Class InputStreamReader

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

All Implemented Interfaces:: Closeable, AutoCloseable, 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:: 1.1
See Also:: BufferedReader, InputStream, Charset

Field Summary

Fields declared in class java.io.Reader

lock

Constructor Summary

Constructors
Constructor	Description
`InputStreamReader(InputStream in)`	Creates an InputStreamReader that uses the default charset.
`InputStreamReader(InputStream in, String charsetName)`	Creates an InputStreamReader that uses the named 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.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`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 declared in class java.io.Reader

close, mark, markSupported, nullReader, read, read, reset, skip, transferTo

Methods declared in 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

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

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

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; IndexOutOfBoundsException - 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