java.io
Class InputStreamReader

java.lang.Object
  java.io.Reader
      java.io.InputStreamReader

Direct Known Subclasses:

FileReader

public class InputStreamReader

extends Reader

An InputStreamReader is a bridge from byte streams to character streams: It reads bytes and translates them into characters according to a specified character encoding. The encoding that it uses may be specified by name, or the platform's default encoding may be accepted.

Each invocation of one of an InputStreamReader's read() methods may cause one or more bytes to be read from the underlying byte-input stream. To enable the efficient conversion of bytes to characters, more bytes may be read ahead from the underlying stream than are necessary to satisfy the current read operation.

For top efficiency, consider wrapping an InputStreamReader within a BufferedReader. For example:

 BufferedReader in
   = new BufferedReader(new InputStreamReader(System.in));
 

Since:

JDK1.1

See Also:

BufferedReader, InputStream, Character encodings

Field Summary

Fields inherited from class java.io.Reader

lock

Constructor Summary

InputStreamReader(InputStream in)
Create an InputStreamReader that uses the default character encoding.

InputStreamReader(InputStream in, String enc)
Create an InputStreamReader that uses the named character encoding.

Method Summary

void	close() Close the stream.
String	getEncoding() Returns the canonical name of the character encoding being used by this stream.
int	read() Read a single character.
int	read(char[] cbuf, int off, int len) Read characters into a portion of an array.
boolean	ready() Tell whether this stream is ready to be read.

Methods inherited from class java.io.Reader

mark, markSupported, read, reset, skip

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

InputStreamReader

public InputStreamReader(InputStream in)

Create an InputStreamReader that uses the default character encoding.

Parameters:

in - An InputStream

InputStreamReader

public InputStreamReader(InputStream in,
                         String enc)
                  throws UnsupportedEncodingException

Create an InputStreamReader that uses the named character encoding.

Parameters:

in - An InputStream

enc - The name of a supported character encoding

Throws:

UnsupportedEncodingException - If the named encoding is not supported

Method Detail

getEncoding

public String getEncoding()

Returns the canonical name of the character encoding being used by this stream.

If this instance was created with the InputStreamReader(InputStream, String) constructor then the returned encoding name, being canonical, may differ from the encoding name passed to the constructor. This method may return null if the stream has been closed.

NOTE : In J2ME CDC, there is no concept of historical name, so only canonical name of character encoding is returned.

Returns:

a String representing the encoding name, or possibly null if the stream has been closed

See Also:

Character encodings

read

public int read()
         throws IOException

Read a single character.

Overrides:

read in class Reader

Returns:

The character read, or -1 if the end of the stream has been reached

Throws:

IOException - If an I/O error occurs

read

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

Read characters into a portion of an array.

Specified by:

read in class Reader

Parameters:

cbuf - Destination buffer

off - Offset at which to start storing characters

len - Maximum number of characters to read

Returns:

The number of characters read, or -1 if the end of the stream has been reached

Throws:

IOException - If an I/O error occurs

ready

public boolean ready()
              throws IOException

Tell whether this stream is ready to be read. An InputStreamReader is ready if its input buffer is not empty, or if bytes are available to be read from the underlying byte stream.

Overrides:

ready in class Reader

Returns:

True if the next read() is guaranteed not to block for input, false otherwise. Note that returning false does not guarantee that the next read will block.

Throws:

IOException - If an I/O error occurs

close

public void close()
           throws IOException

Close the stream.

Specified by:

close in class Reader

Throws:

IOException - If an I/O error occurs