Chapter 11
The java.io Package

CharArrayReader

Name

CharArrayReader

Synopsis

Class Name:

java.io.CharArrayReader

Superclass:

java.io.Reader

Immediate Subclasses:

None

Interfaces Implemented:

None

Availability:

New as of JDK 1.1

The CharArrayReader class represents a stream whose data comes from a character array. This class is similar to ByteArrayInputStream, but it deals with a Java character stream rather than a byte stream. Furthermore, this class supports marking a position in the stream, which ByteArrayInputStream does not.

The position of the end of the stream depends on the constructor used. If the CharArrayReader(char[] buf) constructor is used, the end of the stream is the end of the character array. If the CharArrayReader(char[] 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.CharArrayReader extends java.io.Reader {
  // Variables
  protected char[] buf;
  protected int count;
  protected int markedPos;
  protected int pos;
  // Constructors
  public CharArrayReader(char[] buf);
  public CharArrayReader(char[] buf, int offset, int length);
  // Instance Methods
  public void close();
  public void mark(int readAheadLimit);
  public boolean markSupported();
  public int read();
  public int read(char[] b, int off, int len);
  public boolean ready();
  public void reset();
  public long skip(long n);
}

Variables

buf

protected char[] buf

Description: The buffer represented by this reader.

count

protected int count

Description: The size of the buffer, or in other words, the length of the array.

markedPos

protected int markedPos

Description: The buffer position when mark() was called. If mark() has not been called, this variable is 0.

pos

protected int pos

Description: The current position in the buffer.

Constructors

CharArrayReader

public CharArrayReader(char[] buf)

Parameters

buf: The reader source.

Description

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

public CharArrayReader(char[] buf, int offset, int length)

Parameters

buf

The reader source.

offset

An offset into the array.

length

The number of bytes to read.

Description

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

Instance Methods

close

public void close()

Overrides

Reader.close()

Description

This method closes the reader by removing the link between this CharArrayReader and the array it was created with.

mark

public void mark(int readAheadLimit) throws IOException

Parameters

readAheadLimit: The maximum number of characters that can be read before the saved position becomes invalid.

Throws

IOException: If the stream is closed or any other kind of I/O error occurs.

Overrides

Reader.mark(int)

Description

This method causes the CharArrayReader to remember its current position. A subsequent call to reset() causes the object to return to that saved position, and thus reread a portion of the buffer. Because the data for this stream comes from a char array, there is no limit on reading ahead, so readAheadLimit is ignored.

markSupported

public boolean markSupported()

Returns

The boolean value true.

Overrides

Reader.markSupported()

Description

This method returns true to indicate that this class supports mark() and reset().

read

public int read() throws IOException

Returns

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

Throws

IOException: If the stream is closed or any other kind of I/O error occurs.

Overrides

Reader.read()

Description

This method returns the next character in the array.

public int read(char[] b, int off, int len) throws IOException

Parameters

b

An array of characters to be filled from the stream.

off

An offset into the character array.

len

The number of characters to read.

Returns

The actual number of characters read or -1 if the end of the stream is encountered immediately.

Throws

IOException: If the stream is closed or any other kind of I/O error occurs.

Overrides

Reader.read(char[], int, int)

Description

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

ready

public boolean ready() throws IOException

Returns

A boolean value that indicates whether the stream is ready to be read.

Throws

IOException: If the stream is closed or any other kind of I/O error occurs.

Overrides

Reader.ready()

Description

If there is any data left to be read from the character array, this method returns true.

reset

public void reset() throws IOException

Throws

IOException: If the stream is closed or any other kind of I/O error occurs.

Overrides

Reader.reset()

Description

This method resets the position of the CharArrayReader to the position that was saved by calling the mark() method. If mark() has not been called, the CharArrayReader is reset to read from the beginning of the array.

skip

public long skip(long n) throws IOException

Parameters

n: The number of characters to skip.

Returns

The actual number of characters skipped.

Throws

IOException: If the stream is closed or any other kind of I/O error occurs.

Overrides

Reader.skip()

Description

This method skips n characters 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`	`equals (Object)`	`Object`
`finalize()`	`Object`	`getClass()`	`Object`
`hashCode()`	`Object`	`notify()`	`Object`
`notifyAll()`	`Object`	`read(char[])`	`Reader`
`toString()`	`Object`	`wait()`	`Object`
`wait(long)`	`Object`	`wait(long, int)`	`Object`