Chapter 11
The java.io Package

ByteArrayInputStream

Name

Synopsis

Class Name:

java.io.ByteArrayInputStream

Superclass:

java.io.InputStream

Immediate Subclasses:

None

Interfaces Implemented:

None

Availability:

JDK 1.0 or later

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`