java.io.Reader Class Reference

Inheritance diagram for java.io.Reader:

Public Member Functions
abstract void	close () throws IOException
void	mark (int readLimit) throws IOException
boolean	markSupported ()
int	read () throws IOException
int	read (char[] buf) throws IOException
abstract int	read (char[] buf, int offset, int count) throws IOException
boolean	ready () throws IOException
void	reset () throws IOException
long	skip (long charCount) throws IOException

Protected Member Functions
	Reader ()
	Reader (Object lock)

Protected Attributes
Object	lock

Detailed Description

The base class for all readers. A reader is a means of reading data from a source in a character-wise manner. Some readers also support marking a position in the input and returning to this position later.

This abstract class does not provide a fully working implementation, so it needs to be subclassed, and at least the read(char[], int, int) and close() methods needs to be overridden. Overriding some of the non-abstract methods is also often advised, since it might result in higher efficiency.

Many specialized readers for purposes like reading from a file already exist in this package.

See also

Writer

Constructor & Destructor Documentation

Reader() [1/2]

java.io.Reader.Reader ( )

inlineprotected

Constructs a new

Reader 

with

this 

as the object used to synchronize critical sections.

Reader() [2/2]

java.io.Reader.Reader ( Object  lock )

inlineprotected

Constructs a new

Reader 

with

lock 

used to synchronize critical sections.

Parameters

lock	the Object used to synchronize critical sections.

Exceptions

NullPointerException

if lock is null .

Member Function Documentation

close()

abstract void java.io.Reader.close ( ) throws IOException

abstract

Closes this reader. Implementations of this method should free any resources associated with the reader.

Exceptions

IOException

if an error occurs while closing this reader.

mark()

void java.io.Reader.mark ( int  readLimit ) throws IOException

inline

Sets a mark position in this reader. The parameter

readLimit 

indicates how many characters can be read before the mark is invalidated. Calling

reset() 

will reposition the reader back to the marked position if

readLimit 

has not been surpassed.

This default implementation simply throws an

IOException 

; subclasses must provide their own implementation.

Parameters

readLimit

the number of characters that can be read before the mark is invalidated.

Exceptions

IllegalArgumentException	if readLimit < 0 .
IOException	if an error occurs while setting a mark in this reader.

See also

markSupported()

reset()

markSupported()

boolean java.io.Reader.markSupported ( )

inline

Indicates whether this reader supports the

mark() 

and

reset() 

methods. This default implementation returns

false 

.

Returns

always

false 

.

read() [1/3]

int java.io.Reader.read ( ) throws IOException

inline

Reads a single character from this reader and returns it as an integer with the two higher-order bytes set to 0. Returns -1 if the end of the reader has been reached.

Returns

the character read or -1 if the end of the reader has been reached.

Exceptions

IOException

if this reader is closed or some other I/O error occurs.

read() [2/3]

int java.io.Reader.read ( char []  buf ) throws IOException

inline

Reads characters from this reader and stores them in the character array

buf 

starting at offset 0. Returns the number of characters actually read or -1 if the end of the reader has been reached.

Parameters

buf	character array to store the characters read.

Returns

the number of characters read or -1 if the end of the reader has been reached.

Exceptions

IOException

if this reader is closed or some other I/O error occurs.

read() [3/3]

abstract int java.io.Reader.read ( char []  buf, int  offset, int  count  ) throws IOException

abstract

Reads at most

count 

characters from this reader and stores them at

offset 

in the character array

buf 

. Returns the number of characters actually read or -1 if the end of the reader has been reached.

Parameters

buf	the character array to store the characters read.
offset	the initial position in buffer to store the characters read from this reader.
count	the maximum number of characters to read.

Returns

the number of characters read or -1 if the end of the reader has been reached.

Exceptions

IOException

if this reader is closed or some other I/O error occurs.

ready()

boolean java.io.Reader.ready ( ) throws IOException

inline

Indicates whether this reader is ready to be read without blocking. Returns

true 

if this reader will not block when

read 

is called,

false 

if unknown or blocking will occur. This default implementation always returns

false 

.

Returns

always

false 

.

Exceptions

IOException

if this reader is closed or some other I/O error occurs.

See also

read()

#read(char[])

#read(char[], int, int)

reset()

void java.io.Reader.reset ( ) throws IOException

inline

Resets this reader's position to the last

mark() 

location. Invocations of

read() 

and

skip() 

will occur from this new location. If this reader has not been marked, the behavior of

reset() 

is implementation specific. This default implementation throws an

IOException 

.

Exceptions

IOException

always thrown in this default implementation.

See also

mark(int)

markSupported()

skip()

long java.io.Reader.skip ( long  charCount ) throws IOException

inline

Skips

charCount 

characters in this reader. Subsequent calls of

read 

methods will not return these characters unless

reset 

is used. This method may perform multiple reads to read

charCount 

characters.

Returns

the number of characters actually skipped.

Exceptions

IllegalArgumentException	if charCount < 0 .
IOException	if this reader is closed or some other I/O error occurs.

See also

mark(int)

markSupported()

reset()

Member Data Documentation

lock

Object java.io.Reader.lock

protected

The object used to synchronize access to the reader.

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The documentation for this class was generated from the following file:

• src/java/io/Reader.java