PipedReader (Java SE 9 & JDK 9 )
Keywords: java.io.PipedReader class

Module java.base
Package java.io

## Class PipedReader

- java.lang.Object
- - java.io.Reader
  - - java.io.PipedReader

- All Implemented Interfaces:
    `Closeable`, `AutoCloseable`, `Readable`

      public class PipedReader
      extends Reader

  Piped character-input streams.
  Since:
    1.1

- - ### Field Summary

    - ### Fields inherited from class java.io.Reader

      `lock`

  - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `PipedReader​()` | Creates a `PipedReader` so that it is not yet connected.
    `PipedReader​(int pipeSize)` | Creates a `PipedReader` so that it is not yet `connected` and uses the specified pipe size for the pipe's buffer.
    `PipedReader​(PipedWriter src)` | Creates a `PipedReader` so that it is connected to the piped writer `src`.
    `PipedReader​(PipedWriter src, int pipeSize)` | Creates a `PipedReader` so that it is connected to the piped writer `src` and uses the specified pipe size for the pipe's buffer.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `void` | `close​()` | Closes this piped stream and releases any system resources associated with the stream.
    `void` | `connect​(PipedWriter src)` | Causes this piped reader to be connected to the piped writer `src`.
    `int` | `read​()` | Reads the next character of data from this piped stream.
    `int` | `read​(char[] cbuf, int off, int len)` | Reads up to `len` characters of data from this piped stream into an array of characters.
    `boolean` | `ready​()` | Tell whether this stream is ready to be read.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

    - ### Methods inherited from class java.io.Reader

      `mark, markSupported, read, read, reset, skip`

- - ### Constructor Detail

    - #### PipedReader

          public PipedReader​(PipedWriter src)
                      throws IOException

      Creates a `PipedReader` so that it is connected to the piped writer `src`. Data written to `src` will then be available as input from this stream.
      Parameters:
        `src` - the stream to connect to.
      Throws:
        `IOException` - if an I/O error occurs.

    - #### PipedReader

          public PipedReader​(PipedWriter src,
                             int pipeSize)
                      throws IOException

      Creates a `PipedReader` so that it is connected to the piped writer `src` and uses the specified pipe size for the pipe's buffer. Data written to `src` will then be available as input from this stream.
      Parameters:
        `src` - the stream to connect to.
        `pipeSize` - the size of the pipe's buffer.
      Throws:
        `IOException` - if an I/O error occurs.
        `IllegalArgumentException` - if `pipeSize <= 0`.
      Since:
        1.6

    - #### PipedReader

          public PipedReader​()

      Creates a `PipedReader` so that it is not yet connected. It must be connected to a `PipedWriter` before being used.

    - #### PipedReader

          public PipedReader​(int pipeSize)

      Creates a `PipedReader` so that it is not yet `connected` and uses the specified pipe size for the pipe's buffer. It must be connected to a `PipedWriter` before being used.
      Parameters:
        `pipeSize` - the size of the pipe's buffer.
      Throws:
        `IllegalArgumentException` - if `pipeSize <= 0`.
      Since:
        1.6

  - ### Method Detail

    - #### connect

          public void connect​(PipedWriter src)
                       throws IOException

      Causes this piped reader to be connected to the piped writer `src`. If this object is already connected to some other piped writer, an `IOException` is thrown.

      If `src` is an unconnected piped writer and `snk` is an unconnected piped reader, they may be connected by either the call:

          snk.connect(src)

      or the call:

          src.connect(snk)

      The two calls have the same effect.

      Parameters:
        `src` - The piped writer to connect to.
      Throws:
        `IOException` - if an I/O error occurs.

    - #### read

          public int read​()
                   throws IOException

      Reads the next character of data from this piped stream. If no character is available because the end of the stream has been reached, the value `-1` is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.
      Overrides:
        `read` in class `Reader`
      Returns:
        the next character of data, or `-1` if the end of the stream is reached.
      Throws:
        `IOException` - if the pipe is `broken`, `unconnected`, closed, or an I/O error occurs.

    - #### read

          public int read​(char[] cbuf,
                          int off,
                          int len)
                   throws IOException

      Reads up to `len` characters of data from this piped stream into an array of characters. Less than `len` characters will be read if the end of the data stream is reached or if `len` exceeds the pipe's buffer size. This method blocks until at least one character of input is available.
      Specified by:
        `read` in class `Reader`
      Parameters:
        `cbuf` - the buffer into which the data is read.
        `off` - the start offset of the data.
        `len` - the maximum number of characters read.
      Returns:
        the total number of characters read into the buffer, or `-1` if there is no more data because the end of the stream has been reached.
      Throws:
        `IOException` - if the pipe is `broken`, `unconnected`, closed, or an I/O error occurs.
        `IndexOutOfBoundsException` - If an I/O error occurs

    - #### ready

          public boolean ready​()
                        throws IOException

      Tell whether this stream is ready to be read. A piped character stream is ready if the circular buffer is not empty.
      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 the pipe is `broken`, `unconnected`, or closed.

    - #### close

          public void close​()
                     throws IOException

      Closes this piped stream and releases any system resources associated with the stream.
      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.