Class SynchronousChannel

java.lang.Object
EDU.oswego.cs.dl.util.concurrent.SynchronousChannel
All Implemented Interfaces:
BoundedChannel, Channel, Puttable, Takable

public class SynchronousChannel extends Object implements BoundedChannel
A rendezvous channel, similar to those used in CSP and Ada. Each put must wait for a take, and vice versa. Synchronous channels are well suited for handoff designs, in which an object running in one thread must synch up with an object running in another thread in order to hand it some information, event, or task.

If you only need threads to synch up without exchanging information, consider using a Barrier. If you need bidirectional exchanges, consider using a Rendezvous.

[ Introduction to this package. ]

See Also:
  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    protected static class 
    Simple FIFO queue class to hold waiting puts/takes.
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    protected static final Object
    Special marker used in queue nodes to indicate that the thread waiting for a change in the node has timed out or been interrupted.
    protected final SynchronousChannel.Queue
     
    protected final SynchronousChannel.Queue
     
  • Constructor Summary

    Constructors
    Constructor
    Description
     
  • Method Summary

    Modifier and Type
    Method
    Description
    int
    Return the maximum number of elements that can be held.
    boolean
    offer(Object x, long msecs)
    Place item in channel only if it can be accepted within msecs milliseconds.
    Return, but do not remove object at head of Channel, or null if it is empty.
    poll(long msecs)
    Return and remove an item from channel only if one is available within msecs milliseconds.
    void
    Place item in the channel, possibly waiting indefinitely until it can be accepted.
    Return and remove an item from channel, possibly waiting indefinitely until such an item exists.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  • Field Details

    • CANCELLED

      protected static final Object CANCELLED
      Special marker used in queue nodes to indicate that the thread waiting for a change in the node has timed out or been interrupted.
    • waitingPuts

      protected final SynchronousChannel.Queue waitingPuts
    • waitingTakes

      protected final SynchronousChannel.Queue waitingTakes
  • Constructor Details

    • SynchronousChannel

      public SynchronousChannel()
  • Method Details

    • capacity

      public int capacity()
      Description copied from interface: BoundedChannel
      Return the maximum number of elements that can be held.
      Specified by:
      capacity in interface BoundedChannel
      Returns:
      zero -- Synchronous channels have no internal capacity.
    • peek

      public Object peek()
      Description copied from interface: Channel
      Return, but do not remove object at head of Channel, or null if it is empty.
      Specified by:
      peek in interface Channel
      Returns:
      null -- Synchronous channels do not hold contents unless actively taken
    • put

      public void put(Object x) throws InterruptedException
      Description copied from interface: Channel
      Place item in the channel, possibly waiting indefinitely until it can be accepted. Channels implementing the BoundedChannel subinterface are generally guaranteed to block on puts upon reaching capacity, but other implementations may or may not block.
      Specified by:
      put in interface Channel
      Specified by:
      put in interface Puttable
      Parameters:
      x - the element to be inserted. Should be non-null.
      Throws:
      InterruptedException - if the current thread has been interrupted at a point at which interruption is detected, in which case the element is guaranteed not to be inserted. Otherwise, on normal return, the element is guaranteed to have been inserted.
    • take

      public Object take() throws InterruptedException
      Description copied from interface: Channel
      Return and remove an item from channel, possibly waiting indefinitely until such an item exists.
      Specified by:
      take in interface Channel
      Specified by:
      take in interface Takable
      Returns:
      some item from the channel. Different implementations may guarantee various properties (such as FIFO) about that item
      Throws:
      InterruptedException - if the current thread has been interrupted at a point at which interruption is detected, in which case state of the channel is unchanged.
    • offer

      public boolean offer(Object x, long msecs) throws InterruptedException
      Description copied from interface: Channel
      Place item in channel only if it can be accepted within msecs milliseconds. The time bound is interpreted in a coarse-grained, best-effort fashion.
      Specified by:
      offer in interface Channel
      Specified by:
      offer in interface Puttable
      Parameters:
      x - the element to be inserted. Should be non-null.
      msecs - the number of milliseconds to wait. If less than or equal to zero, the method does not perform any timed waits, but might still require access to a synchronization lock, which can impose unbounded delay if there is a lot of contention for the channel.
      Returns:
      true if accepted, else false
      Throws:
      InterruptedException - if the current thread has been interrupted at a point at which interruption is detected, in which case the element is guaranteed not to be inserted (i.e., is equivalent to a false return).
    • poll

      public Object poll(long msecs) throws InterruptedException
      Description copied from interface: Channel
      Return and remove an item from channel only if one is available within msecs milliseconds. The time bound is interpreted in a coarse grained, best-effort fashion.
      Specified by:
      poll in interface Channel
      Specified by:
      poll in interface Takable
      Parameters:
      msecs - the number of milliseconds to wait. If less than or equal to zero, the operation does not perform any timed waits, but might still require access to a synchronization lock, which can impose unbounded delay if there is a lot of contention for the channel.
      Returns:
      some item, or null if the channel is empty.
      Throws:
      InterruptedException - if the current thread has been interrupted at a point at which interruption is detected, in which case state of the channel is unchanged (i.e., equivalent to a null return).