- java.lang.Object
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- java.io.Reader
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- java.io.InputStreamReader
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- 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 specifiedcharset
. 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
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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.
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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.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Methods declared in class java.io.Reader
close, mark, markSupported, nullReader, read, read, reset, skip, transferTo
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Constructor Detail
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InputStreamReader
public InputStreamReader(InputStream in)
Creates an InputStreamReader that uses the default charset.- Parameters:
in
- An InputStream
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InputStreamReader
public InputStreamReader(InputStream in, String charsetName) throws UnsupportedEncodingException
Creates an InputStreamReader that uses the named charset.- Parameters:
in
- An InputStreamcharsetName
- The name of a supportedcharset
- Throws:
UnsupportedEncodingException
- If the named charset is not supported
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InputStreamReader
public InputStreamReader(InputStream in, Charset cs)
Creates an InputStreamReader that uses the given charset.- Parameters:
in
- An InputStreamcs
- A charset- Since:
- 1.4
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InputStreamReader
public InputStreamReader(InputStream in, CharsetDecoder dec)
Creates an InputStreamReader that uses the given charset decoder.- Parameters:
in
- An InputStreamdec
- A charset decoder- Since:
- 1.4
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Method Detail
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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 returnnull
if the stream has been closed.- Returns:
- The historical name of this encoding, or
null
if the stream has been closed - See Also:
Charset
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read
public int read() throws IOException
Reads a single character.- Overrides:
read
in classReader
- Returns:
- The character read, or -1 if the end of the stream has been reached
- Throws:
IOException
- If an I/O error occurs
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read
public int read(char[] cbuf, int offset, int length) throws IOException
Reads characters into a portion of an array.- Specified by:
read
in classReader
- Parameters:
cbuf
- Destination bufferoffset
- Offset at which to start storing characterslength
- 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 occursIndexOutOfBoundsException
- If an I/O error occurs
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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 classReader
- 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
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