FileDocCategorySizeDatePackage
InputStreamReader.javaAPI DocJava SE 6 API5566Tue Jun 10 00:25:32 BST 2008java.io

InputStreamReader

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 {@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.

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));
see
BufferedReader
see
InputStream
see
java.nio.charset.Charset
version
1.47, 05/11/17
author
Mark Reinhold
since
JDK1.1

Fields Summary
private final StreamDecoder
sd
Constructors Summary
public InputStreamReader(InputStream in)
Creates an InputStreamReader that uses the default charset.

param
in An InputStream

	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);
	}
    
public InputStreamReader(InputStream in, String charsetName)
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

	super(in);
	if (charsetName == null)
	    throw new NullPointerException("charsetName");
	sd = StreamDecoder.forInputStreamReader(in, this, charsetName);
    
public InputStreamReader(InputStream in, Charset cs)
Creates an InputStreamReader that uses the given charset.

param
in An InputStream
param
cs A charset
since
1.4
spec
JSR-51

        super(in);
	if (cs == null)
	    throw new NullPointerException("charset");
	sd = StreamDecoder.forInputStreamReader(in, this, cs);
    
public InputStreamReader(InputStream in, CharsetDecoder dec)
Creates an InputStreamReader that uses the given charset decoder.

param
in An InputStream
param
dec A charset decoder
since
1.4
spec
JSR-51

        super(in);
	if (dec == null)
	    throw new NullPointerException("charset decoder");
	sd = StreamDecoder.forInputStreamReader(in, this, dec);
    
Methods Summary
public voidclose()

	sd.close();
    
public java.lang.StringgetEncoding()
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 {@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 null if the stream has been closed.

return
The historical name of this encoding, or null if the stream has been closed
see
java.nio.charset.Charset
revised
1.4
spec
JSR-51

	return sd.getEncoding();
    
public intread()
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

        return sd.read();
    
public intread(char[] cbuf, int offset, int length)
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

	return sd.read(cbuf, offset, length);
    
public booleanready()
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

	return sd.ready();