Module java.base
Package java.io

Class 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

    • Constructor Detail

      • InputStreamReader

        public InputStreamReader​(InputStream in)
        Creates an InputStreamReader that uses the default charset.
        Parameters:
        in - An InputStream

      • 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

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