Class SynchronousChannel

  • All Implemented Interfaces:
    BoundedChannel, Channel, Puttable, Takable

    public class SynchronousChannel
    extends java.lang.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:
    CyclicBarrier, Rendezvous
    • Nested Class Summary

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

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

      • CANCELLED

        protected static final java.lang.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.
    • Constructor Detail

      • SynchronousChannel

        public SynchronousChannel()
    • Method Detail

      • 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 java.lang.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​(java.lang.Object x)
                 throws java.lang.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:
        java.lang.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 java.lang.Object take()
                              throws java.lang.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:
        java.lang.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​(java.lang.Object x,
                             long msecs)
                      throws java.lang.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:
        java.lang.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 java.lang.Object poll​(long msecs)
                              throws java.lang.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:
        java.lang.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).