructors
      public ByteArrayOutputStream();
      public ByteArrayOutputStream(int size);
      // Instance Methods
      public synchronized void reset();
      public int size( );
      public synchronized byte[] toByteArray();
      public String toString();
      public String toString(int hibyte);            // Deprecated in 1.1
      public String toString(String enc);            // New in 1.1
      public synchronized void write(int b);
      public synchronized void write(byte[] b, int off, int len);
      public synchronized void writeTo(OutputStream out);
    }

## Variables

### buf

#### protected byte[] buf

Description

  The buffer that holds data for this stream.

### count

#### protected int count

Description

  A placeholder that marks the end of the data in the buffer.

## Constructors

### ByteArrayOutputStream

#### public ByteArrayOutputStream()

Description

  This constructor creates a `ByteArrayOutputStream` with an internal buffer that has a default size of 32 bytes. The buffer grows automatically as data is written to the stream.

#### public ByteArrayOutputStream(int size)

Parameters

  `size`

    The initial buffer size.

Description

  This constructor creates a `ByteArrayOutputStream` with an internal buffer that has a size of `size` bytes. The buffer grows automatically as data is written to the stream.

## Instance Methods

### reset

#### public synchronized void reset()

Description

  This method discards the current contents of the buffer and resets the position of the stream to zero. Subsequent data is written starting at the beginning of the array.

### size

#### public int size()

Description

  This method returns the number of bytes currently stored in this object's internal buffer. It is a count of the number of bytes that have been written to the stream.

### toByteArray

#### public synchronized byte[] toByteArray()

Returns

  A copy of the data that has been written to this `ByteArrayOutputStream`.

Description

  This method copies the data in the internal array and returns a reference to the copy. The returned array is as long as the data that has been written to the stream, i.e., the same as `size()`.

### toString

#### public String toString()

Returns

  A copy of the data that has been written to this `ByteArrayOutputStream`.

Overrides

  `Object.toString()`

Description

  This method returns a reference to a `String` object that contains a copy of the bytes currently stored in this object's internal buffer. The bytes are assumed to represent characters in the encoding that is customary for the native platform, so the bytes are converted to Unicode characters based on that assumption.

#### public String toString(int hibyte)

Availability

  Deprecated as of JDK 1.1

Parameters

  `hibyte`

    A value to use as the high byte of each character.

Returns

  A copy of the data that has been written to this `ByteArrayOutputStream`, where each character in the string has a high byte of `hibyte` and a low byte taken from the corresponding byte in the array.

Description

  This method provides a way to convert from bytes to characters. As of 1.1, it is deprecated and replaced with `toString(String)`.

####

     public String toString(String enc) throws UnsupportedEncodingException

Availability

  New as of JDK 1.1

Parameters

  `enc`

    The encoding scheme to use.

Returns

  A copy of the data that has been written to this `ByteArrayOutputStream`, converted from bytes to characters via the named encoding scheme `enc`.

Throws

  `UnsupportedEncodingException`

    The specified encoding is not supported.

Description

  This method returns a Java `String` created from the byte array of this stream. The conversion is performed according to the encoding scheme `enc`.

### write

#### public synchronized void write(int b)

Parameters

  `b`

    The value to write.

Overrides

  `OutputStream.write(int)`

Description

  This method writes the low-order 8 bits of the given value into the internal array. If the array is full, a larger array is allocated.

#### public synchronized void write(byte b[], int off, int len)

Parameters

  `b`

    The array to copy from.

  `off`

    Offset into the byte array.

  `len`

    Number of bytes to write.

Overrides

  `OutputStream.write(byte[], int, int)`

Description

  This method copies `len` bytes to this object's internal array from `b`, starting `oset` elements from the beginning of the supplied array `b`. If the internal array is full, a larger array is allocated.

### writeTo

####

     public synchronized void writeTo(OutputStream out) throws IOException

Parameters

  `out`

    The destination stream.

Throws

  `IOException`

    If any kind of I/O error occurs.

Description

  This method writes the contents of this object's internal buffer to the given `OutputStream`. All the data that has been written to this `ByteArrayOutputStream` is written to `out`.

## Inherited Methods

Method | Inherited From | Method | Inherited From
--- | --- | --- | ---
`clone()` | `Object` | `close()` | `OutputStream`
`equals(Object)` | `Object` | `finalize()` | `Object`
`flush()` | `OutputStream` | `getClass()` | `Object`
`hashCode()` | `Object` | `notify()` | `Object`
`notifyAll()` | `Object` | `wait()` | `Object`
`wait(long)` | `Object` | `wait(long, int)` | `Object`
`write(byte[])` | `OutputStream` |  |

## See Also

`IOException`, `OutputStream`, `String`, `UnsupportedEncodingException`

ByteArrayInputStream |  | CharArrayReader