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(anInputStream));
Since:
1.1
See Also:

  • Field Summary

  • Constructor Summary

    Constructors

    Creates an InputStreamReader that uses the named charset.

    Creates an InputStreamReader that uses the given charset.

    Creates an InputStreamReader that uses the given charset decoder.

  • Method Summary

    void

    close()

    Closes the stream and releases any system resources associated with it.

    Returns the name of the character encoding being used by this stream.

    int

    read()

    Reads a single character.

    int

    read(char[] cbuf, int off, int len)

    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

  • Constructor Details

    • InputStreamReader

      Parameters:
      in - An InputStream
      See Also:

    • InputStreamReader

      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

      Creates an InputStreamReader that uses the given charset.

      Parameters:
      in - An InputStream
      cs - A charset
      Since:
      1.4

    • InputStreamReader

      Creates an InputStreamReader that uses the given charset decoder.

      Parameters:
      in - An InputStream
      dec - A charset decoder
      Since:
      1.4

  • Method Details

    • 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:

    • read

      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 off, int len) throws IOException

      Reads characters into a portion of an array. This method will block until some input is available, an I/O error occurs, or the end of the stream is reached.

      If len is zero, then no characters are read and 0 is returned; otherwise, there is an attempt to read at least one character. If no character is available because the stream is at its end, the value -1 is returned; otherwise, at least one character is read and stored into cbuf.

      Specified by:
      read in class Reader
      Parameters:
      cbuf - Destination buffer
      off - Offset at which to start storing characters
      len - Maximum number of characters to read
      Returns:
      The number of characters read, or -1 if the end of the stream has been reached
      Throws:
      IndexOutOfBoundsException - If off is negative, or len is negative, or len is greater than cbuf.length - off
      IOException - If an I/O error occurs

    • ready

      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

      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