[Chapter 11] ByteArrayInputStream

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| Chapter 11 The java.io Package |

# ByteArrayInputStream

## Name

ByteArrayInputStream

## Synopsis

Class Name:

  `java.io.ByteArrayInputStream`

Superclass:

  `java.io.InputStream`

Immediate Subclasses:

  None

Interfaces Implemented:

  None

Availability:

  JDK 1.0 or later

## Description

A `ByteArrayInputStream` is a stream whose data comes from a byte array. None of the methods of this class throw an `IOException` because the data comes from an array instead of an actual I/O device. This class does not support the ability to mark a position in the stream. A call to `reset()`, however, does position the stream at the beginning of the byte array.

The position of the end of the stream depends on the constructor used. If the `ByteArrayInputStream(byte[] buf)` constructor is used, the end of the stream is the end of the byte array. If the `ByteArrayInputStream(byte[] buf, int offset, int length)` constructor is used, the end of the stream is reached at the index given by `offset+length`.

## Class Summary

    public class java.io.ByteArrayInputStream extends java.io.InputStream {
      // Variables
      protected byte[] buf;
      protected int count;
      protected int pos;
      // Constructors
      public ByteArrayInputStream(byte[] buf);
      public ByteArrayInputStream(byte[] buf, int offset, int length);
      // Instance Methods
      public synchronized int available();
      public synchronized int read();
      public synchronized int read(byte[] b, int off, int len);
      public synchronized void reset();
      public synchronized long skip(long n);
    }

## Variables

### buf

#### protected byte[] buf

Description

  The buffer represented by this stream.

### count

#### protected int count

Description

  A placeholder that marks the end of the data this `ByteArrayInputStream` represents.

### pos

#### protected int pos

Description

  The current position in the buffer.

## Constructors

### ByteArrayInputStream

#### public ByteArrayInputStream(byte[] buf)

Parameters

  `buf`

    The stream source.

Description

  This constructor creates a `ByteArrayInputStream` object that uses the given array of bytes as its data source. The data is not copied, so changes made to the array affect the data the `ByteArrayInputStream` returns.

#### public ByteArrayInputStream(byte[] buf, int offset, int length)

Parameters

  `buf`

    The stream source.

  `offset`

    An index into the buffer where the stream should begin.

  `length`

    The number of bytes to read.

Description

  This constructor creates a `ByteArrayInputStream` that uses, as its data source, `length` bytes in a given array of bytes, starting at `offset` bytes from the beginning of the array. The data is not copied, so changes made to the array affect the data the `ByteArrayInputStream` returns.

## Instance Methods

### available

#### public synchronized int available()

Returns

  The number of bytes remaining to be read in the array.

Overrides

  `InputStream.available()`

Description

  This method returns the number of bytes remaining to be read in the byte array.

### read

#### public synchronized int read()

Returns

  The next byte or `-1` if the end of the stream is encountered.

Overrides

  `InputStream.read()`

Description

  This method returns the next byte in the array.

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

Parameters

  `b`

    An array to read bytes into.

  `off`

    An offset into `b`.

  `len`

    The number of bytes to read.

Returns

  The number of bytes read or `-1` if the end of the stream is encountered.

Overrides

  `InputStream.read(byte[], int, int)`

Description

  This method copies up to `len` bytes from its internal byte array into the given array `b`, starting at index `off`.

### reset

#### public synchronized void reset()

Overrides

  `InputStream.reset()`

Description

  This method resets the position of the input stream to the beginning of the byte array. If you specified an offset into the array, you might expect this method to reset the position to where you first started reading from the stream, but that is not the case.

### skip

#### public synchronized long skip(long n)

Parameters

  `n`

    The number of bytes to skip.

Returns

  The number of bytes skipped.

Overrides

  `InputStream.skip()`

Description

  This method skips `n` bytes of input. If you try to skip past the end of the array, the stream is positioned at the end of the array.

## Inherited Methods

Method | Inherited From | Method | Inherited From
--- | --- | --- | ---
`clone()` | `Object` | `close()` | `InputStream`
`equals (Object)` | `Object` | `finalize()` | `Object`
`getClass()` | `Object` | `hashCode()` | `Object`
`mark(int)` | `InputStream` | `markSupported ()` | `InputStream`
`notify()` | `Object` | `notifyAll()` | `Object`
`read(byte[])` | `InputStream` | `toString()` | `Object`
`wait()` | `Object` | `wait(long)` | `Object`
`wait(long, int)` | `Object` |  |

## See Also

`InputStream`, `String`

BufferedWriter |  | ByteArrayOutputStream