Package EDU.oswego.cs.dl.util.concurrent
Class SynchronousChannel
- java.lang.Object
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- EDU.oswego.cs.dl.util.concurrent.SynchronousChannel
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- 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.
- See Also:
CyclicBarrier
,Rendezvous
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Nested Class Summary
Nested Classes Modifier and Type Class Description protected static class
SynchronousChannel.Queue
Simple FIFO queue class to hold waiting puts/takes.
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Field Summary
Fields Modifier and Type Field Description protected static 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.protected SynchronousChannel.Queue
waitingPuts
protected SynchronousChannel.Queue
waitingTakes
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Constructor Summary
Constructors Constructor Description SynchronousChannel()
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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.
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Field Detail
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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.
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waitingPuts
protected final SynchronousChannel.Queue waitingPuts
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waitingTakes
protected final SynchronousChannel.Queue waitingTakes
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Method Detail
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capacity
public int capacity()
Description copied from interface:BoundedChannel
Return the maximum number of elements that can be held.- Specified by:
capacity
in interfaceBoundedChannel
- Returns:
- zero -- Synchronous channels have no internal capacity.
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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.
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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 interfaceChannel
- Specified by:
put
in interfacePuttable
- 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.
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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 interfaceChannel
- Specified by:
take
in interfaceTakable
- 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.
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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 interfaceChannel
- Specified by:
offer
in interfacePuttable
- 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).
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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 interfaceChannel
- Specified by:
poll
in interfaceTakable
- 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).
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