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package java.io;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import sun.nio.cs.StreamDecoder;
An InputStreamReader is a bridge from byte streams to character streams: It reads bytes and decodes them into characters using a specified charset. The charset that it uses may be specified by name or may be given explicitly, or the platform's default charset 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));
Author: Mark Reinhold See Also: Since: 1.1
/**
* An InputStreamReader is a bridge from byte streams to character streams: It
* reads bytes and decodes them into characters using a specified {@link
* java.nio.charset.Charset charset}. The charset that it uses
* may be specified by name or may be given explicitly, or the platform's
* default charset may be accepted.
*
* <p> 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.
*
* <p> For top efficiency, consider wrapping an InputStreamReader within a
* BufferedReader. For example:
*
* <pre>
* BufferedReader in
* = new BufferedReader(new InputStreamReader(System.in));
* </pre>
*
* @see BufferedReader
* @see InputStream
* @see java.nio.charset.Charset
*
* @author Mark Reinhold
* @since 1.1
*/
public class InputStreamReader extends Reader {
private final StreamDecoder sd;
Creates an InputStreamReader that uses the default charset.
Params: - in – An InputStream
/**
* Creates an InputStreamReader that uses the default charset.
*
* @param in An InputStream
*/
public InputStreamReader(InputStream in) {
super(in);
try {
sd = StreamDecoder.forInputStreamReader(in, this, (String)null); // ## check lock object
} catch (UnsupportedEncodingException e) {
// The default encoding should always be available
throw new Error(e);
}
}
Creates an InputStreamReader that uses the named charset.
Params: - in –
An InputStream
- charsetName – The name of a supported
charset
Throws: - UnsupportedEncodingException –
If the named charset is not supported
/**
* Creates an InputStreamReader that uses the named charset.
*
* @param in
* An InputStream
*
* @param charsetName
* The name of a supported
* {@link java.nio.charset.Charset charset}
*
* @exception UnsupportedEncodingException
* If the named charset is not supported
*/
public InputStreamReader(InputStream in, String charsetName)
throws UnsupportedEncodingException
{
super(in);
if (charsetName == null)
throw new NullPointerException("charsetName");
sd = StreamDecoder.forInputStreamReader(in, this, charsetName);
}
Creates an InputStreamReader that uses the given charset.
Params: - in – An InputStream
- cs – A charset
Since: 1.4 @spec JSR-51
/**
* Creates an InputStreamReader that uses the given charset.
*
* @param in An InputStream
* @param cs A charset
*
* @since 1.4
* @spec JSR-51
*/
public InputStreamReader(InputStream in, Charset cs) {
super(in);
if (cs == null)
throw new NullPointerException("charset");
sd = StreamDecoder.forInputStreamReader(in, this, cs);
}
Creates an InputStreamReader that uses the given charset decoder.
Params: - in – An InputStream
- dec – A charset decoder
Since: 1.4 @spec JSR-51
/**
* Creates an InputStreamReader that uses the given charset decoder.
*
* @param in An InputStream
* @param dec A charset decoder
*
* @since 1.4
* @spec JSR-51
*/
public InputStreamReader(InputStream in, CharsetDecoder dec) {
super(in);
if (dec == null)
throw new NullPointerException("charset decoder");
sd = StreamDecoder.forInputStreamReader(in, this, dec);
}
Returns the name of the character encoding being used by this stream.
If the encoding has an historical name then that name is returned;
otherwise the encoding's canonical name is returned.
If this instance was created with the InputStreamReader(InputStream, String) constructor then the returned name, being unique for the encoding, may differ from the name passed to the constructor. This method will return null if the
stream has been closed.
See Also: Returns: The historical name of this encoding, or
null if the stream has been closed @revised 1.4 @spec JSR-51
/**
* Returns the name of the character encoding being used by this stream.
*
* <p> If the encoding has an historical name then that name is returned;
* otherwise the encoding's canonical name is returned.
*
* <p> If this instance was created with the {@link
* #InputStreamReader(InputStream, String)} constructor then the returned
* name, being unique for the encoding, may differ from the name passed to
* the constructor. This method will return <code>null</code> if the
* stream has been closed.
* </p>
* @return The historical name of this encoding, or
* <code>null</code> if the stream has been closed
*
* @see java.nio.charset.Charset
*
* @revised 1.4
* @spec JSR-51
*/
public String getEncoding() {
return sd.getEncoding();
}
Reads a single character.
Throws: - IOException – If an I/O error occurs
Returns: The character read, or -1 if the end of the stream has been
reached
/**
* Reads a single character.
*
* @return The character read, or -1 if the end of the stream has been
* reached
*
* @exception IOException If an I/O error occurs
*/
public int read() throws IOException {
return sd.read();
}
Reads characters into a portion of an array.
Params: - cbuf – Destination buffer
- offset – Offset at which to start storing characters
- length – Maximum number of characters to read
Throws: - IOException – If an I/O error occurs
- IndexOutOfBoundsException – {@inheritDoc}
Returns: The number of characters read, or -1 if the end of the
stream has been reached
/**
* Reads characters into a portion of an array.
*
* @param cbuf Destination buffer
* @param offset Offset at which to start storing characters
* @param length Maximum number of characters to read
*
* @return The number of characters read, or -1 if the end of the
* stream has been reached
*
* @exception IOException If an I/O error occurs
* @exception IndexOutOfBoundsException {@inheritDoc}
*/
public int read(char cbuf[], int offset, int length) throws IOException {
return sd.read(cbuf, offset, length);
}
Tells 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.
Throws: - IOException – If an I/O error occurs
/**
* Tells 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.
*
* @exception IOException If an I/O error occurs
*/
public boolean ready() throws IOException {
return sd.ready();
}
public void close() throws IOException {
sd.close();
}
}