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java.io
Class InputStreamReader

java.lang.Object
  extended by java.io.Reader
      extended by java.io.InputStreamReader
All Implemented Interfaces:
Closeable, Readable
Direct Known Subclasses:
FileReader

public class InputStreamReader
extends Reader

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));
 

Since:
JDK1.1
See Also:
BufferedReader, InputStream, Charset

Field Summary
 
Fields inherited from class java.io.Reader
lock
 
Constructor Summary
InputStreamReader(InputStream in)
          Creates an InputStreamReader that uses the default charset.
InputStreamReader(InputStream in, Charset cs)
          Creates an InputStreamReader that uses the given charset.
InputStreamReader(InputStream in, CharsetDecoder dec)
          Creates an InputStreamReader that uses the given charset decoder.
InputStreamReader(InputStream in, String charsetName)
          Creates an InputStreamReader that uses the named charset.
 
Method Summary
 void close()
          Closes the stream and releases any system resources associated with it.
 String getEncoding()
          Returns the name of the character encoding being used by this stream.
 int read()
          Reads a single character.
 int read(char[] cbuf, int offset, int length)
          Reads characters into a portion of an array.
 boolean ready()
          Tells whether this stream is ready to be read.
 
Methods inherited from class java.io.Reader
mark, markSupported, read, 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)
Creates an InputStreamReader that uses the default charset.

Parameters:
in - An InputStream

InputStreamReader

public InputStreamReader(InputStream in,
                         String charsetName)
                  throws UnsupportedEncodingException
Creates an InputStreamReader that uses the named charset.

Parameters:
in - An InputStream
charsetName - The name of a supported charset
Throws:
UnsupportedEncodingException - If the named charset is not supported

InputStreamReader

public InputStreamReader(InputStream in,
                         Charset cs)
Creates an InputStreamReader that uses the given charset.

Parameters:
in - An InputStream
cs - A charset
Since:
1.4
spec
JSR-51

InputStreamReader

public InputStreamReader(InputStream in,
                         CharsetDecoder dec)
Creates an InputStreamReader that uses the given charset decoder.

Parameters:
in - An InputStream
dec - A charset decoder
Since:
1.4
spec
JSR-51
Method Detail

getEncoding

public String getEncoding()
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.

Returns:
The historical name of this encoding, or null if the stream has been closed
See Also:
Charset
spec
JSR-51
revised
1.4

read

public int read()
         throws IOException
Reads 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 offset,
                int length)
         throws IOException
Reads characters into a portion of an array.

Specified by:
read in class Reader
Parameters:
cbuf - Destination buffer
offset - Offset at which to start storing characters
length - 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
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.

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
Description copied from class: Reader
Closes the stream and releases any system resources associated with it. Once the stream has been closed, further read(), ready(), mark(), reset(), or skip() invocations will throw an IOException. Closing a previously closed stream has no effect.

Specified by:
close in interface Closeable
Specified by:
close in class Reader
Throws:
IOException - If an I/O error occurs

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